Le Cognac by R. Lafon, J. Lafon and P. Couillaud (1958)

Follow along: IG @birectifier

Welcome to an abridged version of the famed Le Cognac. To complete the translation in a reasonable amount of time and make the reading swifter, I decided to not include quite a few photos and omitted a few chapters that mostly covered sales and marketing.

There are so many things to notice in this text and I got a great sense of admiration reading it. First is that Cognac distillers, for their best wines, are obsessed with the pacing of their stills and harnessing the inherent reflux of a pot still by employing very long times under heat. At one point, we even get a glimpse of a 22 hour still run! In my annotations, I mentioned the work about pot still reflux conducted in Australia which I first time digitized many years ago. Low and behold, it was in their bibliography! Who would have thought a student project at Roseworthy could influence a great Cognac scientist?

Cognac distillers are also wary of esterification. They do not believe, even with a pot still, extended time under heat, and ferments with very significant acidity, that they achieve much esterification in the still. This may be an important lesson for rum distillers who want to incorporate butyric acid but not really commit to the grand Jamaican process. They may not easily find the esterification they are looking for. Retorts may hold a bit of a secret. Cognac distillers are also obsessed with high value steam volatile congeners and so was Arroyo! However, this text never uses terms like tails waters. Even though Cognac distillers are particularly into distillation over lees, they are wary of free volatile acid and make a tails cut they call “seconds” so that the hearts fraction has a certain clarity without fattiness.

I had never heard of still cleaning routines that were so intensive but no doubt there are lessons that will help some people. Maybe some readers can bring forward first hand experience on working with dirty stills and regretting it.

The whole book basically never mentions fusel oil or higher alcohols and I’m wagering it does not appreciably enter their decision making. Their unrushed ferments no doubt give below average fusel oil for a budding yeast so it never becomes a concern like ultra fast sub 72 hour distillery ferments.

The analysis the authors conduct is nothing special and basically lagging for the era. Kervegant appears in their bibliography who mentions Arroyo’s work and described the birectifier, but they certainly never possessed one. They also do not practice any type of quantitative tasting which was practiced mainly by buyers at the time to understand spirits stretchability. They mention Ordinneau, Karl Micko appears in their bibliography, and again are enthusiastic about steam volatile congeners, but never get into the topic of Cognac oil, or non-saponifiable terpene-like congeners.

To relate what I’ve learned to my own work, many of the fission yeast spirits I’ve been analyzing with the birectifier are more like a brouillis than a complete spirit. I have mainly been concerned with assets and liabilities in the ferment, particularly rum oil. I would be well served by using their double distillation template. Some of my supposed “assets” may need reconsidered such as longer chain volatile acidity so that I can better understand the cut to seconds for a production scale spirit.

So much has probably happened in Cognac production since, but I do not know enough about their contemporary practices. Hopefully readers in the know can fill us in!

I am reminded of one of my favorite blog posts, Excise Anecdotes from the Arak Country, where the author tells the tale of his visit to Cognac, his revelation of terroir, and his wish to explore the idea in Sri Lanka. Others distillers are having their own revelations of terroir and no doubt spending time understanding the original category will help them out.

Le Cognac
Its Distillation

Monsieur Maurice HENNESSY



This our “country of promise”, benefits, among other things, from the effective help given to it by a number of eminent men.

Lovers no doubt of its horizons and light, they serve it in many areas with intelligence, constant dedication and total disinterestedness.

MM. René and Jean Lafon and Mr. Pierre Couillaud first asked me for a preface for their “Notes on Distillation in the Charentes”, (1), I do so all the more willingly as this is a new opportunity for me to tell them of all my admiration and gratitude for the passionate dedication with which they follow the life and issues of our region and its product.

(1) The third edition is entitled: “Cognac, its distillation”

My father had thought, many years ago, that the winegrower’s committee of the Cognac district should be concerned with the technical training of distillers, as well as that of winegrowers.

The work of MM. Lafon and Couillaud as professionals brings not only advice and lessons, but also explanations of their difficult art.

Never has it been more necessary to strive to do well.

Such a variety of products is offered in the world to consumers that only those for whom, over the years, care has been taken to avoid criticism, can hope to find a satisfactory sale.

In general, the public is infinitely more knowledgeable than we think. If there are few expert tasters, it is necessary to be convinced of this truth that the masses taste well and that they remember who wanted to deceive them.

This is true, I believe, that in all fields, production quality even more than the price is an essential factor, when it comes to maintaining, sales in export markets for a large number of years.

President of the Viticulture committee.
President of the Cognac chamber of commerce.


The eaux-de-vie of the Charentes, largely exported, represent an important element of prosperity for their area of production and a precious source of currency for our country.

A powerful commercial organization and the maintenance of high quality alone can continue to assure the Cognac of longevity.

The soil, the climate and the grape varieties used are considered to be the essential factors in the quality of Cognac; no less important, however, is the art of the distiller. Indeed, if it is not possible to make good Cognac with defective wine, it is also not uncommon to obtain a bad eau-de-vie with a good wine whose distillation is poorly conducted. It is also illusory to rely on aging to make a distillation defect occurs disappear, because time only accentuates the qualities such as eau-de-vie defects.

Distillation is less simple than is generally supposed. Indeed, if one consults a treatise on this question, one learns that, in the case of a mixture of three liquids, the passage of the volatile elements is subject to complex laws. When it comes to wine, the number of components is such that it becomes almost impossible to formulate laws.

With a plate column, it is possible, by following certain rules, to obtain a constant product. With a primitive device like the Charentais still, there are no longer any general rules, and the distiller must change his way of operating according to the wines used.

The absence of precise rules, initiative left to each distiller, thus make Charente distillation an art rather than a technique.

The notes gathered in the following pages, result in part from advice gathered from old distillers themselves guided by tasting specialists. They are also the result of repeated tests and analyzes.

These notes were written more particularly for young people who are new to the art of Cognac distillation, in order to provide them with some elements and principles on the proper functioning of boilers.

These concepts were supplemented by a summary of the various useful knowledge on distillation and alcoholometry.

René Lafon, Jean Lafon, Pierre Couillaud.
Station Viticole de Cognac.

Notes from the authors for the 3rd edition:

Favorable reception obtained by previous editions and feedback given to us prompted the addition of precise historical, economic and legal notes on cognac, as well as notions on Charentais wines, vintages, the aging of cognac and a chapter on cognac from a nutritional and therapeutic point of view.

We have included in this new text two articles by M. Coquillaud, director of the National Cognac Office, on the export of cognac and on the role of the National Cognac Office.

The additions made have led us to modify the title which has become: “Cognac, its distillation”.

Distillation over the centuries (1)

(1) For a more detailed study, consult the works of Dujardin and Delamain (see: bibliography, p. 195).

Most ancient peoples seem to have known alcohol. However, it was not until the Middle Ages that it was first studied by Arnaud de Villeneuve.

In 1250, this chemist attributed magical virtues to it, among which that of prolonging life, hence the name “Eau-de-vie”.

Alcohol, a real medicine, which was then perfumed with the aid of aromatic plants according to the data of the alchemists and to which new virtues were always attributed, ended up overflowing the pharmacopoeia; the use of it became common.

The distillation of wine does not seem to have developed in the Cognac region before the beginning of the 17th century. It became generalized in Aunis only around 1622 and around 1630 in Saintonge and Angoumois, as a result of the poor sales of wines charged with excessive taxes.

Devices used to distill eaux-de-vie were lost for a long time. Nevertheless, we can know that they were built according to the ancient models of the Greeks and the Arabs: It is the still in its simplest form, consisting of a vessel containing the wine, which is surmounted by a capital ending in an inclined spout , air-cooled. Only later, distillers had the idea of lengthening the spout of the marquee to pass through a tub of cold water, or of giving it the shape of a spiral to extend its contact with water. This is the elementary device still used to obtain Cognac: boiler, capital, swan neck, serpentine.

In the 17th century, outside the Charentes, the main focus was on obtaining large quantities of brandy at a low price. The furnace and boiler were constantly modified so that boiling could be obtained as quickly as possible. Several boilers were even installed on the same furnace to take advantage of all the heat in the hearth; the capital and the condenser were modified a hundred times to hasten condensation of the vapors, but the product obtained was not pleasant. The greatest effort of the manufacturers then turned to the art of making liqueurs, that is to say, hiding bad taste under pleasant scents.

During the 18th century, there was an evolution in favor of pure brandy consumption. From that time on, there was an uninterrupted effort to obtain “good-tasting” alcohols. It was therefore forbidden to make brandy with anything other than wine, but even made with wine, it retained an unpleasant burnt taste.

It was left to still manufacturers to find a design that could produce a tasty brandy, without the need to conduct several expensive successive distillations. The furnace was modified, which was most of the time poorly designed and caused the formation of burnt aroma by being too hot. Distillation in a water bath with steam was also tried, but the results were disappointing.

The chemists then focused their efforts on the “Moor’s head” or capital and especially on the Col de Cygne, which they lengthened more and more.

The same problems arose in of Europe. The English sought to reduce the expense resulting from successive distillations by making as many heatings as possible at the same time. They first emptied their still 5 to 6 times a day and soon managed to make 20, then 72 heatings in twenty-four hours!

Finally in 1800, Adam invented his rectifying design which would revolutionize this branch of commerce.

The problem seemed to be resolved. It wasn’t. The brandy no longer tasted bad, but it no longer had taste at all. With the foul smells gone so were all the pleasant scents of wine. The product thus obtained was bland and, in order to make it pleasant to drink, it had to be perfumed with aromatic plants. “We therefore arrived at the paradoxical result that after having perfumed the eaux-de-vie to dispel its bad taste, it was now necessary to perfume them to give them flavor”. So the liqueurs of yesteryear reappeared.

This is the vicious circle in which commonly consumed brandy has been trapped for centuries. However, Cognac has remained outside this vicious circle.

At the end of the 18th century, it was a product selected in France; outside of France its fame extends to Europe and the coasts of America.

In 1730, Cognac brandy was already an object of speculation. It also takes, it seems, the character of a limited product which has its supply and demand and almost a market price. At this time, the habit began to take hold in the Cognac region, to keep the eaux-de-vie, sometimes with the aim of making the most of them, sometimes as a result of poor sales due to the temporary shortage of cash.

The Charente winegrowers had indeed observed that the eau-de-vie did not lose quality if it was stored for a certain time, while waiting for the money losing harvests to increase its value. It was even quickly realized that, while waiting, not only was the brandy not suffering, but on the contrary was improving. With time, it acquired a mellow taste, a more refined, more penetrating bouquet, while the range of flavors was enriched in it; it also took on a beautiful and warm shade of gold, which made it more attractive.

At the end of the 18th century, we therefore began to keep the eaux-de-vie to age.

The origins of Cognac and the evolution of the Charentais vineyard (1).

(1) For the study of regional customs and traditions, consult the works of Delamain, Pons, Vivier and Guérive (see: bibliography, p. 195).

The origins:

In a letter to his friend Paulus, the Gallo-Roman poet Ausone already described the vine-covered slopes of Novenus pagus (region of Saintes) and from the 13th century the parchments report an active wine-making current passing through La Rochelle.

In the 14th century, a fairly prosperous current of trade had been established between the provinces of southwestern France, England and the Nordic countries. British, Dutch, Scandinavian and Hanseatic ships continued to come to stock up on wheat and salt on the Charente coasts, whose ports had been specially developed.

Thanks to proximity of Ocean ports and the Charente, then being very navigable, the wine trade quickly expanded. From La Rochelle, wines were shipped to England, Denmark and Norway. King Jean Sans Terre granted the Rochelais letters of protection for the sale of their wines in Flanders and the Netherlands. Jehan de Laudun tells us that in 1323 they consumed a lot of wines in Paris, among which those of La Rochelle were famous there.

Going up the course of the Charente, the Dutch appreciated the wines of the vineyards located at the gates of Cognac and shipped a large quantity to England, Holland and the Scandinavian countries. These white, sparkling and fragrant wines came from “Colombard”, a grape variety which still exists today.

The two main designations were then “Champagne” located around Segonzac and “Borderies” to the north-west of Cognac.

Under the influence of ever-increasing demand, vineyards expanded on the left bank of the Charente. In 1603, Etienne Thevet, Surgeon of the Prince of Conti, celebrated the wines of Aunis and in 1629, in his “Theater of Agriculture”, Olivier de Serres placed these wines among the best white vintages.

Encouraged by the results obtained, the wine growers continued to plant vines, production became considerable and a real crisis resulted. The winegrowers tried to preserve their wines but they deteriorated. To remedy this state of affairs, some had the idea of distilling. It is therefore around 1600 that the transformation of wines into eaux-de-vie known as Cognac is attributed. This distillation process spread very quickly and some ten years later, foreigners bought brandy instead of wine.

After the cessation of wine exports abroad, the trade began to export new eaux-de-vie. These were cut on their arrival, at the rate of one part of brandy to 6 or 7 parts of water by the consumer, who had the impression of reconstituting the wine he drank previously. The slump as a result of the crises left stocks unsold. The customers then noticed that the brandy had improved with age and took a taste of “rassis” cognac. [rassis here could mean balanced instead of stale. I have seen the word rass used by the old colonial rum merchants.]

“La Folle Blanche”, a grape variety giving more finesse and more aroma to eaux-de-vie, then spread in the region. It was subsequently largely replaced by “Saint-Emilion des Charentes” or “Ugni Blanc” much less sensitive to gray rot.

Thus, the Charentes began to supply cognac to most foreign countries.

This export vocation is all the more remarkable, since it manifested itself at a time when the insecurity of the seas and internal disorders gave such an activity a particularly daring character.

Cognac before the Phylloxera crisis:

The brandy trade, while obeying regulations, appears to have been free in the 16th century. On the other hand, we know from precise documents that Henry IV conceded around 1600 to one of his relatives, the manufacture and trade of Cognac outside the kingdom as a real monopoly for the western provinces.

In 1712, a manuscript by Massé gives the following information: “It is not yet two years since the elders of the country assured me, which would postpone to 1622, which began in the said provinces, to transform wine into brandy.”

However, according to M. Vivier in his “Pays de Cognac” distillation would have started earlier than indicated in the manuscript of Massé; indeed, “The minutes of Notaire Lecourt note in 1529 purchase by a merchant of La Rochelle of four barrels full of good and marketable brandy at the price of 60 livres tournois for the four”.

More or less important houses then contributed to the creation of the market.

The reputation of Cognac gradually established itself and was already important by the middle of the reign of Louis XIV. Throughout this century, new houses were founded in the region.

From year to year the number of exports rose. Around 1730, foreigners were already buying 25,000 barrels. In the Encyclopedia of Diderot and d’Alembert published in 1751, Cognac is mentioned as a town in France “famous for its eaux-de-vie”. Later Cognac alone shipped more than 50,000 hectoliters (1) and exceeded 89,000 in 1792.

(1) Hectoliters of brandy and not hectoliters of pure alcohol.

However, subsequently, hard hit by the revolutionary wars and the Consulate, exports fell to 27,000 hectoliters in 1797, picked up significantly from 1805, reached the record figure of 99,000 in 1807, then as a result of the strict application of the continental blockade experienced a new crisis to fall in 1812, the year of the Russian campaign, to 16,652 hectoliters.

With peace, the market slowly regains its former importance.

Origin of bottling:

In the early years of the Juillet government, a retail merchant asked his usual supplier to ship Cognac to him not in barrels, as they had been doing for over two centuries, but in bottles and cases. “You are kidding,” the trader had cried, dumbfounded;talk to my neighbor who has just settled and will perhaps accept.” Thus a new method of presentation and sale was born. It was to quickly amplify the market (1).

(1) According to Martin Civat.

Exports which had not yet reached 53,000 hectoliters in 1820 —less than in 1789— exceeded 100,000 in 1830 to reach, with many fluctuations in between, more than 420,000 in 1866 and 478,000 in 1879.

The excellent years of production and the enormous reserves which resulted from it were to allow Cognac to triumph over the formidable but temporary crisis of phylloxera, the attack of which was particularly noticeable at that time.

In the face of disaster:

Phylloxera, an insect whose larvae killed French vines by attacking their roots, had been accidentally introduced from America during the importation of plants. From 1879, this insect led to the almost total destruction of Charentais vineyards.

The owners, faced with the heavy financial burdens created by the need to reconstitute their vineyards with expensive plants, intelligently exploited their grass resources and created the first butter cooperatives.

Reconstruction of the vineyard after the Phylloxera crisis.

Phylloxera attacked especially on vines planted in limestone and dry soil, favorable to its larvae. At the beginning, while living on aged stocks of brandy, the wine trade had to be satisfied with the productions spared in the strong grounds of the “Pays-Bas” or the sandy areas of the coast and the Islands.

Soon, the rebuilding of the vineyards was possible thanks to the grafting of French vines on American root stock which resisted the attacks of Phylloxera.

However, many problems arose and were solved only after repeated and expensive experiments. The difficulties of adapting American vines to French soils then prompted major research work either by the Ministry of Agriculture (Montpellier School) or by private stations (Cognac), either by owners themselves or by hybridizers.

Faced with the impossibility of replanting chalky Charentais soils, MM. Menudier and Verneuil, demanded and financed a study mission to America.

This mission was entrusted to Mr. P. Viala in 1887. This drew attention to possible employment of Vitis Berlandiéri. Due to the multiplication difficulties of this species, they then turned to the use of Berlandiéri hybrids which allowed creation of a whole range of artificial rootstocks for different terrains.

The Cognac District Viticulture Committee created the Wine Station with the main mission of experimenting with new rootstocks and determining which ones were best suited to each type of soil. The Station was directed by Ravaz from 1890 to 1896.

The important studies made thanks to the test vineyards of Parveau (Millardet. R. Lafon), Tout-Blanc (Couderc), Conteneuil (Verneuil), Marville (Ravaz, Guillon, Vidal), allowed reconstruction of various terrains. The latter was on the right track in 1898, both in Champagne and in the Borderies and the Bois, when the varieties of Pays-Bas resisted.

We can say that without the work mentioned above, the Charentais vineyards would no longer exist, except in a few small areas. Economic considerations may have subsequently made us forget the serious technical problems which arose, but economic questions only arise because the technical problems have been resolved beforehand.

In the end, while in Aunis, polyculture based on artificial meadows and milk production definitely replaced the vineyard, the latter was partially reconstructed, but much smaller than before 1875, in the Saintonge region, containing Champagne and Cognac. This reconstruction was carried out mainly on slopes not very sensitive to frost.

Folle Blanche, which had become susceptible to rot, following grafting, was partly replaced by “Saint-Emilion” (ugni blanc).

Commerce then had to redouble its activity following frequent usurpations in many countries, during the difficult period of the phylloxera crisis.

The current situation:

Since 1900, the area of the vineyard, out of an increase in recent years has not undergone very big changes; However. the volume of harvests varied in very large proportions under the influence of climatic conditions which vary greatly from one year to another (frost, coulure, etc.)

In 1954, the area of the vineyard was 65,830 ha, the total wine production of 3,373,372 hl. of which 1,775,297 hl. for the production of Cognac.

The quantity of Cognac exported during the 1954-1955 season corresponds to a value of more than 14 billion francs, which corresponds roughly to a third of total French exports of wines and spirits.

These exports have been increasing significantly every year for the past five years.

The phylloxera crisis coincided, unfortunately for our region, with the moment when almost everywhere we were now able to produce alcohols from grains or other origins. In addition, prohibition in the United States, various measures taken subsequently in many countries to reduce the consumption of spirits, as well as the consequences of wars, were all causes likely to reduce Cognac consumption.

More expensive than most spirits, Cognac can only hope to maintain its position in the market on a lasting basis thanks to its quality.

Nothing is in fact more difficult to maintain or increase than the market for a product that is not essential.

The brief review of the past, given above, shows the considerable fluctuations in sales and harvests over the centuries.

We can also see all the difficulties encountered.

In the midst of these difficulties, we will not fail to notice the dynamism of the traders, determined for example to conquer or reconquer markets after each war, that of the winegrowers, when it comes for example to reconstruct the vineyards destroyed by Phylloxera and the perseverance of distillers seeking to slowly improve the method of distillation, without giving in to the temptation of rapid and economical processes.

This dynamism and this effort towards progress, together with the respect of a slowly established tradition, constitute, in spite of difficulties which arise constantly, a rather good omen for the future.

Wines reserved for the production of Cognac

The non-volatile substances in wine, consisting of mineral salts, acids, tannoid substances and many other organic compounds (carbohydrates, nitrogenous substances, etc.), do not pass into the brandy.

Volatile substances, due to their low boiling point or being carried away by water and alcohol vapors, are found in large part in brandy and give it its fragrance.

In the perfume, we can distinguish the “fruit” which originates from elements existing on the grape or in it and the “bouquet” due to the products resulting from the fermentation.


The fruit is partly due to essential oils, moreover, poorly defined, located mainly in the skin of the grape and different from one grape variety to another.

Thus, according to Power, the smell of Labrusca is due to methyl anthranilate.

Hennig points out the Terpineol present in very small quantities in a Müller Turgeau wine, as well as Vanillin and Cinnamic Aldehyde.

Ordonneau isolated from a Folle Blanche brandy, terebene, a terpene boiling at 173°, very oxidizable, giving the product its truly winey taste. [This was at one point called “Cognac oil”.]

Cordonnier attributes the scent of Muscat to one or more unsaponifiable compounds of the terpene series, similar to Linalool, which exist in the must partly in the free state, partly in the combined state, probably in the form of heterosides. It appears to be formed on distillation in an acidic medium, probably by hydrolyzing heterosides. [Heteroside may be a french word that is equivalent to glycocide.]


The bouquet of eaux-de-vie results above all from the presence of fatty acid esters and substances which play a less important role: higher alcohols, aldehydes, acetals, volatile acids, etc. [I would argue that the bouquet results from radiant congeners casting their olfactory light upon esters.]

Higher alcohols:
Higher alcohols are formed during fermentation in varying amounts depending on the breed of yeast and also depending on the nature of the amino acids contained in the must, but from which they are not always derived.

These alcohols exist partly in the free state, partly in the form of esters.

Wines contain a little ethyl aldehyde which is an intermediate between sugar and alcohol and can also be formed by oxidation of alcohol.

Aldehydes show a certain affinity for alcohol with which they can enter into combination to form acetals, some of which have an odor reminiscent of flowers.

Pyromucic aldehyde or furfurol, with a pleasant odor, hardly exists in wine. It forms a little during the distillation.

Volatile Acids:
Acetic acid is normally found in all wines, but high doses are only encountered in “pricked” wines, this acid is then accompanied by large amounts of ethyl acetate.
These distilled wines give depreciated eaux-de-vie.

The other volatile acids appear in the composition of the wine only in very small quantities. They exist especially in the form of ethers resulting from combinations with alcohols. Among the main ones, mention may be made of caproic, oenanthylic, caprylic, pelargonic, capric and oenanthic acids.

They are considered to come from the disassimilation of yeast cells and are especially abundant in the lees.

Some others, like propionic and butyric acids, appear to be only products of accidental secondary fermentation.

Acetic acid in small quantities gives body to eaux-de-vie. Other volatile acids have an unpleasant odor.

Ether salts or esters:

Wine contains a fairly large number of esters. The role they play in the bouquet of wines has been exaggerated in the past and is currently quite debated. However, it is advisable to make a clear distinction between the ethyl esters of acetic, propionic, butyric, lactic, succinic, malic, tartaric, citric acids, in relatively abundant quantities in wines, but which do not participate in their bouquet and, of on the other hand, the neutral esters of the higher mono fatty acids esterified by ethyl alcohol or certain higher alcohols which pass into the brandy and give it a pleasant odor.

These esters are formed during fermentation inside the yeast cells themselves. Each breed of yeast has the property of forming more or less. Pure elliptical yeasts produce little. Torulas and apiculate yeasts form more. Pichia fermentans, Candida Krusei for example have the property of forming an abundance of ethyl and amyl esters.

Acetate ester or ethyl acetate is found above all in wines experiencing a beginning of ascension: more volatile than alcohol, it is part of the top products; it is responsible for the pricked smell.

Contrary to a fairly widespread opinion, no or only very few neutral esters are formed during the distillation; in fact the only neutral ester capable of forming in a substantial amount is ethyl acetate, the bad odor of which is known.

During distillation, only the neutral esters pass into the brandy. They distill only partially so that the eaux-de-vie contain less neutral esters than the wines from which they come. The fatty acid esters of the acetic series pass at the start of the distillation, while the esters of the ethyl lactate type pass at the end of the latter. [I think they may have been speaking at the limits of the days science…]

Wines distilled with their lees give eaux-de-vie richer in esters than wines deprived of their lees.

Certain other fermentation products such as diacetyl, acetoin, etc., have a slight influence on the smell of brandy.

Finally, one should note the presence, in spirits distilled in a simple still, of fatty substances which are, for example, esters of fatty acids and of glycerol.

Characteristics of Wines Reserved For the Production of Cognac:

The characteristics of a good distilling wine are in no way comparable to those required of direct consumption wines. The best distillation wines are in fact little appreciated for the table, because although they have a fine and delicate aroma:

—1) They have a strong and often unpleasant fixed acidity.

This acidity is essential to ensure a partial selection of yeasts and bacteria during fermentation and good preservation of the wine until distillation. It reduces the risks of secondary fermentation and thus partly replaces sulfur dioxide which cannot be used, due to its multiple drawbacks, which are:

—Realization of pure fermentations;
—Production of a large amount of aldehydes;
—Passage of sulfur dioxide in the distillate;
—Entrainment of a large quantity of copper during distillation;
Abnormal lowering of the pH of brandy by oxidation of sulfur dioxide with formation of sulfuric acid. Formation of foul-smelling compounds (mercaptans).

Acidity also plays a fairly important role during distillation because it leads to the hydrolysis of certain constituents of the wine with the release of odorous bodies belonging to the group of terpenes. [The acid helps release “Cognac oil”.]

—2) The alcoholic degree of good distilled wines is never very high. The resulting advantages are as follows:

—The musts which are not very rich in sugar give wines with low volatile acidity, what to look for;
—Wines with a low degree of alcohol make it possible to make a low degree of brouillis, which, as we will see later, constitutes an element of eaux-de-vie quality; [Broulis is the first product of the double distillation system. You want it at a low degree so your final product of the next distillation is not too high in ABV.]
—To make a determined quantity of brandy, you need a quantity higher in wine with a low alcohol content than in wine with a high degree of alcohol, resulting in a greater concentration of the perfume.

However, it cannot be said that the wines with the lowest degree give the best eaux-de-vie.

The following table shows that the quality of the brandy is mainly linked to the sanitary condition of the harvest.

The best eaux-de-vie are obtained with healthy harvests and wines whose degree is generally less than 10.5°.

The year which gave the best eau-de-vie during the last quarter of a century according to the opinion of the tasters is the year 1939 where the average of the degrees is 7.5°.

[Some interesting words in there with frost and rot… viticulture aint easy…]

—3) The best distilling wines are white wines, such as those from the Charentes which contain small doses of tannoid matter. Wine tannins indeed give a rather pronounced bitterness to the eaux-de-vie.

Charentes Wine Analysis Results

For documentary purposes, we can cite the following figures which are averages of analyzes carried out at the beginning of the century.

Averages of analyzes recently carried out at the Cognac Wine Station

Here are the averages obtained between 1900 and 1920.


—The average was 7.9°
—The minimum was 5.3° for a Saint-Emilion.
—The maximum was 10.9° for a Folle Blanche.

Total acidity:

—The average was 6 gr. 9. [I’m not sure of this notation. 6.9 grams?]
—The minimum was 3 gr.
8 for a Folle Blanche.
—The maximum was 11 gr. 9 for a Saint-Emilion.

The highest acidity figures have always been given by the wines of Saint-Emilion, which is the latest grape variety in the region.

Dry extract:

The general average, deducted from the remaining sugar is … 18 gr.
With a minimum of ……. …….. …….. …….. …….. …….. …….. …….. …….. 12 gr. 6
With a maximum of ……… …….. …….. …….. …….. …….. …….. …….. …….. 22 gr.

The dry extract is more important in wines from a harvest affected by gray rot.

Sugar remaining:

Small amounts of the remaining sugar were found in wines from Colombard. Often, however, this bottled wine undergoes a second fermentation which makes it sparkling and slightly sparkling.

Fixed acidity:

Charentes wines are characterized by a high content of fixed acids.

The following table gives the balance of organic acids for 5 wines harvested in 1938:

Balance of organic acids of Charentes white wines

Volatile acidity:

Due to the high acidity of the must, only a very low volatile acidity is produced during fermentation. Only wines from grapes affected by gray rot have a high volatile acidity.

Healthy wine ……. ……… 0 gr. 25
Wine from a harvest affected by rotting ……..
1 gr. [For a comparison, rum ferments featuring vinegar may start at 3.0 g/L of VA] 

Reducing substances:

The grape is reducing and contains Ascorbic Acid, the quantity of which decreases during ripening.

As soon as the Ascorbic Acid is completely oxidized, the must takes on a yellow-brown tint due to the oxidation of the phenolic compounds.

To avoid overoxidation of the must and partly irreversible oxidations, the grapes should be collected before the reducing power of the Ascorbic Acid disappears and the must should be prepared by avoiding excessive aeration and too much contact with iron.

The bromine number, which provides information on the content of phenolic compounds, increases notably in hydraulic press juices.

In summary:

Good distilling wines must be straight in taste and sufficiently acidic to ferment properly and keep until distillation without the aid of sulfur dioxide.

The various organic acids and ethers give them particular aptitudes for producing fine eaux-de-vie.

When the grapes do not undergo too much over-ripening, the elements of the bouquet, protected by reducing substances, do not undergo the destructive action of oxidation. The eaux-de-vie obtained are then very fragrant.

Elements of the quality of Cognac Eaux-de-Vie

Charentaise eaux-de-vie are not of equal quality. Those produced in the Center of the Region are superior to those coming from near the ocean or the confines of Limousin and between these extremes, there are a large number of intermediaries.

While each estate can produce a special brandy, its distinctive characteristics are generally not sufficiently marked to need to be taken into account.

The owners and the merchants divided the region into crus.

The map was established according to the quality of the eaux-de-vie and the nature of the soil.

Faced with these divisions one can wonder what are the essential factors of quality.

We will distinguish the following:

The grape variety:

The grape variety, as in all crus, plays an important role. Indeed, if we distill a wine from Muscat, highly esteemed for the table, we obtain an eau-de-vie that is closer to the scent of cologne than to fine Charentais products! It is the same for all wines with special aromas which must be rejected.

If we distill a wine that does not have a special aroma, but comes from a grape variety that matures very early, we obtain a dull and pomaded eau-de-vie. [I’m interpretting pomaded as perfumed but still dull.]

It is difficult to predict the quality of eau-de-vie based on that of wine, because the qualities of wines are mainly attributable to fixed substances, while those of eaux-de-vie come from volatile substances, which while in small quantities in the wine, become concentrated during the distillation.

Experience has shown that, for the still, wines that are a little acidic, with a rather low alcoholic content, straight in taste, with a fine bouquet without being exaggerated, should be sought for the distiller.

The grape varieties which can be used must mature rather late. Indeed, when maturity takes place very early, the elements of the bouquet are largely destroyed by oxidation.

The grape varieties giving the best eaux-de-vie in Charente are “Folle Blanche” and “Saint-Emilion”.

Due to its resistance to gray rot attacks, which allows harvesting for a fairly long period without altering the grapes, and the regularity of the quality of the eaux-de-vie that can be obtained from it, Saint-Emilion has largely replaced the Folle Blanche.

Jurançon gives slightly less fine eaux-de-vie.

Tests carried out with recent hybrids in which the grapes harvested at full maturity have given poor results (“pomaded” eaux-de-vie).

On the other hand, some crossbreeds (crosses of Vinifera varieties) give good eaux-de-vie. However, a test is necessary for each of them, because the viniferous grape varieties are not homozygous and recessive characters may appear during crosses.

Mr. J.-L. Vidal has obtained several interesting half-breeds, likely to replace, soon, the endangered Folle blanche and the Colombard.

The soil:

The terrain has an indisputable influence. The eaux-de-vie from siliceous soils bear little resemblance to those from limestone soils.

Tasters from the main trading houses are not mistaken about the homeland of the eaux-de-vie that is presented to them and as the value is based on the quality and that this is largely subordinate to the nature of the soil, it follows that variable prices are established according to the places of origin. [#terroir]

The influence of the soil is felt first of all by its physical structure: the crumbly limestones which ensure regular nourishment and progressive maturity give a high quality.

On the other hand, depending on the nature of the soils above which they have ripened, the grapes are accompanied by different yeast species. However, during fermentation, these yeasts develop substances that give the various wines their own character.

The composition of the flora of the yeasts resembles that of the meadows, it varies according to the nature of the soil from which it originates.

On this subject, it is possible to think that the elements which contribute to the elaboration of fine eaux-de-vie are not very different from those which distinguish good Charentes butters.

From a geological point of view the Upper Jurassic is found everywhere, from England where it is typical to Asia. However, in Charente, it offers a particular expression.

With regard to the Supra-Cretaceous, it appears in Charente in such a characteristic form that in the international nomenclature, these lands are designated by Charentais names: Angoumien (d’Angoulême), Conacien (de Cognac), Santonien (de Saintes).

These latter formations are remarkable for their richness in lime carbonate and for the fact that the eaux-de-vie they provide are the best and the most renowned.

Limestone subsoil [Missing picture of cross section of limestone soil.]

The texture of the rock, apart from its origin, is of paramount importance. It is thus that the beautiful eaux-de-vie of Grande and Petite Champagne only come from the Supra-Cretaceous period, while the Borderies, which enjoy great esteem, come from decalcification sites to the north-west of Cognac, whose soil is free of Calcium, but whose subsoil is limestone.

In general, there is a fairly clear relationship between the quality of eaux-de-vie and the active limestone content of the subsoil.

The climate

The influence of climate is too little known not to be mentioned.

The Charentes climate is temperate and humid, hot enough to be able to ripen the grapes properly, but not scorching. The bunches ripen under the action of moderate sun and this is an important point.

Everyone knows that fruits or flowers have a flavor or a fragrance that is all the more delicate the more they have been able to develop in a less overheated atmosphere. The same flowers, the same fruits harvested in hot countries have neither the same value nor the same delicacy.

Where are the really aromatic wines, for example, and do they have a finer and less heady scent? It is neither in Spain, nor in Algeria. It is in the mistier, colder regions of the Gironde, Anjou, Champagne, etc… It is that light and heat have an extremely intense action on most organic compounds in fruits and flowers. They destroy the acids, oxidize the hydrocarbon substances which constitute the bouquet of the fruit, transform them into resins, etc…, more oxygenated bodies and with a pungent and less pleasant odor.

Hilltop vineyards in the Charentes [Missing photo of a vineyard.]

This also explains why the eaux-de-vie from the hottest years have less finesse and mellowness, are drier and inferior to the eaux-de-vie from cooler years.

The climate of the Charentais basin is influenced by the latitude: the proximity of the sea, the vicinity of the hills of Périgord, Limousin and Gâtine, as well as by the corridor of the Strait of Poitevin. It is part of the Aquitaine climate, quite particular, because it is subject to two opposite influences: the Armorican climate and the Continental climate. In the Charentes, the influence of the Continental climate is more marked than in the rest of the Aquitaine Basin.

In fact, the vegetation there is very special. It is a crossroads province where the 4 flora of Europe meet and become entangled.

The Iberian flora is represented there by the Tauzin oak. Mediterranean flora is abundant there; the part played by the Green oak in the Angoumois and Saintonge sites is striking. The Atlantic flora invades it with its maritime pines, its eagle ferns, its broom and its heather as soon as the soil favors them. Finally, the mid-European flora forms the very basis of the Charentaise vegetation.

The nature of the soil does not act alone on the quality, because the succession of vintages, that is to say the influence of the terroirs on the quality of the eaux-de-vie, does not extend from the North-East to the South-West in a series of bands formed exclusively by the outcrops. The proximity of the sea to the prevailing winds (West-North-West), gives the climate, in certain places, an influence as strong as that of the land.

Around the sea, even the calcareous grounds give less esteemed products and the vineyards, instead of following the direction of the outcrop lands, become parallel to the shores of the Atlantic, close to it.

To the east of the Charentais Basin, on the other hand, altitude of the land determines more violent condensations in a colder zone and makes the distribution of the vintages dependent on the disposition of the last slopes of the Massif Central.

Some digital data relating to the climate.

a) Temperature:

The department of Charente is crossed by the + 20° isotherm. This high temperature is due to the hot currents which blow from the southwest.

The annual average temperature is 13.5°.
The average winter temperature is + 6.5°.
The average summer temperature is + 21.7°.

b) Rainfall:

The average annual rainfall in the Cognac region is around 800 mm. The number of rainy days fluctuates around 130 days,

There are two rainy seasons, one extending from October to January and the other from May to June.

The importance of the rains increases when you get closer to the Massif Central


Have a negative influence on the quality of eaux-de-vie:

—Late sulfurization, in particular the use of wettable sulfur very adherent, after blooming;
—Presence of rot in the harvest;
Casse brune as well as the maderization of the wine;
—Too prolonged storage of the wine on its lees;
—Use of sulfur dioxide;
—Presence of seeds in the wine, especially if they are crushed;
—Presence of torn roundups;
—Storage of wines en vidange; [vidange here may mean containers that are either not full or possibly that previously held something but were not cleaned.]
—The use of pulverizers;
—The use of continuous presses (prohibited);
—Too violent pressing;
—Oil leaks in the oil cups; [Old cups holding the oil to lubricate equipment.]
—Poorly lined cement vats.

From the beginning of the 18th century, an idea of the hierarchy of terroirs took shape. This division into crus was gradually defined by the continuous effort of wine growers and merchants towards the selection of eaux-de-vie by quality. During the 19th century, the boom in the Cognac eaux-de-vie trade gave rise to ever deeper knowledge of the classification of terroirs and gave rise to a geographical division, based solely on the quality of the eaux-de-vie, which served as a fixed basis for pricing.

The decree of May 1, 1909 officially established the boundaries. These boundaries were taken up and clarified by the decree of January 13, 1938. The sub-regional appellations are as follows:

—LA GRANDE CHAMPAGNE includes whitish lands surmounting the crumbly limestone layers of the Supra-Cretaceous (Coniacien, Saintonien, Campanien) which are freed to the highest degree from maritime influences on one side and continental on the other. In this cru, the soils and subsoils have a high content of active limestone and the rainfall is the lowest of the two departments. It is this cru that provides the finest, most delicate, cleanest eaux-de-vie, those which improve the most with age. On the slopes of this region, the vine does not fear hot, bare soils where the rock is often flush with the ground and the green oak barely sinks its gnarled roots.

—LES PETITES CHAMPAGNES have more or less the same characters and come from identical terrains, closer, however, to the sea or the interior; the brandy that comes from it has not grown to the same degree, qualities that distinguish Grande Champagne. However, it sometimes comes in a bottle with the latter under the name of “Fine Champagne”.[Fine Champagne is the label term for a mix of cognac from Petite & Grande Champagne. Remy Martin is the principal user of the term. -Andy Garrison]

On the slopes of the Petite Champagne d’Archiac, vines cover the chalky ground, where only poor and thick grass grows.

—LES BORDERIES include a Cretaceous (Saintonien-Conacien) zone physically and chemically decalcified during the formation of the Charente valley in the middle of the Tertiary period. The ground is covered in many places with heather moors. The decalcification was not, however, complete. This explains certain disparate plant associations such as those of walnut and chestnut. This perhaps also explains the originality of the Borderies de Cognac brandy. The eaux-de-vie that come from this very small area are in fact sought after for their particular charm, their softness, their bouquet and also for their ability to age quickly. The presence of a significant proportion of Colombard in the grape variety does not seem totally foreign to these characteristics.

LES FINS BOIS include Jurassic and Cretaceous terrain with a subsoil made up of hard limestone, which is not yet too directly influenced by the proximity of the Ocean and the Gironde, nor the altitudes which encircle the Charentais basin. The eaux-de-vie which come from it are less fine than the Grandes and Petites Champagnes, but they age faster. [It is so fascinating to ponder what volatile properties we can measure which would contribute to the notion they can mature faster. Lots of mystery. You cannot doubt these authors must have incredible experience.]

The Fins Bois include the reddish “terres de groie” and the “Pays-Bas”. [Pays-Bas may best be low-lands and not outer-lands.]

—LES BON BOIS include all the Cretaceous, Jurassic or Tertiary lands, poorer in limestone, whose limestone is harder, more exposed to the influences of the maritime climate and altitude of which we have spoken. In the South, between the maritime pine woods and the broom and heather moor, the vines have also become acclimatized, but provide a leaner and less fine Cognac.

Distillation made with particular care, eliminating most of the lees and producing a brandy of high degree often allows very correct products to be obtained.

LES BOIS ORDINAIRES and LES BOIS A TERROIR include the different lands of the coast or the Islands, where the influence of the maritime climate is felt. The spirits that come from it often have a taste of terroir, which can be mitigated or even removed by taking special precautions for distillation.

In reality, to be fair and precise, such a delimitation should be carried out for each vineyard (parcel delimitation), because the tasters point out that within each cru, there are restricted areas whose eaux-de-vie are better or worse than the whole cru and which should therefore be classified in a different cru.

The Charentais still

If the quality of a brandy depends on the nature of the wine used and the skill of the distiller, it also depends on the still used. This is why we will carefully examine the different parts of it and the conditions which must govern its execution and its assembly.


Main element of the Charentais apparatus, the copper boiler of generally simple construction must fulfill two essential conditions.

1 ° It must allow complete and easy cleaning of all its parts.
2 ° It must ensure the wine a great regularity of heating.

“Straight” or “onion” shaped boilers are built. The straight shape has two almost right angles at the bottom and at the top, which makes cleaning quite difficult. This drawback is mitigated in the case of an “onion” shape having only a fairly open angle at the lower part.

Whatever the shape, all parts of the device must be carefully “planed”). The leveling or hammering which consists in tightening the pores of copper to give it more resistance is to copper what quenching is to steel. A well “planed” boiler has a smooth interior surface to which the lees do not adhere: cleaning is thus easier.

The bottom of a boiler is in direct and continuous contact with the flame and when its thickness is too small, the adjustment of the fire becomes difficult, especially at the beginning of the “heating”. This results in inconveniences: irregular boiling, shots during the “bonne chauffee”. When the bottom is thick, these disadvantages are reduced: the shots are damped, the bottom playing the role of heat regulator. [This is interesting to contemplate because “shots” can be bumping from a lack of imperfections to seed a boil. I saw wild bumping with the birectifier before adding pumice stones to the boil and have heard of others experiencing it with larger stills. ]

For boilers with a capacity of less than 5 hectoliters, the minimum thickness is 5 millimeters. Above 5 hectoliters the base must have at least a thickness of 1 millimeter per hectolitre of capacity up to 10 hectos. Above 10 hectos a thickness of 10 to 12 millimeters seems sufficient. It should be slightly convex: two to three centimeters at most, so that none of its parts remains uncovered for too long when the boiler is emptied. [Fascinating data points!]

When the lower part of the boiler turns downwards, this is proof of its insufficient thickness. In this case, its replacement must be carried out immediately. Indeed, as the boiler no longer empties completely, if it was continued to be used under these conditions, it would give the brandy a very pronounced cooked taste.

When a distiller orders a boiler, they must clearly specify the thickness to be given to the bottom. To check this thickness, thye should not refer to the measurement of the outer edge of the bottom when the boiler is finished, but have them supply the part that the boilermaker removes to place the drain pipe. [Never be fooled again!]

The Capital [I translated chapiteau as capital, but Andy Garrison suggested leaving this untranslated or better as hat, cap, or helmet. I was pretty selective with untranslatd words, but I bet you’d have an opinion if you looked at one on your still every day!]

Placed above the boiler, the capital is either pear-shaped surmounted by a Swan Neck, or in the shape of a Moor’s head with a right arm slightly inclined on the coil.

In Grande and Petite Champagne, where the distiller must seek to collect all the essences and bouquets of the wine, it is preferable to use capitals with Moorish heads or very low Swan necks, because they allow the substances which contribute to the eaux-de-vie of these wines their special cachet as complete as possible. However, in this case, it is essential to regulate the fire carefully and not to overfill the boiler, in order to avoid excessive entrainment by the steam. [Cognac is so refined they match still heads to specific quality ferments!]

The high Gooseneck capitals cause a partial rectification of the brandy. They are particularly suitable for terroir crus, because they reduce entrainment by alcoholic vapors of the essences particular to these wines. Vapors of these low volatility essences then condense on the very walls of the Gooseneck and flow back into the boiler. [Basically they distill at a slightly higher ABV because the shape provides subtle reflux. Some of this “terroir” may be tufo aroma from the break down of lees. Particular lactic acid character could also be a play. There is lots to speculate on.]

In all cases, it is useful to install very high “chapeaux”. The bottom of the “chapeau” thus removed from the surface of the wine, is then less stained by projections of foam or lees during heating; the result is a favorable effect on the quality of the eau-de-vie: no “cooked tastes” or “grilled odors”. [This is fascinating. You want the top to see only vapor and no projections where lees may bake on create the tufo aroma. A producer may trouble shoot this with the birectifier where some of this aroma would appear in the very last fractions. It would be remedied by either filling the still less or removing a percentage of the lees.]

The capital is nowadays assembled to the boiler by two mid-circles provided with male and female grooves with special rope joints, all tightened by bronze bolts. In the past, the joint was made by ash, which was much less practical. [I have not heard of ash which I think is translated correctly but rather “luting” which bakes on when the still is heated to provide the seal. I wonder if the grooved joints are lapped flat and can make with no distortion when tightened.]

[Missing simple diagram of the Chartentes still with pre-heater.]

The Wine Pre-Heater

Placed after the capital, the “wine pre-heater” constitutes a heat recovery device. It saves time, fuel and cooling water.

This device makes it possible to raise the temperature of the wine before loading the boiler. For that a pipe coming from the capital crosses it and ends at the coil. This pipe must pass very low in the wine heater. because if it is placed too high, there is a risk of boiling the surface of the wine before heating the bottom. It is preferable that this pipe does not form an entire turn because the heating is then too strong.

The old models did not have a three-way valve allowing the alcoholic vapors to pass, either through the wine heater or directly into the coil through a pipe bypassing it.

This improvement makes it possible to start heating the wine just at the desired moment, so that it is not brought to too high a temperature when the boiler is loaded.

A safety pipe placed above the wine pre-heater crosses the pipe and emerges near the outlet of the coil. If the heated liquid boils, the vapors condenses in the “pipe” and exits at the bottom of the pipe, thus warning the distiller that they have overheated the liquid and that they must immediately change the direction of the vapors via the three-way valve. It would be better to have a thermometer indicating the temperature of the wine. A level tube and an overflow valve indicate the volume of liquid to be introduced. The boiler and the wine heater have been calibrated to the same capacity.

If the pre-heater monitoring cannot be sufficient, it is good to only use this device for wine. Indeed, any liquid put in the wine heater (especially brouillis) must not come to a boil, otherwise it could have an unfavorable influence on the brandy. [Basically you can use this for the first stage of distillation with wine, but not for the second stage when you would be pre-heating brouillis. It would be good if they could articulate the negative effect because I can only imagine distillers being tricked by the brouillis heating much faster than wine. Andy suggested their was a high incidence of losing alchol to vapor.]

The Serpentine:

The pipes forming the turns of the upper part of the coil are of a substantially larger diameter than those of the lower part. With large diameter pipes the condensing surface is larger. However, if the diameter is too large the boiler may puff. [puff came from “souffler”, but that could be pant or whiff or quite a few things and I am trying to follow the logic of what may physically happen. I have seen inconsistent sputtering of output from condensors and maybe that is the phenomenon. Andy Garrison calls it chuffing or huffing and has observed it on condensors that are improperly sized.]

For a 10 hectare boiler, the coil must have a length of at least 26 meters. [Wow, that is long!]

All soldering should be done with pure tin and not with lead (or better yet brazed).

The liquid flowing at the outlet of the coil must have a regular flow. An irregular flow can be caused by an irregular slope of the turns (7 to 10 in number) or a base which is not horizontal. The maximum slope of the turns must be 35 millimeters per meter.

Irregular flow can also be caused by:
a coil of too large diameter;

by a too thin bottom of the boiler;
by too cold water at the top of the pipe; [pipe here is probably the serpentin tub.]

With some devices, despite a renewal of the cooling water, the liquid leaving the coil always has a higher temperature than the water placed at the same level in the “pipe”. It comes from: [pipe here is propably again the serpentin tub.]
—Insufficient length of the coil.
—Too steep slope of the turns.

In both cases, the liquid arrives at the lower orifice without having had time to cool down.

The coil is placed in a basin or “pipe” containing the cooling water.

“The Pipe” usually placed inside the room where the distillation takes place can advantageously be placed outside. We then have the following advantages: [pipe here is propably again the serpentin tub.]
—Easier cooling.
—Total elimination of water vapor.
—Very noticeable space saving.

Brouillis tanks:

Many distillers collect the brouillis in tanks. In recent years, we have become accustomed to having cement tanks built. The artificial cement which releases lime at the time of setting is attackable by acids and therefore by brouillis. It is useful in this case to make an interior line in molten cement, more resistant than artificial cement. [I think this quickly evolved to glass lined concrete and then likely stainless steel.]

The ideal would be to make an interior coating of welded plates of certain hard plastics free of plasticizers. These coatings are unfortunately expensive.

[I’m ommitting two pictures that show different variations of the capitals.]

Cooling slabs:  [Dalles de refroidissement:]

The temperature of the water in the pipe rises rapidly during distillation. To ensure vapor condensation, it must be cooled or renewed.

When there is a large quantity of water there is no difficulty; on the other hand, when the water is not yet very abundant, it is necessary to install cooling slabs.

Significant cooling is obtained with 16 meters of “slabs” per boiler. These should be long and shallow. The return of these slabs must be done by large diameter pipes to the lower third or quarter of the pipe.

When the outside temperature is high, the tiles cannot provide cooling on their own and cold water must be introduced into the bottom of the pipe. This must be brought there slowly by a pipe fitted with an air jet.

Whenever possible, instead of intermittently refreshing, it will be preferable to supply the pipe with a small continuous current of cold water. [pipe here is propably again the serpentin tub.]

A practical device for the distiller to realize the quantity of water they use, consists in placing a funnel near the pipe, the end of which opens out at the base thereof. The cold water inlet hose ends with a tap, placed above the funnel, which allows the amount of water to be used to be adjusted.

For the condensation of alcoholic vapors to be complete in normal distillation, the temperature of the liquid collected in the alcoholmeter holder must not be greater than 25 ° centigrade or better still 20 °. Above this temperature, all the vapors are not condensed and there are notable losses. [I remember Arroyo quoting 20° as his preference.]

Furnace assembly:

The furnace must be mounted in such a way that the flame never reaches the level of the liquid when the heating is finished, that is to say when the alcohol is completely extracted. In the past, most boilers were placed on stoves which allowed heating only from the bottom.

In other systems, the flame was conducted around the boiler by a circular fire tower, placed very low.

With these different systems it was only accidentally that we observed tastes of “cooked”, “pot” or “riméd”. Currently many stills heat with coal; and, to make better use of its heat, builders have increased the heating surface by placing fire towers sometimes up to half the height of the boiler. [I took Andy’s advice and did not translate”rimé”. It will pop up later with a better explanation.]

The manufacturers of these furnaces have aimed at fuel savings—which can actually reach 10 to 15%—without asking whether their device would not be detrimental to the quality of the eaux-de-vie. With fire towers placed too high, the copper is heated “bare” before the end of the “heating”. The parts of the liquid which are in contact with the metal thus heated to naked are “roasted” and give the whole brandy bitterness and a “pot”, “riméd” taste which in some cases reduces their quality to the point of making them unusable. This special taste is indeed very persistent. [Rimé is like a ring of cooked grime…]

To determine exactly the height at which the flame can, without inconvenience, be in contact with the walls of the boiler, here is how we proceed:

From a 5 hl boiler “load”, filled with “brouillis” at 30°, we collected 145 liters of “heads” and “hearts”, 184 liters of “seconds” and “tails”, or in all: 145 plus 184 = 329. There remained in the boiler 500 – 329 = 171 liters of “marc”. (In general, after proper heating, there remains in the boiler a quantity of liquid equal to one third of its capacity at “load”). 171 liters of “marc” rose in the boiler to a height of o m. 18 (fig. Above).

[### very interestin figures here and I have not seen the marc term used in this context. You can see in the figure that as the liquid level decreases, the flame would also have to be decreased.]

So that a boiler of this capacity can never heat “bare”, it is necessary that the upper limit of the surface of the heater, whatever the mounting system used, does not exceed 10 to 12 centimeters (in the case of of 5 hectos) above the bottom level, as indicated by the dotted line (ab) in the figure above.

[I omitted a few photos of Cognac stills. Nothing special.]

In general, it is necessary to require of the company which does the assembly, that the upper part of the fire towers —when this system is chosen—is placed 6 to 8 centimeters below the level of liquid remaining in the boiler when the heating is finished and the part between (a and c) is well closed with refractory earth, so as to prevent the flame from penetrating between the bricks and the body of the boiler. These are the two essential points of the assembly that it is very easy and very useful for the winegrower to control. It is essential that the drain pipe is completely and solidly embedded in the brickwork so as to avoid contact with flames which would “rhyme” in this part.

Reverse furnace boilers:

Some boilers have been installed recently by reversing the furnace (see photo). This arrangement makes it possible to keep the entire installation in a perfect state of cleanliness. [I’ve omitted some photos but they don’t make this distinction clear to me.]

Watertight door boilers:

Interesting modifications were made to the boiler doors by a local builder.

The doors are sealed with asbestos padding.

Airtight doors with asbestos gaskets avoid an always awkward air intake at the doors and many distillers have the habit of wedging a piece of wood behind the latch of their door to avoid this air intake which activates the hearth and which makes more delicate the conduct of a good heating where it is necessary to have precisely a soft and constant heat, hence a greatly improved operating flexibility of the boiler. What’s more, these doors, which are basically double doors, avoid significant heat loss and make it possible to achieve significant savings in coal. The draft is provided by a rule placed on the ashtray door, resulting in better distribution of the air under all the grid and the elimination of shots fired at the boiler. What’s more, this draft system allowing more complete combustion of the coal while consequently achieving fuel economy must reduce the quantity of clinker and ash, hence less frequent ash removal. [I think the shots here are super heated flare ups inherent to this chaotic system.]

The second originality of the system lies in the installation of oscillating grates in two parts which allow with a simple lever to descend the grates with all doors closed, this in order to avoid, always in the same spirit, the air intakes which do not fail to occur each time that one opens the doors to give a shot of energy. This system of oscillating grids also has the advantage of forming the clinker (which it is not possible to avoid) either glued on the grids as in the old hearths but above the grids which does not interfere with not the draw from the ashtray doors. [energy was my choice from “ringard”. I’m also not sure about clinker which comes from machefer which I imagine is a type of waste slag that builds up.]

In summary, this system allows a saving of coal resulting from several factors: insulating doors, elimination of the air intake at the level of the doors and consequently more complete and more controlled combustion of the coal. In addition, an original de-ashing system avoiding the use of ringard while facilitating the conduct of the distillation. [#SOS page 54, again I could not really figure out how to translate ringard.]

From the tests which have been carried out, it emerges a significant saving in fuel and a significant reduction in ash and machefer. [I want to translate machefer as slag, but maybe someone has a better english word.]

In Summary

The Boiler…

All the parts that compose it must be very well “planed”.
The bottom of the boiler must be of a thickness appropriate to its capacity. From eight hectoliters a bottom of one centimeter is necessary.

The Capital…

In the best vintages where the distiller must seek to collect all the essences and bouquets of the wine, capitals with “Moorish heads” or low swan necks are used, because they allow as complete entrainment as possible, materials that contribute to giving the eaux-de-vie of these “crus”, their special cache, their superiority.

The wine pre-heater…

This device saves time, fuel and cooling water.
It can be fitted with a 3-way tap and can only be used for wine.
Its cleaning and interior maintenance must be as frequent as for the boiler.

Pipe and Coil… [pipe here is propably again the serpentin tub.]

The basin or “pipe” in which the coil is placed must have a sufficient capacity so that the water which ensures the condensation of the vapors does not heat up too quickly. The length of the coil and its diameter must be appropriate for the capacity of the boiler.

Boiler Assembly…

In the so-called “fire tower” mounting system, it is necessary to require that the upper part of the “fire towers” be placed 6 to 8 centimeters below the level of the liquid when the alcohol is completely extracted.

It is essential that the drain pipe is completely and solidly embedded in the brickwork so as to avoid contact with flames, which would “rhyme” in this part. [“rimer” being hard to translate but implying a site for scorching and creation of off aroma.]

How the Charentais still works

Discontinuous distillation with successive repassing.

“Cognac, king of our alcohols whose reputation is worldwide, to such an extent that its name has been usurped, has since ancestral times been produced by a two-step method.”  -Ch. MARILLER. [Mariller was famed agro chemist who contributed to a lot of books and even advised Kervegant on writing Rhum and Cane Eau-de-vie. I translated an excerpt of his writing on absinthe.]

Conduct of distillation in the Charentes is carried out as follows: wine with its lees in suspension is introduced into the boiler with the capital closed. Moderate heat of the hearth brings the liquid to a boil, alcoholic and other vapors are given off, condensed in the condenser, and flow through a test tube and thence into a barrel or other container.

We stop when the alcoholmeter indicates 0 degree. The liquid flowing between 5 and 0 degrees is called “tail”. It takes about 8 hours for this heating process: we thus obtain the “brouillis” titrating from 24 to 32° depending on the degree of wine used. [What is unique here is that they take it to zero, indicating that they are finding and chasing high value aroma.]

After having emptied the boiler, the same distillation is repeated twice with new wines. After the third heating, enough “brouillis” is obtained to proceed with the “bonne chauffe”.[So we see bonne chauffe is the term reserved for the distillation of the brouillis.]

The “brouillis” which read around 26° are then placed in the boiler and distilled. The first portions of the distillate, called heads, are colored or milky. Depending on the year, 1 to 2% of these top products are eliminated, which are recycled with another brouillis or with wine. [The milkiness comes from not from the most volatile components but from the initial distillate rinsing out components clinging to the condenser. Some distillers conduct a “demisting test” and heads are only collected so long as the product when diluted is milky.]

The clear spirit or “heart” which flows up to 60° or 58° is then collected.

What then passes to 0 degree is set apart, it is the “second”. The time chosen to separate the “second” from the “heart” is the “coupe”. [coupe sort of translates to drastic cut or cross section. It does not really translate to “cup”.]

Distillation carried out under these conditions is much more entrainment by steam than a separation of the volatile elements according to their boiling point, this is what gives Charentaise disitllation its character.

[This is a prett key admission and relates to what we see in fraction 5 of the birectier and what Arroyo called tail waters. It also relates to the functioning of the three chamber still which sees constant flavoured steam entraining high value aroma, but only if the distilling material has the potential.]

Comparison with other distillation methods:

The distillation of the wines can be carried out by methods which differ appreciably from the Charentais process, they are:
—Batch distillation without repassing (so-called first-draft devices).
—Continuous distillation: Adam’s apparatus with column plates.
—Vacuum distillation.

These rapid and economical methods made short appearances in Charente at various times.

The products obtained have never been able to compare from a quality point of view with Cognac obtained by the Charentaise method.

Continuous devices prove to be much inferior to alembics in carrying out fractionation of impurities. If rectification is weak, the impurities which, by their nauseating or acrid odor and by their unpleasant taste, depreciate the brandy are collected at the same time as the desired perfumes. When we want, by means of a more thorough purification to completely eliminate the undesirable products, we lose at the same time part of the bouquets and aromas which contributes quality to the brandy. On the other hand, since the wine stays only for a short time in the column (10 to 15 minutes instead of several hours in the still), extraction of essential oils and high boiling esters contained in the lees which contribute powerfully to the formation of the natural bouquet is poorly carried out. [There is a lot of overlap in aroma so if you distill at too high an ABV you will compress all the faults into the high value aroma and it will be all or none. And at the same time, Cognac requires or even justifies time under heat.]

Finally, continuous distillation has less flexibility than intermittent distillation. As in the case of the latter, one cannot vary the quality of the eau-de-vie by modifying the speed of the distillation, the proportions of top and bottom products, etc. [Speed of distillation is a key variable and slower distillation runs are either justified or not. Garbage in garbage out is the rule of the day. The birectifier is a great tool to examine if your ferment justifies slower distillation.]

In the Charentaise distillation there is mechanical entrainment of fatty substances. [Basically, lots of steam distillation with very little ethanol.]

Partial vacuum distillation has the disadvantage of greatly reducing the proportion of aromatic principles contained in the distillate, and consequently of giving short eaux-de-vie, taking on only little improvement with aging. [Vacuum distillation is the kiss of death…]

Brandy analyzes from the same wine

In an investigation into the influence of distillation methods on the composition of brandies, Dr. James Guymon, of the University of California, after having made a detailed study of the continuous distillation process with plates and of the Charentais process writes the following sentences: [Professor Guymon is referenced all over the blog! You can take an entire 1970’s distillation course with him.]

“Despite the technical and other objections that can be formulated against the “double distillation” processes when a continuous method can be used, it is nonetheless true that the still is used to the exclusion of any other distillation process in certain brandy-producing regions and in particular in France.”

“It is unlikely that the exclusive use of the still would have continued for so long if it did not contribute to the quality of the products. It is certain that this quality gives rise to many imitations.

Ch. Mariller. Distillery professor at the National School of Agricultural Industries writes: “To maintain our reputation, we must above all maintain manufacturing techniques. The attempts made to carry out distillations with concentration via continuous columns have produced disastrous results from this point of view.

Conclusion :

The long and expensive Charentaise distillation method, implemented by a good distiller, produces products of a higher quality than that of eaux-de-vie obtained by other methods.

Passage of Volatile Substances during Distillation

The volatile substances of the wine other than alcohol, constitute elements of the bouquet. Contrary to a fairly widespread opinion, mixed liquids do not distill in order of volatility; in fact the distillation is not carried out according to the vapor pressures, but according to those which result from the reciprocal solubility of the various products.

It is useful for the distiller to know the moment of passage of a given taste or such odor, in particular of the “second” taste, because it is this which conditions the cut to be made.

Tasting is the best way to determine whether to cut early or remove a lot of heads; however, knowing the crossing points of the different good or bad odorous bodies allows us to understand the functioning of the Charentais still and to use it as best as possible.

Samples were taken at 5 to 5 degrees during “brouillis” as well as during “bon chauffe”. (1). Analysis of these samples made it possible to draw the curves which show the passage of distillate components as a function of the degree of the latter. We have operated on several different boilers (2). However, the curves for each element were substantially parallel, which suggests that the pace of the distillation is identical.

(1) These samples were taken from MM. H. COUILLAUD, in Clion (Fins Bois);
DESCLAUD, manager, property of MM. HENNESSY, in Beauvais-s/Matha (Fins Bois);
R. GOUJON, crop manager of Mrs. P. CASTILLON DU PERRON, in Touzac
(Grande Champagne);
R. GRENIER, manager of the property of Mr. Maurice HENNESSY, in Javrezac (Borderies);
We would like to thank MM. the Distillers for their precious collaboration.

(2) The assays were carried out by the following methods:
a) Volatile acids expressed in Acetic Acid titrimetrically measured in the presence of phenol red.
b) Neutral esters expressed as ethyl acetate measured by alkaline saponilication.
c) Aldehydes expressed as ethanol assayed by the JAULMES-ESPEZEL method, modified for alcohols.
d) Furfurol in pyromucic aldehyde, determined by colorimetry in the presence of acetic aniline.
e) Higher alcohols, expressed as isobutyl alcohol and colorimetrically dosed by comparison with an arbitrary standard according to the official French method of modified fraud.

[Man do these people need a birectifier.]

The figures given in the latter case are only of comparative value. They can only be found with the same standard and a strictly identical operating method (The typical liquor was that supplied by the Central Laboratory for the Repression of Fraud.)

Curves representing the passage of the volatile elements of the brouillis during con chauffe.

I. —Brouillis:

The curves opposite give an overview of the passage of the elements during the heating to obtain the brouillis.

—Aldehydes distill at the beginning and impart to the head portions a violent odor, sometimes a strong brassy taste.
—Volatile acids are entrained throughout the heating, but especially towards the end.
—The fairly fragrant ethers, especially come first. [ethyl acetate]
—Furfurol is produced in very small quantities throughout the distillation.
—Higher alcohols, factors of vinification, are very abundant at the beginning and thereafter their quantity decreases to be canceled around 20°.

II. Bonne Chauffe:

During of this phase, evolution of the different bodies is analogous to their evolution during the brouillis, but the selection is much sharper due to the milder heating and the higher alcohol content of the products. [Milder heating implies longer time under heat which is less of a challenge to the natural reflux of the still hence a sharper selection when coupled with high ABV.]

—The aldehydes vaporize and condense at the beginning up to around 65°
—Volatile acids which are not quality factors are entrained in increasingly large quantities below 60°.
—Esters pass in large quantities at the beginning, decrease with a minimum towards 65°, then increase quite strongly below 65°. This increase results in the appearance of the taste of seconds of between 55 and 60°.
—Furfurol is found in very small quantities throughout the heating.
—Higher alcohols, abundant at the beginning, decrease to be canceled around 20°.

[The first esters they see will be only ethyl-acetate and that will change to be longer chain esters at the end. It is very interesting that they correlate longer chain esters with “seconds.” Are the esters the seconds or are they merely correlated? It is odd to see esters rejected, but many other things can run parallel.]

Practical Conclusions:

Passage of non-alcohol impureties during Charentaise distillation presents a similar appearance whatever the stills studied.

Intensity of the heating causes very noticeable differences. Rapid heating results in a very clear rise in the curve of volatile acids and ethers below 65° with the appearance of a characteristic “second” taste. Slow heating causes much less entrainment by the steam and results in a better quality product. The taste of “second” appears more slowly and faintly.

[Only around the 1950’s were some of these observations systematically studied. The Australians at Roseworthy published papers on it. The pot still basically has more reflux than you’d think and you can challenge that easily if you add too much energy. Consequently, abv drops. So when you go slow, you maximize the sublte reflux of the capital and you push back low volatility compounds that are your queue for “seconds”. So going slow, can actually give you a larger hearts fractions. UC Davis was also curious about this phenomenon and cited the Australians. It was not easy to look at because the reflux is so subtle relative to its effect on congeners.]

The removal of large quantities of head or tail products corresponds to a rectification of the brandy.

Most of the non-alcohol, in particular the more fragrant substances (aldehydes, higher alcohols, ethers) distill at the start of heating, which is why removing a large amount of head products results in an improvement of defective eaux-de-vie and a depreciation of excellent eaux-de-vie. One cannot however attribute a very great importance to the removal of the heads, because what is removed with the bon chauffe and recycled in the brouillis or the wine is found in large part at the following heating. It is in fact only a postponement and not a deletion.

[A lesson here is that the heads cut is always smaller than you think unless you have defects and then you should immediately fix your ferments for the future.]

The fact of recycling tail products results in a decrease in the amount of volatile acids and low volatile esters. This operation is always favorable to quality.

[Again, its very interesting that they are deliberately removing longer chain esters.]

As the exhaustion of these tail products is never complete and there is some left over at each heating in the vinasses, the fact of recycling them represents a purification and not a carry over as for the heads. [So head products always stay in the recycling loop, but tail products have a path of escape in the non-volatile fraction that is not recycled.]

When the wine is good, the tail products are almost always worse than the top products.

Graphics Commentary

The graphs opposite show what becomes of the volatile components of the wine during successive boiling. [graph above]

We can see that:
—Volatile acids decrease considerably.
—The ethers are considerably reduced.
—Higher alcohols and aldehydes vary little.
—Furfurol, which does not exist in wine, arises during heating in the still.

[So far they seem to be far less concerned with excessive higher alcohols than I would have thought. Maybe we’ll learn more.]

Role of Copper during Distillation

Brandy coming out of the still contains a little copper. (A few milligrams per liter). This is entrained during condensation of alcoholic vapors in the capital and serpentin. Presence of this metal is not attributable to a passage in the spirit of copper salts remaining in small quantities in the wine after fermentation. In 1952, at the Station Viticole laboratory, we carried out tests which showed that if copper salts can pass by entrainment in the brouillis, they cannot distill during bon chauffe. On the other hand, a communication on copper, its dosage, its origin and its evolution in Cognac was presented to the Société des Experts-Chimistes (1). [I think the reference to copper in the ferments has to do with copper’s use as a vineyard fungicide. They are saying don’t be concerned with a blue distillate during the stripping run because it will be removed during the second. In my experience, blue/green salts are soluble but not volatile while rust colored salts which I think are copper(II) salts are not soluble and can be racked off given time. I’ve never clarified the chemistry of the latter.]

(1) Méthodes rapides de détection et dosage du Cuivre dans les Eaux-de-vie. J. LAFON et P. COUILLAUD. Annales des Falsifications et des Fraudes n° 529-530.

During bon chauffe and especially at the end of the brouillis heating, all distillers have noticed that in the distillate, greasy particles, green or brown, are often found, retained along the walls of the alcoholmeter holder and on the filtration flannels; these very light particles float on the surface of the brouillis. [In my experience, I would not call anything greasy, but these copper salts do seem to be hydrated in a gel, but even when you think you have a lot they dehydrate to an extremely small relative amount.]

Due to the low density of these bodies, their greasy consistency and their odor becoming very quickly rancid, we thought that they were combinations of copper with the fatty acids present in the wine and carried away by the steam during distillation. [I have not observed a rancid aroma, but I would not doubt it.]

In order to determine their nature and composition, we have collected a significant amount of these substances from several distillers.

Mr. Henri Pineau, Doctor of Science, researcher, carried out the complete analysis. The latter made it possible to determine that these bodies were copper soaps with butyric, caproic, caprylic, capric and lauric acids.

These fatty acids, secreted in large part by the yeasts during fermentation, are found in the boiler, since the wines are distilled with their lees. They are entrained by steam and should end up in the brouillis and spirits. [American whiskey producers examined this topic back in 1937.]

Such acids, pure or diluted, have a very penetrating and exceedingly disagreeable odor: thus butyric acid smells of rancid butter, caproic and caprylic acid smells of sweat, capric acid smells of goats. Spirits containing these bodies would be defective.

However, copper in the boiler fixes these fatty acids and eliminates them, because the salts formed are insoluble.

Brouillis contain a quantity of these fatty substances which is all the more significant if wines used are more loaded with lees.

In the laboratory, when wine is distilled in a glass still, the previous copper combinations do not form and the distillate has an unpleasant odor. Copper is therefore a very favorable element for the quality of eaux-de-vie. The tests we have carried out with glass or stainless steel boilers have always given poor results. (Models of glass and stainless steel boilers built for the Station). [They are basically proposing that copper neutralizies excesive free longer chain fatty acids which may taint a distillate. They are leading with this idea as opposed to the conventional lead of copper neutralizing sulfur related compounds.]

Practical consequences:

All of these observations show that the copper in the still is essential for obtaining fine eaux-de-vie, and furthermore that it is necessary to very often clean the capital and serpentine with hot marc; indeed, for the copper to play its role, it must be clean and bare. [I’ve been told that their copper cleaning regimens are far more intensive than you’d think and they use large quantities of hot marc. I don’t have enough experience with very large stills, but I would think you would only want to clean any baked on organic mater. I wonder what current practices are given the expense. Andy suggests a cleaning routine illustrated here.]

The taste of “fat” found in some Cognacs is due to insufficient cleaning. In fact, the fatty acid soaps formed during the distillation stick to the walls of the Gooseneck and the coil and are only partially entrained by the vapor and the liquid. [We have found extremely “fat” character in some Arroyo style ferments. I don’t think copper is significant enough to remove it. My guess is that no cleaning is significant enough for some ferments. We observe this character even when centifuging the lees in high pH ferments. We likely need to understand cutting it away, the limits of its maturation, or how it fits into a full sensory matrix. Some of these acids can provide a low starting pH that jumpstarts maturation possibly 6 months faster, but then you may have to deal with them later…]

If the cleanings are too far from each other, these soaps become rancid under the action of air and heat. In addition, particles stuck under the cap undergo actual cooking and impart bad odors to the distillate.

Boilers used exclusively for “bon chauffe” can be cleaned every eight days. If they are used alternately to make brouillis and Cognacs, they will be cleaned before the “bon chauffe”).

If these very frequent cleanings sometimes give a certain hardness to the eaux-de-vie, it is because of the poor quality of the copper (porous, badly planed, etc.), or because the walls of the boiler are stripped. In all other cases, these are very favorable to the quality of the eau-de-vie, as several tests have shown.

Distillation Practice

The quality of the wines, in the literal sense of the word, no more than their age, should not be taken into account when it comes to distillation. Thus, the oldest and most famous wines from Bordeaux or Burgundy, while of course admitting that their market value does not prevent them from entering the distilleries, would only give eaux-de-vie with too fragrant concentration and too accentuated bouquet, inferior in a word, to those made from wines from the Cognac region which, themselves, are quite ordinary as a wine for consumption. 

For the boiler, we must look for not absolutely neutral or flat wines, but wines straight in taste, not smelling the soil and whose aroma, without being exaggerated, is quite developed and quite thin.

When should we distill?

Distillation will take place in the very period following the harvest. Indeed, in addition to the weakening in alcohol and the loss of interests occasioned by a more or less prolonged storage, old wines having acquired their characteristic bouquet, would transmit it to the brandy which, in many cases, could not to be regarded as an improvement for it.

In addition, long storage would cause maderization of white wines that do not contain sulfur dioxide, especially if their iron content is high. This maderization is unfavorable to the quality of the brandy produced.

However, only completely fermented wines should be delivered to the boiler. By subjecting wines whose fermentation is incomplete to distillation, we would lose the benefit of potential alcohol.

Changing the wine: [Vin en vindange. This may not be translated the best]

It is not possible to make a good brandy with wines that have been emptied for a long time. When distillation of a cistern or vat has to be prolonged for a long enough period, it is necessary to transfer the wine into barrels which will be kept full.

Should we rack the wines?

Pacottet and Guittonneau have carried out numerous distillation trials by adding increasing amounts of lees to clear wines. They concluded that by increasing the proportions of lees, the eaux-de-vie that are dry on the palate and have little bouquet, with clear wines, become more and more mellow with a complex bouquet varying according to the breeds of yeast used. [Reminder to track down that research paper.]

However, when the quantities of yeasts (lees) used exceed 10%, the aroma of the product becomes foul-smelling. This aroma is also unpleasant if the lees come from sick wines (pricked, turned, etc …), or wines with too accentuated character (coming from foxed grape varieties, etc …). [These opinions become very interesting because we do know that some produce lees brandy. We also know much of the acids constitute “bauer oil” which is seen as a positive but not fully understood. By foxed, I think they mean non-vitisvinifera.]

In general, it is better to put the wine separated from its coarse lees in the still, without it being absolutely clear. This can be achieved by loading the boilers with a pump whose suction hose plunger, fitted with a strainer, is kept a few centimeters from the bottom of the barrel or the tank where the wine is drawn.

When the proportion of lees in the wine exceeds 7 to 8%, it is good to leave some of it at the bottom of the barrels.

There is a case in which racking must be recommended as essential, it is that where the distiller having to “burn” quite large quantities of wine and having only a limited number of boilers, foresees that it will be in the need to extend its work until May or June. [I think by burn, they mean burn through or rush, but Andy suggested it was just an older word for distill. Distillers of yore were often referred to as burners.]

In March, wines not yet distilled will then have to be racked. Otherwise you run the risk of seeing them deteriorate or turn as a result of secondary fermentations which would not fail to occur in the spring as a result of bacteria retained in the lees, inactive during the winter period and returned to activity as a result of temperature rise.

In the case of wines made from grapes harvested from late-picked vines, it is good to rack very early.

In late processed wines, it is preferable to completely eliminate the lees. Racking will be essential whenever late sulfurization has introduced sulfur into the must. The remaining lees deposit, the alcohol content of which is negligible, can be used as an organic amendment. [I’m assuming “crus eloignes” implies late processed rather than geographically distant becaue of how they mention sulfur. I’m betting their extremely late season turns into a salvage operation.]

Cleaning the boiler:

After distillation:

It is essential to heat water before starting to distill.

To clean the coil as completely as possible and ensure its tightness, do not put water in the pipe in order to avoid condensation of the vapors. When the water vapors came out abundantly for three or four hours, the boiler is scrubbed to complete its cleaning and that of the capital. [pipe here is the serpentin tub.]

For the boiler we use a broom or a brush with a handle, with which we vigorously scrub the walls. In this way greasy and other particles are loosened and entrained when the drain valve is opened.

During distillation:

Some distillers still hesitate to recognize that it is essential to clean the distillation apparatus often. They are based on an old custom of only cleaning every eight or fifteen days.

This practice did not have serious drawbacks in the past, because the wines that were distilled at that time were not very loaded with lees, since the winegrowers disgorged the wines abundantly during fermentation (guillage).

Currently, the wine material allows the must to be extracted more completely from the grapes, and the wine contains more lees. If the cleanings are not carried out periodically, the eau-de-vie may present disgust, in particular the “grease”). [grease from “graillon”]

It is better to clean often and quickly, rather than very thorough and infrequent cleanings. We do not recommend using wire brushes.

You should not be afraid to give the brandy a brassy taste, because in any case this does not come from cleaning (the brassy taste is never related to the presence of copper in the distillate). [Yes, this was all italicized.]

Here is how it is usually done: at the end of the brouillis preceding the bon chauffe. The boiler is disassembled and rinsed with the marc using a broom or a brush with a handle; when the vinasse is removed, it is rinsed with cold water. [To spell it out, I think they rinse the wine vinasse with water before adding the marc and using the brush.]

The capital will be washed with marc (vinasse) and cold water. We will run two decaliters of boiling vinasse in the coil, then one or two decalitres of cold water to cause the dregs and the verdigris which could have formed during the previous heating. [I think the issue of flip flopping from marc to vinasse is having three autours and probably no editor. It should be noted that this is a pretty intense cleaning routine, but may improve my work as I encounter tons of verdigris in Jamaica style ferments.]

In order to carry out a complete cleaning of the coil, it will be good to plug the outlet of the latter to fill it with marc.

In some boilers, the lyne arm has an opening in its upper part that can be easily plugged. This is an important improvement which makes it possible to pour one or two decaliters of vinasse, then water, into the coil at the end of each heating.

Use only greases which do not come from petroleum residues for the lubrication of the seals of the capital. Poor quality fats can give tastes like petroleum. Greases based on silicones or paraffin do not give off bad taste.

Choice of Wine:

Wine should always be tasted before being placed in the boiler. When it is not “full of flavor”, it should not be distilled. To entrust a small quantity of disgusting wine to the boiler and not to collect the brandy it produces separately, is to run the risk of tainting the entire production. “The boiler does not purify the wine, but simply extracts the alcohol and the bouquet from which it accentuates the qualities or defects”.

When the wine has the slightest taste of “musty”, “stagnant” or “cask” it is necessary to apply immediately the common treatments recognized effective to combat these various deteriorations, so that it can be used for personal consumption and not distilled. [I wonder if personal implies cooking wine?]

When the wine comes from a harvest affected by “bad rot”, despite moderate pressing and good “disgorging”, it may be necessary to rack it before distilling. This is even more important when it comes to wine which has fermented in a tank and has not undergone disgorging.

To realize if racking is necessary, it suffices to distill comparatively the same wine, withdrawn and not withdrawn. At the tasting, the comparison of the samples will indicate the best way to proceed. [I suspsect this test is on a small scale lab still?]

When the wine is not taken directly from the barrels to load the boilers, tanks which receive it must be covered. This avoids excessive aeration of the wine which causes its maderization, in particular during years with a very ripe or rotten harvest. When the boiler is loaded, the wine must be stirred to bring the lees into suspension.

Boiler load:

Some precautions are essential.

1 ° To avoid making the boiler rhyme, it is necessary to have a very low fire at the end of heating. (Most boilers do not drain completely).

When emptying, the draft and the door openings are closed.

We can then:

—Either remove all the hot coals from the fireplace (which radically avoids all the risks of rhyming).
—Either cover the fire with briquettes or wood.

[Omitting a photo of a guy tending a fire.]

2 ° When charging the boiler, it is prudent to open the wine-heater tap, a little before having closed the drain tap. In fact, when the wine arrives in the boiler, a sudden condensation of the vapors occurs which creates a very significant vacuum with a call for air from the outside, if the outside air does not find sufficiently large openings (drain valve). ) to equalize the pressure differences between the inside and the outside of the boiler, the cap may collapse (this accident has occurred in some distilleries).

We therefore recommend:

—On the one hand, open the overflow valve before charging.
—On the other hand, do not close the drain valve until a few moments after opening the wine heater. (There is no risk of wine loss, as the suction through the drain opening is so violent that the wine cannot come out through it).

Heating Progress Updating: [Mise au Courant]

You can easily follow the progression of the vapors along the lyne arm and the pipes using your hand.

It is a good idea to turn off the draft when the vapors reach the level of the wine heater.

In the case of heating with charcoal, the best is to make a briquette blanket, on the fire, at the time of switching on.

This blanket:
1 ° Moderate the fire at the moment of setting the current.
2 ° Allows to reach the cup without touching the fire.


[long broken line] Curve representing the evolution of the degree in the alcoholmeter holder during a bon chauffe carried out with a brouillis of 32°.
[unbroken line] Curve obtained with a brouillis of 26°.
[short broken line] Curve obtained with a brouillis of 24

The preceding curves show that with a high degree of brouillis (30-32°) the head sinks to a high degree, approximately 78°. To obtain hearts with an average degree of 70°, you have to make the cut at around 54°.

With a brouillis at 27°, the head sinks towards 75.5° and with a cut towards 59-60° we obtain brandy at 70°.

With a brouillis at 24°, the head sinks at around 74°, by making the cut at 62°, one obtains brandy at 70°.

D indicates the average degree of the heart brandy.
C indicates the degree at the time of cutting.


Brouillis distillation, the only process used in the Charentes, makes it possible to obtain good quality eaux-de-vie by significantly different methods. There is no hard and fast rule and a good distiller must be able to change the way they operate according to the degree and quality of the wines. Also, the best methods to operation will not be mentioned, but simply what are the operations which can contribute to increasing the quality of the eau-de-vie and those liable to affect its fineness.

Different ways of proceeding can also have little influence on the quality of the eau-de-vie, when the wine is very frank in taste and of an average alcoholic degree. But with a mediocre wine or of a high degree, it is no longer the same.


Should we take a head at the brouillis?

We have mentioned previously that heads, which can be removed in the brouillis and recycled to the wine, always comes back to the next brouillis. It does not matter whether or not we remove heads. However, it is advisable to recycle to the wine two or three liters which flow out at the start of heating and which washed the coil and entrained the tail products from the previous heating which remained inside. At the same time, heads recycled in the wine undergo modifications and improvements during the following heating (hydrolysis). [The chemistry of this last comment is a little interesting. All that I think would under go hydrolysis is ethyl acetate splitting and thus the free acetic acid being far less volatile and either becoming a part of the tails or staying in the wine and never reaching the distillate. I think their comment is a little armchair speculation.]

Should we take a tails cut?

Liquid that condenses at the end of the so-called “tail” usually has an unpleasant odor and a herbal, bitter flavor. Many stills have found the generally deleterious influence of tailings on the quality of the brandy when these “tails” are used with brouillis.

We have verified these findings by bringing the degree of a certain quantity of “tails” to 27° with extra neutral alcohol. The artificial brouillis thus obtained was distilled and hearts at 70° were collected. Liquid thus obtained had an unpleasant flavor and odor. This proves the unfavorable influence of tails used with brouillis. The first precaution for making an eau-de therefore consists in collecting the brouillis tails apart and recycling them with the next wine. [I would say that nothing here is hard and fast and that similar exploration should be done for every substrate.]

This recycling effectively results in a purification and not by a simple transfer from one heating to the other as in the case of the heads, because the tail products are not very volatile and at each heating there remains a significant proportion in the vinasses. [This is their logic for why hydrolysis may be the benefit of recycling heads.]

To what degree should we remove the tails to recycle them with wine?

[Omitted is a photograph of a still parrot described as a “hydrometer port”.

Whenever possible, your best bet is to collect the tails from a high degree. The degree of brouillis is thus raised, which is not too important when distilling wines at a low degree; on the other hand, if we are dealing with wines of a high degree, there is a risk of obtaining a mixture of a degree that is far too high. [You would think they could easily water back between distillations, but that may break aroma to a meaningful degree.]

So :
—The tails can be taken at around 6 to 8° when the wines used have an alcohol content of 7 to 8°.

—When the wines measure 9 to 9.5°, it is preferable to take tails from 4°. (However, tails can be taken to a higher degree in the case of mediocre wines). —When the wines are 11° we can take the tails only from 2°.

Degree of brouillis:

The degree of brouillis is all the higher as the wines are themselves richer in alcohol.

The lower the degree of brouillis, the more the eau-de-vie obtained is rectified and fine, because the quantity of hearts spirit collected from a weak brouillis is proportionally much lower than that obtained from high degree brouillis. 

With weak broillis we have to make the cut at the bon chaffe to a high degree (see curves and comments) we do not risk having a taste of seconds. [seconds being the terms for tails from the second stage of distillation. Andy mentions some distilling schemes that take both seconds and tails and provides some numbers:
Bonne chaufe
Heads: 15 to 25 liters
Heart: 680 liters
Seconds: 650 liters
Tails: 100 liters
Vinasses: 10.7 hl.

I would bet seconds and tails are differentiated because of where they are recycled to.]

When we distill low-degree wines, naturally, low-level brouillis is obtained; All is for the best. On the other hand, with wines of 10° or 11° one obtains a high degree brouillis of 30-32 ° and even 35°.

Except in exceptional cases (excellent vintage, very healthy harvest and very slow distillation), it is rare to obtain very good eaux-de-vie with brouillis grading more than 30°. [I’m betting this idea has been challenged over the years.]

In this case, they can be reduced to a maximum degree of 29°, with very pure water. However, we must not use more than 10% water, otherwise we dilute the brouillis too much which gives eaux-de-vie poor in ethers and lacking in fragrance and body. [The higher value esters break via hydrolysis.]

When the eaux-de-vie are low in esters (very ripe grapes for example), it is often preferable not to put water in the brouillis and to make eaux-de-vie at a higher degree (70.5° and even 71°). [Fascinating advice as they have downplayed esters earlier.]

In the most late harvested vintages, it is almost always preferable to make eaux-de-vie at a degree greater than 70°.

Using the Seconds:

Some distillers mix with their brouillis the heads and the seconds of the bon chauffe. In this case, it is good to distribute the second in the whole of the brouillis and not to make a bon chauffe with two seconds. This process gives good eaux-de-vie when we use excellent wines from very good vintages; it has the advantage of making it easy to keep the management accounts. In addition, it is the most economical process due to its speed. It is necessary, in this case absolutely to avoid knocking the furnace. [knock the furnace is arrived at from “les coups de feau.”]

Other distillers, after switching off the bon chauffe, fill the boiler with wine, this is what they call “loading onto marc”. In this case, it is useful to take a large tail at the end of heating. [loading onto marc is taken from “charger sur marc”. I have not heard of this technique but it is very cool.]

Finally, a certain number of others looking for more finesse, recycle with wine the seconds of the bon chauffe. They very often obtain eaux-de-vie of rare quality. [The significance here is that these seconds are not recycled back into the broulis for the next bon chauffe, but rather a step further with the wine.]

This process has the drawback, however, of significantly increasing the degree of wine placed in the boiler. This results in high degree brouillis which it is generally necessary to reduce. When we distill very alcoholic wines we can be led to use very large quantities of reduction water and we can thus obtain eaux-de-vie which are certainly fine, but short and aging very slowly (eaux-de-vie lacking in esters).

This is the process of choice, whenever we need to distill mediocre or low-grade wines. It should be used with caution when it comes to highly alcoholic wines. [It is very interesting that they worry about ester breakage within the double distillation process. They are also also generally pessimistic about esters forming in the still.]


Avoid overheating the wine pre-heater.

Vapors must not be passed inside it when it is empty, otherwise there is a risk of cooking the dregs deposited on the pipe which crosses it and of communicating to the wine and then to the brandy the taste of cooked lees. It is good not to pass the vapors into it until the end of heating.

A good precaution consists in taking the average degree of brouillis (by making the temperature correction) before each setting in the boiler and when this degree exceeds 27° to reduce it by adding very pure water (without however exceeding a maximum of 10%).

Bonne Chauffe:

Liquid which flows at the start of heating, called the “heads”, contains volatile substances with a penetrating odor which can affect the fineness of the eau-de-vie. In addition, this liquid dissolves the tail products from the previous heating which can remain on the walls of the coil. As the head contains bodies which participate in aging, when the wines are of excellent quality it is not advisable to take more than half a liter or one liter per hectolitre of the capacity of the boiler. When the wines are defective or mediocre, we can remove up to two liters per hectolitre. However, do not expect too much from purifying these head products by putting them back in the wine or brouillis, because they generally reappear at the top at the following heating. If you really want to purify a defective eau-de-vie, you have to permanently eliminate the heads without recycling them or bringing them together with the tails to make a special heating that will be recycled with wine. [Volumetrically this is very inline with Arroyo’s recommendation for taking heads. One thing to note is that if the congener in question is aldehydes, they could be reycled with an active ferment and yeast can convert the aldehydes back to ethanol. This technique was developed at UC Davis and used to add economy to neutral spirits production. Cognac can not use such a process because they have a unique season and do not ferment all year long.] 

Coupe : [as in coup de tête or coup de grâce; the decisive action or death blow… Coupe could probably be translated as cut.]

The moment when the good brandy is separated from the seconds is called “the cut”.

In the past, we used to cut with the “pearl”.

The “pearl” is obtained by striking on the palm of the hand a “taupette” containing brandy, stoppered with the thumb. When the bubbles formed in this way rise slowly and remain on the surface, we have the “pearl”. This generally occurs when the liquid flowing through the coil has a content of 58 to 59° depending on the wine and the year. At this time, the eau-de-vie collected inside the barrel has a content of 60 to 71°. [A taupette is likely a glass vial. Forming the pearl is about surface tension and long chain congeners contribute just as much as ethanol.]

At the present time, distillers make the cut by using a hydrometer and deciding by tasting. (We must not forget to make the correction due to the temperature which can be very important).

You should never make the cut below 58° (extreme limit 57°) even if this leads to making brandy at 70.5° or 71°.

Indeed, if the cut is made to a degree less than 57°, all the brandy can be tainted with a very defective seconds taste. (Depending on the degrees of brouillis and the heating routine, the taste of seconds appears between 58 and 60°) A very slow distillation allows the cut to be made at a lower degree.

Small capacity boilers (3-6 hectos) further rectify the eaux-de-vie due to the very large cooling surface of the capital compared to the volume of liquid. This results in a very rapid drop in the degree from 61°. The taste of “seconds” appears more quickly and more markedly than in large capacity boilers; in this case it is preferable to make the cut around 6o°. [This is a fascinating note that hopefully will help someone working with a small still. It is often taken for granted the significant degree that pot still designs create reflux.]

Refreshing the Pipes: [This pipe is the tub that holds the serpentin coil.]

When starting to distill, make sure that the coil turns are not covered with a lime deposit. In our region, where the hydrotimetric degree of water is generally high, deposits occur very abundantly and very quickly, and make the condensation of alcoholic vapors difficult and irregular.

It is essential that the vapors condense gradually and regularly. Refreshing the tub immediately changes the flow rate of the coil and alters the flavor of the flowing liquid. On the other hand, experience has shown that the brandy which leaves the coil should preferably be at a temperature between 18 and 20°.

When the eau-de-vie is collected at a temperature that is too cold, that is to say less than 15°, it has the defect of being “hard”. Above 25° there are appreciable losses (1).

(1) Indirect Contributions allow a maximum evaporation of 3%.

To ensure that the brandy flows more or less regularly, a good precaution consists in refreshing the “tub” before setting the flow; then, we will not have to refresh until after the cut.

Fire management:

For “bon chauffe”, the distiller must prepare his fire in such a way that:

—The boiler slowly comes up to speed.
—That from this moment, they no longer have to open the door of their stove to touch the fire, but simply to adjust its intensity by the pull tab placed in the chimney (this recommendation is especially important for small boilers).

It is important to be careful not to open the door, or to put in additional fuel shortly before cutting: there is a risk of introducing an excess of heat causing the entrainment of heavy materials which always give a special taste to the eau-de-vie and reduces its fineness (for large-capacity boilers heated with wood, it is often impossible to get to the cut without adding wood). [Increasing the energy challenges reflux and lowers your distillation ABV during a phase that is extremely sensitive to changes in ABV. It has been interesting to observe the transition of high value congeners during birectifier fraction from 4 to 5. High value aroma, in fraction 5, also appears in a narrow band then typically is exhausted. I do not believe they are splitting hairs.]

We must try to obtain a regular flow to the coil, we get there with a little practice. For this it is necessary to see the liquid.

The above curves show the passage of volatile acids during bon chauffe. It is observed that they pass in an increasingly large quantity below 65°. The curves were established with 3 different heating speeds: the lower curve with the boiler heated very slowly, the middle one with medium heating, the upper one with rapid heating.

It can thus be seen that it is preferable to heat slowly, because a smaller quantity of volatile acids is obtained in the spirit. We know in fact that in new brandy, volatile acids are not favorable to the quality.

Heating duration:

The time required to obtain brouillis varies according to the capacity of the boilers and the degree of wine. It is seven to 10 hours for a ten hectoliters boiler. The “bon chauffe” requires, for a boiler of the same capacity, from twelve to fourteen hours. Some distillers make it last twenty to twenty-two hours and obtain remarkable eaux-de-vie. The essential point is that the flow of the coil is as regular as possible. The attention of the distiller should often be paid to the temperature and size of the jet of the liquid flowing out.

It is necessary to heat all the more gently as the boiler has a lower capacity.

Wood, Coal, Oil:

As charcoal has a slightly higher caloric power than wood, adjusting the heat requires a certain skill that a careful distiller quickly acquires. When the boiler is correctly ramped up, distillate is very easily collected completely without touching the fire. The heat of the charcoal is softened by the vapors of the water placed in the ashtray which at the same time protect the bars of the grates of the furnace.

In the case of heating with charcoal, we generally count that 100 kg of charcoal can produce one hectolitre of Cognac at 70°.

Fuel oil has recently been used in a few distilleries. It has a few advantages: cleanliness, easy monitoring, regular heating. However, the installation is expensive and it is necessary to eliminate all contact of the brandy with these fuel oil vapors, finally, it is to be feared that the boiler bottoms will have a shorter duration, the fuel oil slightly attacking these. It is also difficult to eliminate any fuel oil odor, the odor being able to permeate the clothes of the personnel responsible for carrying out the distillation.

If it weren’t for the cost issue, butane or, better, propane gas would be very interesting because they allow very regular heating. Lacq’s gas, if its price becomes sufficiently low, and if it is suitably desulfurized, would be usable. [It would be interesting to follow up and see how the industry changed in this regard.]

Faults: [Dégoûts]

Brass. —It depends: [Brass here is not be talking about the material, but rather a fault.]
—Poor quality of copper.
—Lack of cleaning of the coil inside which it is always forms a lot of “verdigris”.

—Too vigorous cleaning of the boiler with metal brushes, which scratch the copper.
—Absence of cleaning the rear. [De l’absence d’un prélèvement de queues.]

The brass never comes from too frequent cleaning, but rather from the lack of cleaning.

Cooked. —It is observed:

—When the boiler has a too thin bottom and especially when it becomes concave.
—When you start to distill again, after a short break, without completely cleaning the device.
—When the fire towers are placed too high.
—When the steam is passed through the wine pre-heater when it is empty.
—When the wine contains an excess of lees.

Rimé. —It may depend on: [Rimé may best though of as a ring of scorched grime.]

—From an excess of lees.
—A boiler planing fault.
—Insufficient cleaning, the lees remaining stuck to the bottom and rivets.
—Fire towers placed too high and insufficient protection of the drain pipe.

In all cases, rimé is produced by excess heat. Riméing generally occurs in front of the chimney, where the gases continue to ignite on contact with the circulating air or at the drain pipe. Of all faults, riméing is the worst, and it should be seen as impossible to correct. A few centimeters of “rimé” are enough to communicate to all boilers, permanently, that special taste, and the stain always gets bigger. When the boiler has riméd, it is necessary to vigorously scrape it and carefully replane the scraped parts.

[Riméing in this desciption almost seems to be a rim of scorched lees. You would likely get an off aroma similar to “tufo” in addition to a more burnt character. These same phenomena plagued Jamaica rum until the mid 19th century when many direct fire stills were converted to steam driven.]


Some wines may contain small amounts of sulfur due to too late sulfurization. In particular, the very adherent wettable sulfur treatments carried out in the vicinity of veraison. This sulfur is transformed by reduction into hydrogen sulfide during fermentation. The brouillis obtained by distilling these wines have a characteristic smell of rotten eggs. On contact with copper, black sulphides are formed on the walls of the boiler. Frequent and vigorous cleanings are necessary to remove them.

Hydrogen sulfide odor can be removed from the brouillis by contacting them with a significant amount of copper turnings which binds the foul-smelling hydrogen sulfide in the form of insoluble black copper sulfide.

When one notices the defect of the wine before distillation, the best is to separate it from its lees and to aerate it strongly.


The smell of grillé comes from projected lees particles cooking onto the sides of the capital.

General advice for making good Eaux-de-vie with normal wines

—Never leave receptacles containing wine empty.
—Only use wines that are perfectly healthy and straight in taste.
—Frequently clean the different parts of the boiler, especially as the wines are more loaded with lees.
—Distill slowly and without undulating heat.
—Moderately heat the wine heater.
—Do not pass steam through the wine heater when it is empty.

Brouillis :

—Eliminate the few liters of heads that will have washed the coil and rinsed the tails from the previous heating that remained there.
—Pass the tails back in the wine.
These tails will be cut:
—Around 4° if the wine has a high degree (9.5°-10°).
—Around 7° if the wine is weak (7-8°).
—Avoid housing the brouillis in ordinary cement tanks.

Bonne Chauffe :

—Make the heatup slow. [taken from: Faire une mis au courant lente]
—Cool the condensing tub before heating.
—Eliminate 0.5 to 1.5% of heads according to their quality.
—Always cut above 58°. Otherwise, taste to avoid “seconds”.
Collect the brandy in the alcoholmeter holder at a temperature between 18 and 20°.
—Touch the fire as little as possible before cutting.

Rules determining the degree to which one must make the cut to have Eau-de-vie at 70°

The degree of the heads brandy is noted, for example 75°. We differentiate between this degree and the average degree, such as one wishes to obtain it, of hearts brandy (70° for example).

75 — 70 = 5

This difference multiplied by 2 (5X2 = 10) must be subtracted from the average degree of the hearts spirit.

70 — 10 = 60

This fairly reliably achieves the degree to which the cut is to be made.

[Average degree of Brouillis
Degree of good heating heads
Degree to which we must make the cut to obtain brandy at 70°
à éviter = to avoid]

The degrees shown above represent actual strength. These degrees vary slightly depending on the heating speed and the capacity of the boiler.

Distillation in years of decay [better said as salvage?]

As a result of the findings made during the years of intense rot invasion, it is advisable to only distill wines from completely healthy harvests with their lees.

With regard to wines from harvests in a “good rotten” state (noble rot and gray rot), it is recommended to do, at the start of the distillation: [gray rot taken from “détech de pourriture grise. I had never heard of anyone distilling noble rot grapes.]

—A bon chauffe with brouillis from the wine mixed with its lees (coarse lees excepted).
—A bon chauffe with a brouillis of racked wine.
(These distillations can be carried out at the Station Viticole in small laboratory stills).
The comparison of the eaux-de-vie obtained will make it possible to determine the method to be used.
Tasting can bring out three different cases:

First case:

Brandy obtained with the wine mixed with its lees has a “clear” flavor. In this case, the winemaker will continue to distill with part of the lees. This is the usual distillation of wines from a healthy harvest.

Second case:

Brandy obtained with the wine mixed with its lees has a flavor lacking in “sharpness” or the more or less accentuated taste of “rot”. By comparing this sample to the brandy obtained with the same wine, drawn off, the taster can see if the lack of sharpness or the disgust comes from the lees. If the brandy racked wine, although shorter and a little less spicy, has a “clean” flavor, there is no hesitation, it must be distilled without lees and cut to taste.

Third case:

The eaux-de-vie made from the same wine, one distilled with its lees and the other without lees, have a more or less pronounced “rotten” taste. In this case the wine must be considered as unfit for distillation and be processed for personal consumption. [We still dont’ really know what personal consumption entails.]

Indeed, following harvests that were too late, if grapes in the state of putrid rot, black rot, or “mold” were not removed from the harvest by careful sorting, all of the wine was spoiled. These alterations which, quite often, are difficult to perceive when tasting the wine, always are clearly found in the eau-de-vie as they are highlighted by distillation.

When should we rack the wines from harvests affected by rot?

—When the aforementioned distillation tests have shown that the wine must be distilled without lees, racking must be carried out, preferably immediately after the first period of cold, which occurs after the end of fermentation. This will prevent secondary fermentations of microbial origin, which always occurs in wines not racked, during the winter, after a rise in temperature, as it happens quite often at the time of “crues”.  [#SOS Crues is hard to translate. Could it floods are thaws?]

Distillation to Taste

Some distillers, but insufficiently many, “taste” the “bon chauffe” to make the different cuts (head and seconds). At the “brouillis”, they most often take, without tasting, a little “heads” (some do not) and “cut” towards the end of the “boiling” to a degree which depends on that of the wine, in order to obtain brouillis grading from 26 to 28°.

In years of completely healthy harvests, this way of proceeding is good, but in years when the grapes are partly spoiled by various causes: Cochylis and Eudémis, Mildew of the bunch (1930-1932), rots (1933-1934 ) or hail, it is insufficient to obtain the maximum quality.

The “to taste” method of distillation, practiced by the best distillers, consists of smelling and tasting all the “brouillis” as well as all the “bon chauffes” to determine the best times to make the “cuts”.

When the harvest is healthy, the quantity of “head” to be taken from the brouillis is often reduced to a few liters; on the other hand, when the grapes are spoiled, in particular in a year of rot invasion, due to the often nauseating odor and the acrid and bitter flavor at the start of heating, the distiller may be required to take up to two liters and more of “heads” per hectolitre of capacity of the boiler. [The nauseating odor is very likely acetaldehyde above a certain threshold. I have only experienced it when redistilling a saunterns as an experiment. However, much of the aroma went away after a few months as half became acetal.]

For the “heads” of bon chauffes (healthy harvests) the distiller takes a maximum of one liter, per hectolitre of capacity of the boiler, while in the year of rotting (1933-1934), it can be brought, by tasting to increase and sometimes to double this levy.

Likewise, for the “cut” of the “bon chauffes”, the distiller must taste often, in order to avoid the taste of “seconds” and other faults which do not always occur to the same degree.

All the distillers have observed that before the “cut”, the liquid which flows between 63° and 58° (depending on the degree of brouillis) is sometimes of excellent quality, sometimes fair, sometimes bad and that the taste of “secondis sometimes preceded or accompanied by various faults corresponding either to the deterioration of the harvest, or to faulty vinification or poor accommodation of the wine.

Under these conditions, one understands the interests of the distillation “to taste” method, to determine for each heating the most favorable moment to carry out the “cuts”.

The “heads”, the “tails” of the brouillis, as well as the “seconds” of the bon chauffe must be recycled with the next wine; this resulted in a purification which generally has a favorable influence on the fineness of the eau-de-vie.

In a year of damaged harvest, it is especially recommended to conduct the fire in such a way that the boilers “ramp up” very slowly, which allows the heads products to be separated well, which are often very unfavorable to the fineness and to the the quality of the brandy. [This separation of heads products relies on the natural reflux of the still not being overly challenged hence the gentle heating.] 

After the “cut” of the bon chauffe, it is necessary to avoid doing what a very large number of distillers do and which consists in activating the fire too much, because a very rapid boiling causes the entrainment of defective tail products. This is of little importance when we recycled the seconds with the wine but becomes important when we use them with the brouillis.


When the eaux-de-vie obtained do not show any marked faults, but only lack a little “sharpness”, it is recommended that they be redistilled. This method has been recommended by experienced practitioners.

To redistill a brandy, it suffices to reduce it to the degree of an ordinary brouillis (26 to 28°), with distilled water or rain water collected in a container of impeccable cleanliness. Special attention must be paid by the distiller to the different “cuts” which must be “to taste”.

Here, as an indication, the appreciations at the tasting and the analyzes:

[Brandy obtained by distilling with its lees a wine made from grapes affected by gray rot
Brandy obtained after redistillation of the previous brandy
Tasting: Brandy lacking in sharpness. Ample but common bouquet.
Slight rotten taste. Brandy without faults, bouquet lacking a little distinction.]

Only the amount of volatile acids decreased due to redistillation. This is the main cause of the improvement produced, because most of the volatile acids affect the fineness of the eau-de-vie; the amount of ethers changed little, the higher alcohols remained the same.

These findings show that eaux-de-vie can be improved by redistillation without the “non-alcohol” being changed very appreciably.

Cut and “briefing” warning devices

During bon chauffe, if the cut is made too late, the brandy can taste like “seconds”. This taste depreciates all of the Cognac stored in the same barrel.

Any distiller who closely follows the progress of his boilers, knowing the pace of the still, knows roughly what time the cut will take place.

Knowing the degree of the heads, the distiller deduces from it the degree to which they will have to “cut” so that the whole of the “hearts” brandy is 70°. As they do not want to let the moment of the cut whose importance is known pass, they consults the alcoholmeter well before the scheduled time.

If there are several boilers to supervise at the same time, this does not always leave them free to carry out certain essential work (cleaning or moving drums, transporting coal, etc.). In any case, they are not immune to a fortuitous delay or a distraction.

It is therefore not without interest to have a simple device warning the distiller when they must make the cut. This device can render notable services in particular at night.

M. Sabourrau showed us an ingenious device produced in the last century by M. Bertrand, from Surgères. It is a copper float placed in the alcoholmeter holder, a float which, under pressure of the liquid, mechanically cuts to a determined degree. Mr. Paul Beau has successfully used a similar apparatus.

As many distillers involve tasting to make decisions, it seemed preferable to keep a certain latitude for the distiller to perform the cut and to warn him instead of carrying out the operation mechanically, therefore blindly.

The attached photo represents a device capable of fulfilling this function.

This is a contactor placed above the alcoholmeter holder.

On the way up, the alcoholmeter stem engages in a funnel guide and brings into contact two metal blades which close the electrical circuit of a bell. This then starts ringing thanks to a battery.

The degree to which the bell should sound is adjusted by sliding the switch along the support strip.

At night, this device can be more useful than an alarm clock, because it warns the distiller just when and for as long as necessary, since the ringing does not stop until the switch is closed.

This device has given good results for ten years and has been tried with success by many distillers.

The same device can be designed to actuate an electromagnet which automatically performs the cut.

[Omitted a photo of the primitive electrical box for a warning system.]

After loading, “heat up” takes half an hour to an hour depending on the boilers. It is necessary to frequently touch the Gooseneck and the pipes with the hand to follow progression of the alcoholic vapors and to close the draft and openings of the furnace doors, when the vapors reach the level of the wine pre-heater, in order to avoid too violent fire passing the wine or the brouillis to the condensing coil (especially when the heating is carried out with wood).

A bimetallic strip welded to the pipe at the level of the coil and connected to a bell constitutes a simple warning device for the distillate starting. The buzzer sounds when the pipe heats up under the action of steam.

A cut warning device with a photoelectric cell is currently under study. This device will be more stable and more sensitive.

Recovery of Calories and Residues Lost during Distillation

During distillation a lot of heat is lost which can be at least partially recovered.

Sources of recoverable calories:

You can collect boiler vinasse after the wine has been heated.

Indeed, each heating releases 2 to 6 hl. of boiling marc according to the capacity of the boiler. This marc residue from the distillation of the wine which leaves the boiler at 90° especially contains, in addition to some fertilizing elements, potassium bitartrate and tartaric acid in solution.

In the past, the marc was treated with lime to obtain lime tartrate which was then collected at the property and shipped through wholesalers to the tartaric acid factories. [This acid was likely used in the baking industry.]

This process was invented by Ordonneau, Pharmacien-Chimiste, in Cognac and for many years was very profitable, to the point that the sale of lime tartrate came to pay for a large part of the coal used for distillation. [There is the incredible story of Antonio Perelli-Minetti buying up whole wineries from occupants who were fleeing a California earth quake and selling their properties for pennies on the dollar. He paid off the debt for quite a few by climbing into the vats and scraping up all the tartrates and selling them to the baking industry. Ordonneau was one fo the first scientists in the late 19th century to recognize both Cognac and rum oil.]

As a result of the increase in the price of transport and new production by synthesis of tartaric acid, production of lime tartrate is no longer profitable at present.

This is why, as pointed out in 1903 by MM. Guillon and Gouirand in the Revue de Viticulture, we could use boiler pomace as fertilizer by spreading it on manure. The fertilizer content of the marc is not negligible. It is appreciably similar to the composition of liquid manure, that is to say in the order of:

N 1 %, P 2 .05 1.50 % and K 2.0 1 %

This hot marc is interesting, not only for the fertilizing elements it provides, but also for the heat it provides, when used to water the manure, heat which favors the fermentation of artificial and ordinary manure.

In fact, methane fermentation (straw manure) is sometimes difficult to provoke, especially in winter, and a supply of calories favors its start.

A Cognac industrialist thought of this recovery and successfully uses hot pomace for watering artificial manure. However, it is essential to neutralize it with slaked lime, because an acidic environment would prevent the fermentation of the manure. The lime expenditure is not considerable of the order of 1 kilo per hecto of marc.

Now let’s take a look at other heat sources that are larger and easier to recover.

This is the hot water from the top of the condensing tubs. Without doubt, in certain distillers, in properties where there is a lack of water, this water is sent to cooling slabs to lose its heat and to be able to be used again for condensing distillate.

It is obviously not easy in this case to recover these calories. Very often, however, the cooling pipes are constantly supplied with cold water.

What is the recoverable hot water flow in this case?

It can be assumed that boilers of 10 hl for example, well adjusted for a flow rate of the distillate at a temperature of 15 to 18°, require for their cooling, a fresh water intake of more than 40 hl per day.

Consequently, there is a discharge of 40 hl of water, the temperature of which exceeds 70° at the top of the condensing tub.

If the distillery has several boilers, the daily output is multiplied by the number of boilers. With 4 boilers, we therefore obtain around 160 hl of water at 70° per day.

What can be done with this hot water at 70°?

When it comes to on-farm recovery, from distillers, here are some of the possible recoveries:

Why not install a laundry with hot running water, which could be used by all the inhabitants of the farm (1). [my first thought was partner with a laundromat!]

(1) Mr. Henri Faure, manager, had a wash house and laundry facilities installed in a property in Malaville for this purpose.

When the boiler (which is unfortunately the less frequent case) is above the level of the house and near the back, we could without great expense, install a hot water supply in the farm.

A central heating system can even be implemented. (For very hard water, some precautions should be observed to avoid obstruction of the pipes by scale deposits) (2).

(2) Mr. Blois, distiller, installed central heating and showers.

Many other even more agricultural uses of these calories can be envisioned. Here are a few :

Stratification des greffes en chambre chaude, installation de couveuses, etc…, etc…

Why also, if we have several boilers, not to install bath-showers, even very rudimentary, from which everyone on the farm could benefit at no cost apart from the installation costs.

The workers of the towns have many similar installations, life in the country does not exclude the interest of hygienic care.

Unfortunately, it is not possible to create this comfort everywhere, for economic reasons. But where there is a boiler that makes hot water and when it gets lost, why not use it? Since apart from the installation costs, the cost price is zero.

[Omitting a photo of a man with an impressive mustache drinking Cognac from a tasting glass.]

Tasting of new eaux-de-vie

Tasting is a difficult art which requires certain gifts and a much experience. A great sensitivity of the senses must be combined with the exact memory of sensations. Only a great habit allows us to make sure judgments.

Value of the results obtained will depend not only on the sensitivity and the perfection of the taster, but also on transient causes which can influence sensation and perception.

Among the possible causes of errors, we must first point out the state of health of the organs of the senses (cold for example). In addition, various influences can distort judgment.

The sense organs do not reach maximum sensitivity until after one or two samples. Also, it is advisable to come back to the first impressions, corresponding to the warm-up period.

Conversely, sensitivity can be blunted by too many repeated excitations. Tasters with little training should therefore only taste a limited number of samples per session.

If you first taste a product with a great intensity of flavor or bouquet, then you no longer grasp the nuances. This is why the samples to be examined should be graded in order of increasing taste intensity.

Finally, fatigue has a profound impact on impressions.

Attention has a considerable effect on the intensity of perceptions, whether it has not been awakened or has been distracted by some external cause. Hence the need to focus all of your attention on the points you need to look for and at the same time to remove any cause of distraction (conversation, noise, etc.).

It is also advisable to avoid external suggestions, or autosuggestions. It is therefore important to eliminate the influence exerted by labels, opinions expressed, etc.

Memory plays an important role in perception, since we compare, consciously or unconsciously, the sensations perceived with those experienced previously. The ideal is to be able to compare impressions straight away, that is to say to proceed with the tasting with samples which serve as witnesses, as a reference.

[Omitting a photo of a tulip tasting glass holding Cognac.]

If one of the impressions is clearly dominant, it can interfere with the perception of others. A musty and especially pronounced corky taste, for example, can mask any other finding. In strong spirits, the impression of alcohol is so violent that it no longer allows other bodies to manifest. This is the reason why we can dilute alcohols to appreciate them…

Finally, habit makes certain tastes considered otherwise unpleasant or even repulsive to be accepted as normal.

Practice of tasting:

Eaux-de-vie are generally tasted in a special glass, with thin walls, narrowing at the top, so as to concentrate the odors in the nose.

We don’t usually choose where to taste. However, it is necessary to stay away from violent odors. It would be best to taste in a special temperate room. In a distillery you taste very poorly.

The best time to do the tasting is in the morning. After meals, the sensitivity of smell and taste is strongly blunted, especially in smokers and people who have consumed foods spiced or seasoned with garlic. You should avoid smoking before tasting.

The olfactory examination must precede that of gustation, otherwise the discrimination of odors is less clear.

Only a small quantity of brandy should be taken for tasting and always the same as much as possible.

To highlight aromas, sometimes masked by alcohol, some tasters advise to pour a few drops of liquid in the palm of your hand, then rub the two palms together to cause the alcohol to evaporate. What remains is a bouquet that is then easier to appreciate. This practice does not seem necessary in the case of Cognac.

Another process consists of pouring brandy into a glass, then emptying it and covering it with a sheet of paper laid flat. After several hours, when the alcohol has partly evaporated, you can smell the contents of the glass. [This is famously done with a watch glass and is a great way to observe high value aroma. Some rums can last for days while other spirits cannot.]

Gustatory examination can be carried out on the product as it is, or diluted with water, if the degree seems too high.

Very pure, cool or better still lukewarm water is then used, so that the brandy is brought to a measure of around 30° and at a temperature of 25-30°. The contents of the glass are stirred vigorously and the scent is observed by moving the nose as deeply as possible into the glass. Then we notice the taste, by putting a small quantity of liquid in the mouth which we then reject: we note the impression on the palate, the taste and the aftertaste.

Cognac eau-de-vie:

The two main qualities of the new Cognac eau-de-vie must be finesse and body. The finesse consists in the clarity of the bouquet and the taste which distinguishes good Cognac from mediocre eaux-de-vie. [This clarity issue may parallel some of the contrast enhancement ideas I have held for gin. Basically ordinary congeners can sort of cast olfactory shadows. Contrast is enhanced by removing them. With Cognac, the main issue seems to be long chain acids. When they emphasize distillation on the lees, they want soem major asset, but are away of the liabilities of too much affecting the “clarity”.]

The lack of sharpness can come from:
—damaged harvests;

—bad wines (vinification, accommodation, etc.);
—defective distillation or storage of the brandy.

The body is the quality that differentiates good Cognac brandy from other alcohols. [much of this “body” concept will parallel the “radiance” concept observed in rum.]

If you take a few drops of an alcohol on the tongue that is not Cognac, you feel a burning sensation. Real Cognac, on the contrary, slowly evaporates, blossoming throughout the palate. The spirit that lacks body is dry and short, which is the hallmark of commercial alcohol.

Each vintage has specific characteristics. Thus the new Grande Champagne brandy often has a little less body than that of certain other crus, but has a bouquet that is at the same time more powerful, finer and more subtle, it ages more slowly, but acquires a incomparable bouquet.

Main faults that can be found in new eaux-de-vie


The feeling of acidity is caused by the presence of hydrogen ions. It is felt on the tip of the tongue. If it is not exaggerated the acidity gives body to brandy.

Flat: [Sometimes said as flabby.]

Said of a product devoid of flavor due to a lack of acidity.


The musty taste and smell is caused by the secretions of a penicillium. The musty essence which only distils at 270 ° is however entrained by the steam during the distillation. [I have seen photos of molds growing on long duration open culture rum ferments and have wondered if they convey a moldy taste that does not help the rum.]

Pricked or “pointed”.

Characterizes the smell and taste of vinegar. The sharpness is due to ethyl acetate, produced by Mycoderma aceti. It appears in the heads during the heating.

Sharp: [taken from “Fûté”]

Comes from a poorly maintained barrel: overcharred wood.

Stagnant: [taken from “Croupi”]

Reminiscent of the foul odor given off by stagnant water in which microorganisms swarm.

Cooked: [possibly better said as baked?]

The cooked taste results from oxidation in contact with air at high temperatures of various plant elements.

Rimé :

Rimé is one of the most serious faults; it cannot be removed even by diluting it in large amounts of healthy brandy.

It results from heating in a too thin layer of a liquid containing organic bodies in suspension (lees, etc.). The rimé taste is analogous to that which occurs in an overheated bottom of a saucepan.


Bitterness characterizes products with a taste reminiscent of quinine. It is found in the aftertaste. The feeling of bitterness in spirits is usually caused by volatile acids such as butyric and propionic acid. It is often due to secondary fermentation by bacteria such as “souring” in wines that are insufficiently acidic or come from grapes affected by rotting.

Green taste:

Herbaceous taste, reminiscent of crushed leaves. This taste seems to come from too violent pressing of the stems during the harvest, or from the abuse of nitrogenous fertilizers.

Styptic: [Metallic? can’t decide on this one.]

Taste picked up in the throat and has a metallic flavor (iron).


Off-putting smell and taste of spoiled organic material.

Brass taste:

Flavor evoking a prolonged stay in a copper container.

This taste due to an aldehyde compound comes first and disappears during aging. [I’m not sure what aldehyde they could be referring too but upon aging half of the aldehydes come to equilibrium as acetals and exhibit a dramatic change in how we perceive them.]

Fat taste:

Fat flavor having started to go rancid in the air. It is due to poor cleaning of the still.

Seconds taste:

Greasy flavor, lacking in sharpness, due to fatty substances; it appears after or at the time of cutting.

Hydrogen sulfide odor:

Rotten egg smell caused by the presence of hydrogen sulfide. Hydrogen sulfide can be formed during the fermentation of wines from vines sulfured too late in the season.

Fuel oil smell:

This taste, which masks the real taste and fragrance of the eau-de-vie, comes from the distillation of a wine which has come into contact with lubricating oil: (in the case, for example, where the pressing has carried out with petroleum lubricated mechanism). Only paraffin oil should be used in the case of lubrication. [mechanism was adapted from verrin which I think implies a hydrolic pressing cylinder.]

Terroir aroma: [Older definition of the terroir term is often a fault. Andy Garrison points us to Geosmin which can be a flaw in spirits that comes from dirty equipment or material and gives spirit an earthy, potato smell.]

Can refer to very different tastes, almost always defective, originating in the soil where the vine is cultivated.

We limit to these terms the naming of eaux-de-vie defects which can be innumerable. Each taster has a specific vocabulary to designate them.

Distillers who seek quality and taste often can be advised to keep samples of very good brandy. This will serve as a reference sample and will make it possible to compare the quality of the eaux-de-vie produced each year and to improve it through carefully managed distillation.

[Omitted photo of cooperative staves drying.]

Storage of the Brandy

The necessary conditions for good storage are:
—Good quality wood.

—Dry wood.
—Careful preparation of the barrel.

The most esteemed wood for aging Cognac is Limousin oak. We also use wood from theTronçais forest.

Lumber intended for staves must come from the heart of  the oak. Sapwood too loaded with soluble organic substances should be rejected, as well as wood that is too porous or too colored. As much as possible, staves should come from trees that are at least 40 to 50 years old, split and unsawn.

We will choose only the pieces devoid of sapwood and knots, without rot or worm holes, the grain will be fine and tight, the coloring fairly light and the fibers crossed by short and shiny veins; the lumber must be planed; finally, they will only be shaped after drying in a pile for the required time.

It is generally considered that the drying must last at least a number of years corresponding to the thickness of the wood evaluated in centimeters.

The barrels intended to receive the brandy must be vigorously scalded and rinsed several times with cold water. Before placing the brandy in them, you can rinse them with very clean water. Finally, 1 decalitre of brandy is introduced into it and the barrel is then vigorously shaken.

New eaux-de-vie can be housed in new barrels, but after a short time it will be preferable to transfer them to old barrels to avoid an excessive enrichment in tannins which would give astringency.

Some people boil wine in the new barrel which can introduce calcium into the brandy, because the wine contains a lot of it.

Due to the significant expansion of the eau-de-vie from increase in temperature (1), it is necessary not to completely fill the barrels: at least two liters of space must be left per hectolitre of eau-de-vie.

(1) The volume of a Cognac at temperature t is given by the approximate formula V = Vo (1 + adt)/100 in which:
a = 0.112
Vo = volume de l’eau-de-vie à 0 degré centigrade.
d = degré de l’eau-de-vie.
t = température de l’eau-de-vie.

[Omitting a photo of a cooperage.]

Mushrooms present on the walls and roofs of brandy cellars

Foreigners who come to Cognac are very surprised to see the blackish appearance of the roofs and sides of some buildings. Some parts of the city are so dark that it looks like the walls have been covered in soot. This appearance is due to a cryptogamic vegetation favored by the so-called saltpetre stone and the humidity maintained by alcoholic vapors.

This cryptogam, studied by Baudoin in 1873, had been recognized as belonging to microscopic fungi and classified it in the genus Xenodochus. In 1881, a mycologist to whom we communicated the interesting cryptogam, Mr. Dr. Richon, from Saint-Amand (Marne) definitively classified it in the genus Torula. We will not go into details on the reasons which favor of one or the other name, it is enough for us to know that the mushroom of the walls of Cognac is now “Torula Compniacensis Richon”.

This mushroom is also found in the surroundings, wherever brandy is kept and, singularly, especially where brandies are the oldest and the best.

[Omitted photo of a maturation cave.]


Maturation of Cognac. [I translate Vieillissement as maturation rather than aging.]

Cognac only acquires the qualities which have made its reputation through a prolonged stay in oak barrels.

During this stay, very apparent modifications occur: decrease in volume, change in degree, dissolution of tannin and air, concentration of secondary products, at the same time, chemical transformations that are more difficult to detect: oxidation, hydrolysis, acetilization, rancidity, etc.

Volume reduction of the eaux-de-vie:

In wooden barrels there is a continuous reduction in the volume of the liquid resulting from the slow evaporation which occurs through the walls and from the incomplete closing of the bung.

The extent of the loss depends on many factors, some internal: nature, dimensions and state of filling of the barrels: others external: temperature, ventilation, humidity of the premises.

The losses are greater in small barrels, as well as in partially full barrels.

Precise observations have shown that the losses by evaporation follow a decreasing course and that they are much more important during the first years of conservation than afterwards.

Reduction in alcoholic strength:

The influence of evaporation generally results in a reduction in the alcoholic strength because alcohol is much more volatile than water.

During aging, however, an enrichment in alcohol has sometimes been noted. (Case of very dry premises). This enrichment can occur because water passes through the walls of drums more easily than alcohol, which has a larger molecule. Under usual conditions, where the hygrometric degree is sufficient, humidity opposes the evaporation of water and not that of alcohol, so that a loss of degree is generally observed during of aging.

The measure drops by 6 to 8 degrees on average after 15 years.

Placed in a room that is too dry, the brandy decreases in volume excessively and becomes hard and dry; its degree varies little. Preserved in a cellar that is too humid, it loses a lot in degree and becomes soft: its volume varies little.

It is often admitted that wood has pores which would allow exchanges with the outside by capillary action; in reality, wood, which is colloidal in nature, swells on contact with liquid, much like gelatin and dries up on the surface in contact with the atmosphere.

Dissolution of the soluble principles of wood from staves:

Most of the soluble substances in wood and in particular those which would give too much bitterness to the brandy are eliminated by the long stay in the open air, in the rain and the sun, then by rinsing with boiling water. However, the wood after this operation still contains substances which can be dissolved slowly by the brandy which has a higher solvent power than water due to the presence of alcohol and volatile acids. [I arrived at rinsing with boiling water from l’affranchissement with can translation to liberation or postage, but which I thought may be the name of their pre-filling process.]

Coloring and odorous matters:

Quercine is a variety of resin whose smell is the main element of that of oak wood, it gives eaux-de-vie a particular aroma.

The quercitrin constitutes the principal coloring matter of the oak and imparts to the liquid a tint of a beautiful yellow old gold.

Quercitannic acid, which is the special tannin in oak, enhances the flavor of spirits while accelerating their aging.

Mineral matter:

The brandy when it comes out of the still contains no mineral matter, except copper. Due to its increase in acidity, it dissolves slowly during aging very small amounts of mineral matter contained in the wood of the barrels: Calcium, Magnesium, Manganese, Iron.

These mineral substances are not detectable in the first months after distillation; they increase with aging, all the more rapidly if the Cognac is housed in casks of more recent manufacture and of smaller capacity.

Measures of Calcium, Magnesium and Manganese originating from barrel storage, however, never exceed 1 milligram per liter. Measure of iron does not exceed 0.2 milligrams per liter.

Evolution of copper:

Copper present at the exit of the still, coming from the coil, measures at close to 2 to 3 milligrams per liter and decreases during the first years as a result of its precipitation by tannin; after a few years, this copper is redissolved as a result of the increase in acidity of the aging Cognac.

Dissolution of oxygen:

A small amount of oxygen in the air is dissolved at the separation surface between air and liquid. This dissolution is quite sensitive because alcohol is a better solvent for gases than water.

The oxygen thus dissolved does not only carry out definitive oxidations, but enters into combination with certain elements of the eaux-de-vie, for example to form unstable peroxides or intermediate oxidants which diffuse in the mass.

Gas dissolution is greater at low temperature.

Concentration in secondary products:

Some constituents of non-alcohol such as furfurol and certain higher alcohols, less volatile than alcohol, gradually become concentrated in the eau-de-vie due to the decrease in volume of the latter during aging.

Chemical reactions:


As a result of the dissolution of oxygen at the surface of the liquid, a slow oxidation of the liquid takes place, catalyzed by the aglycone fraction of the tannins which act as an intermediate oxidant. This oxidation, which relates to alcohol, the elements of non-alcohol and the tannins, gives first aldehydes, then volatile acids.

Brandy, which contains 3 to 5 grams of aldehydes per hectolitre of pure alcohol at the exit of the Still, contains around 30 grams after 20 years of aging in barrels.

Volatile acids transform from 5 grams to 150 grams per hectolitre of pure alcohol after about 20 years.

The pH of the eau-de-vie drops from 5.5 to 3.5, as a result of the dissolution of the tannins, the increase in volatile acidity and the decrease in the degree.

Oxidation is all the faster the higher the tannin content of the eau-de-vie. Oxidation is responsible for the disappearance of the boiler taste not due to Copper, but to an aldehyde compound. The oxidation takes place at low redox potential due to the presence of tannins.

With a high redox potential, oxidation involves substances which must not be oxidized, which develops undesirable tastes and odors. This explains the failure of all artificial oxidation tests on eaux-de-vie. Moreover, the role of oxidation in aging remains quite limited.

Tannins themselves oxidize slowly, lose their astringency and also give rise to fragrant products.


Aldehydes combine with alcohol to form acetals, a pleasant smelling body. The rate of acetalization is much greater than the rate of esterification. [This is a very interesting claim I had seen one 1970’s French research paper make regarding cider spirits, but I have not been able to learn more.]


It was once thought that the increase in the acidity of spirits caused a parallel increase in esters by the reaction of acids with different alcohols. In fact, the analysis does not detect an increase in esters with aging, at least in the early years. This fact can be explained by the fact that the ester formation reaction is reversible.

In reality, at the start of aging, there is hydrolysis of the esters, because these are present in the eau-de-vie in greater quantities than the corresponding acids. Molecular transpositions are carried out resulting from hydrolysis, then from esterification which relates to each ester taken in isolation and in equilibrium with the acid and the corresponding alcohol. These transformations are catalyzed by the drop in pH and by the drop in alcohol content. [Some of their observations on esters could be due to using oak that has less capacity to produce ethyl acetate than new American oak?]


Finally, there is a rancidity of the fatty substances in solution in Cognac catalyzed by the presence of copper and by the drop in pH. The effects of this rancidity become noticeable after 15 to 20 years, but are not really clear until around 30 at 40. [Quite the observation and I suspect there is a lot of speculation at a play.]

Various chemical reactions which accompany maturation are favored by the rise and variations in temperature; This is why Cognac barrels are rarely housed in underground cellars that are not very sensitive to temperature variations.

The improvement of eaux-de-vie in oak barrels does not continue indefinitely. There comes a time when they have acquired all the desirable qualities and when longer storage would not improve them appreciably. If kept longer, they would risk allowing the alcoholic strength to drop in exaggerated proportions.

It is generally observed that the maximum quality is acquired by natural aging after 40 to 50 years.

If it becomes necessary to adjust the degree of brandy, do not use water from wells or rivers that provide calcium. Rainwater stored in cement cisterns also provides calcium. Reduction must be gradual and weak with each operation. A dose of calcium greater than 5 milligrams per liter over time results in deposits in the bottles. The eaux-de-vie should never be clarified. [clarified translated from collées]

Although the general process is currently more or less known, the set of modifications undergone by eau-de-vie during maturation is very complex, essentially dependent on time, and eludes any attempt at artificial reproduction.

[I am omitting pages 121-190 which covers:
statistical numbers for production among the crus
a chapter on export figures
a chapter on the national professional bureau for Cognac
the right to the name Cognac
therapeutric value of Cognac
a primer on hydrometers
measurement of the alcholic degree of wine]

Cognac Analysis

Certain foreign countries require that French exporters enclose with their shipments a bulletin containing the Analysis of the Cognac sent.

To avoid any commercial difficulty, it would be necessary that when several laboratories analyze the same sample, they give figures close to each other. We will see the effort that has been made in this direction below.

Chemical analysis of eaux-de-vie as it is currently practiced comprises the following measures:
1 ° Determination of the degree (ethyl alcoholic % by volume).
2 ° Evaluation of “non-alcohol” which includes: volatile acids, aldehydes, furfurol, esters, higher alcohols.

Acids and ethers are determined by titrimetry, aldehydes, furfurol and higher alcohols by colorimetric comparison with standards of known content.

There was a time when we would have liked the determination of non-alcohol to inform us about the following points:
—Origin and quality of the brandy.

In a Cognac the components of non-alcohol are extremely numerous. In the usual analysis, we are satisfied with measuring them globally by “function” and by equivalence.

Thus aldehydes are evaluated as acetic aldehyde.
Ethers to acetic ether.
Acids into acetic acid.
Alcohols higher in isobutyl alcohol.

By convention, the results are expressed in grams per hectolitre of alcohol at 100°

To obtain the true composition of an eau-de-vie, it would be necessary to carry out a complete analysis by assaying each of the constituents separately.

This study was undertaken in Charente for Cognacs by Ordonneau. It represents a very long and delicate job, requiring a very large volume of brandy.

Analysis as it is currently practiced cannot provide any information on the origin (raw) because the method of distillation has almost as much influence on the chemical composition of the eau-de-vie as does its origin.

Analysis cannot provide very useful information on quality, because some substances are present in very small quantities and they are very difficult to measure, have more influence on the bouquet and taste than other bodies present in larger quantities. [The birectifier was the solution to looking at these hard to measure bodies which significantly influence aroma. Conventional distillery GCMS still misses a lot.]

However, to be of good quality, a new brandy must not contain per hectolitre of pure alcohol more than:
10 grams of aldehydes.
20 grams of volatile acids.
120 grams of ethers.

If ester content falls below 70 gr, this is an indication of poor distillation (very significant addition of water in the brouillis or excessive removal of the heads). In addition, a new brandy must not contain sulfur dioxide in any form.

The main goals of anlaysis may be:

—From a research point of view: determine for example what is the influence of modifications in distillation or vinification on the analytical composition of eaux-de-vie.
—From a legal point of view: detect falsifications or fraud.

The measure of diacetyl and acetoin make it possible to distinguish Cognac, Rum and Armagnac without tasting them.

Methyl alcohol assays make it possible to distinguish alcohols from marc or cider.

Measures of aldehydes, acetals and volatile acids give the approximate age of Cognacs.

The following figures can be cited by way of example, corresponding to the analysis of a new Cognac brandy: Real alcoholic degree at + 15 ° C. ……. 70.1 °.

Non-alcohol expressed in grams per hectolitre at 100 °:

These figures may vary depending on the origin of the wines and the method of distillation.


The official method currently still in force in France is the 1909 method. It is imprecise and insufficiently faithful.

Indeed, its wording does not sufficiently specify the operating conditions and these may vary from one laboratory to another.

In colorimetric assays, the official method does not take into account influence of temperature or that of pH. Examination of the colors is made with a visual colorimeter which is very imperfect.

For titrimetric measurements, the choice of indicators is poor.

A commission of experts has been convened to develop new methods.

The Cognac Viticultural Station has published the results of its work on modifications to be made to these methods. Many of the proposed changes have already been accepted by the expert committee All of this work will be the subject of a book which will be published in 1958 by the Station Viticole and sent to various foreign laboratories.

With these modifications the accuracy can reach 5%.

Under these conditions, it is as ridiculous to give the results with several decimal places as to give the time to the nearest second with a watch that does not have a second hand! However, we still see laboratories that have had the same sample analyzed eight days apart, which give figures with decimals that differ from each other by more than 20%!

Analyzing a sample of Cognac takes more than a day’s work. It is not possible to operate faster without precision and fidelity suffering considerably. [I’d really like to think the birectifier method combined with organoleptic analysis and selective use of automatic titration is a very major short cut.]

Some laboratories operate on samples that are too small, which also affects accuracy.

Finally, the accuracy of the analysis can in no case exceed that of the devices used, which is why recent, precise and clean equipment is essential.

Deviations should not exceed 5% for each of the “non-alcohol” elements.

In 1953, the fraud repression department established a comparison chain between laboratories. Results given by the Station Viticole de Cognac (non alcohol = 422) were the closest to those found by the Central Laboratory for the repression of fraud (non alcohol = 420), for the same Cognac. [They are mentioining this because it is the authors’ laboratory.]

Measurement of minerals:

Measurement of mineral matter in Cognacs put on the market has proved to be very useful, because the presence of mineral matter in Cognac causes cloudiness or deposits after a few months in the bottle.

Calcium for example, should not exceed the measure of 4 to 5 milligrams per liter.


[For a certain type of practicality, I have only added citations that I think will help the present day distilling community. Most would likely need to be first time digitized and translated. There are really just a few that catch my eye.]

DELAMAIN (R.). —Histoire du Cognac. Stock, 1935.
BRIAND (G.). —L’Avenir du Cognac. Conférence à la Société d’Agriculture de Charente. Janvier 1950.
LAFON (J.). — Propos sur le Cognac. Journée Vinicole. Novembre 1950.
ORDONNEAU (Ch.). —Alcools et Eaux-de-vie. Doin, 1885. [I translated this long ago but never published it. Its the first mention of Cognac oil and the unsaponifiable fraction of spirits.]
PEYNAUD (E.). —Phénomènes d’estérification dans les vins. Ann. Ferm. 1937. 242.
LAFON (R.). —La Distillation dans les Charentes. Revue de Viticulture, 1910.
THOMAS (R.). —La Distillation du Cognac. [1947]
LAFON (J.). —Dispositif avertisseur de Coupe. Annales de la Fondation Fougerat, 1938.
GUYMON (James F.). —Investigation of the influence of distillation practises upon the composition of brandy. Reprinted from Wines and Wines. Vol. 30. p. 21-24. Octobre 1949 (California).
MARILLER (Ch.). —Distillerie Agricole et Industrielle. Baillères. [I own a paperback copy.]
MARILLER (Ch.) et GROSFILEY (I.). —Le Contrôle Chimique en Distillerie. Dunod. 1939.
GRAHAM (W.-O.). —Australian Brewing and Wine J. 58 (6). 40, 1940.
JOSLYN (W.A.). and AMERINE M.A. —”Commercial Production of Brandies” California Agr. Exp. Sta Bull 652. p. 14 (1941).
VALEAR (P.). —Ind. eng Chem. 31. 339 (1939).
LAFON (R.). —Les pourritures des raisins dans les Charentes. 1950.
LAFON (J.) et COUILLAUD (P.). —Sur la présence du cuivre dans les eaux-de-vie de Cognac. Annales de Technologie de l’INRA. I. 1953.
MICKO (K.). —Zur Kenntnis der Untersuchung von branntweinen Unters Nahr Genn. [Start here]
KERVEGANT. —Rhums et Eaux-de-vie de Cannes. Les Editions du Golfe, Vannes, 1946.

[Reminder to me to read this:]

We would like to thank Mr. HUDE who drew all the graphics contained in this book.

5 thoughts on “Le Cognac by R. Lafon, J. Lafon and P. Couillaud (1958)

  1. Love the amount of actionable, practical insight in this one. Clearly, written from the perspective of an active producer.

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