Distillery Practice—Gin

Follow along: IG @birectifier

A very unique mimeographed manuscript crossed my desk that was written by a Seagram employee, likely in the late 1930’s or early 1940’s, but before the famous 1943 Seagram text called “Fundamentals of Distillery Practice” written by Herman F Willkie and Joseph A. Prochaska. I’m not aware of any informally published manuscript like this having been found by the distilling field. It came to me from an individual who wanted to contribute to the education of the new generation of distillers.

The manuscript is a bit scattershot and not exactly in any kind of order and contains a ton of information from the era not seen in the 1943 text. This was likely intended as an internal training document. These were the kinds of jobs where once you were in, you were in for life so they took education seriously.

I’m currently overwhelmed with material after recovering two other lost texts so what I’m choosing to cover first are the writings on gin in the manuscript. No author’s name is attached to the document, but it is very likely Herman Willkie based upon another gin tell all he wrote in 1937 for Hiram Walker. Willkie also wrote yet another document which details all their analysis methods and I have explored most of them over the years because they are still extremely practical for standardizing a botanical charge. I have also widely explored both gin and single botanicals with the birectifier which has yielded a lot of insights. The birectifier may be just as valuable for gin as it is for any other spirit type. Gins can be compared to industry leading role models, and, by evaluating the fractions, courses of action can be taken to make a new product better match the proportions of industry leaders. Over years of evaluating new gins as a restaurant buyer, its very plain that few new American distillers achieve the control over their botanicals that they want.

Seagram gin has always been a favorite of mine, mainly for its affordability and I always keep it around. It is among the very best selling gins of the world, yet contemporary opinions do not regard it highly. Few people know that it was a technical marvel for being distilled under partial vacuum (and a few other industry leaders are today as well), but at the same time we do not know the state of the historic equipment or if it was ever abandoned for cheaper methods because it is likely produced at multiple locations for the global market. Does the current product stand as it will be described below?

Reading what follows, I got the feeling we are in the shadow of a lost civilization. These ideas are over 80 years old yet most gin distilleries are incapable of matching the technical achievement today. Diageo currently owns Seagram gin and if the vacuum stills are still intact and with spare process time, it would be great to see them explore some new ideas to honor the modernist spirit of its founding.

Gin -41

Distilled dry gin in made by redistilling grain neutral spirits over or with various aromatic botanicals. Essentially then, the process is one of extraction and distillation. The essential oils, which are extracted from the botanicals by the alcohol solution, give the gin its characteristic flavor and odor. Only grain spirits of highest purity should be used and the quality of the botanicals or gin ingredients should be of the best.

Gin Ingredients

Our specifications covering gin botanicals prescribes the age, best harvesting season, and the countries from which acceptable botanicals are grown. Maximum limits and minimum requirements for moisture, percentage of essential oil, acidity, specific gravity and refractive index of oil, and any other factors indicative of quality are specified. Only those botanicals meeting these specifications are purchased.

Central Storage Chambers

The proper ingredients are held at a low temperature and controlled humidity until ready for use. This prevents deterioration of the ingredients due to high temperatures with the resulting loss in potency. When an order is received from one of the plants, the proper ingredients are weighed, proportioned as to formula, and packaged in tight containers for shipment to the plants requiring them.


Gin distillation is usually carried out in a kettle with a copper vapor line leading to a condenser. The heat is supplied to the kettle indirectly, by steam condensing in a coil within the kettle. Sometimes the vapors pass through a column fitted with baffle plates before reaching the condenser. In this case some of the distillate may be returned to the column as reflux.

Recently the importance of distilling at a low temperature has come to be realized. The low temperature is the result of vacuum distillation. The essential oils are not all stable at higher temperatures and part of the oil is broken down resulting in the formation of some harmful constituents. The vacuum still is the answer to this problem.

Vacuum Gin Still

The vacuum gin unit consists of a pot, flash chamber, column, partial condenser, total condenser, calandria and ejector condenser. The pot is under atmospheric pressure while the flash chamber, column and both condensers operate under reduced pressure.

Gin Pot

The grain neutral spirits and gin ingredients are charged into the pot and recirculated by pumping from the pot through the calandria into the flash chamber and back again to the pot. This recirculation of spirits and gin ingredients is maintained until the run is completed.


The purpose of the calandria is to supply indirect heat to the grain neutral spirits and gin ingredients mixture before reaching the flash chamber.

Flash Chamber

The heated material from the pot, which is at atmospheric pressure, flashes on reaching the flash chamber due to the low pressure within this chamber. The portion which is not vaporized flows back to the pot while the vapors continue into the column.

[What seems quite special about using a flash chamber is that you only have to keep a much small volume under vacuum so you may not have to physically reinforce as much of the unit. I’m not sure if a partial vacuum pot still such as just installed at Foursquare uses the same principle.]


The vapors from the flash chamber feed into the column. The purpose of this column is to achieve enrichment of the gin distillate.

Partial Condenser

Part of the vapors from the column are condensed in this dephlegmator and returned to the column as reflux.

Total Condenser

The vapor leaving the partial condenser is completely condensed in the total condenser. Part of the condensate is returned to the column as reflux and the remainder flows to the gin tank as finished gin.

Distillation Factors

During the distillation the proof of the distillate is held constant until the very end of the run when tails are withdrawn. The steam to the calandria, vacuum, and condenser cooling water are also held constant while the reflux is varied in order to maintain a constant proof. Steam, vacuum, specific gravity of distillate,and condenser cooling water are regulated by automatic controls.

Indicating and Recording Instruments—The indicating and recording instruments used are:
Temperature—Thermometers, recorders
Vacuum—Gauges, manometers
Specific Gravity—Hydrometers, recorders
Flow of Fluids—Rotameters

Somehow this section abruptly ends and we end up at a section in the last pages of the manuscript titled: Gin.


No other beverage in all history is surrounded with an exotic a story as gin. No other distilled beverage may lay claim to a more interesting history, entwining its various roots in the rise and fall of empires; in the emergence of the dominant mercantile classes of the seventeenth and eighteenth century; in the history of medicine; the voyages of exploration, adventure, and conquest. The pages of history are colored with the deeds of explorers who were searching for new sources of spices and botanicals which were to be used for many purposes, varying from condiments to perfume, from incense to the making of gin and liqueurs. It is in the latter usage that our field of interest lies.

Gin consumption was increased during the “dry era” because bootleg gin was comparatively easy to make, whereas the production of our present high quality gin requires a great deal of skill and experience. During prohibition anyone who could obtain some potable ethyl alcohol and some gin essence could make “gin” by simply mixing the ingredients in a vessel. Gin has a pleasing odor and taste which delighted the hearts of a beverage-starved public. Also, gin requires no aging and may be consumed immediately after its preparation. Much of the prohibition popularity of gin was due to the fact that it was an inexpensive beverage.

On the other hand, gin was considerably maligned during this period. The poor quality ingredients used; the spurious and adulterated “gin drops” which were widely peddled on drug, grocery, and cigar counters; the inexperience of the “compounder”; the poor quality alcohol obtainable; and similar factors resulted in the production of low grade, bad tasting, and ill-smelling gins. For this reason gin achieved a wide-spread reputation in this country for being primarily a “mixing” drink, to be consumed only in connection with other better tasting and more pleasant smelling ingredients.

“Bathtub gin” generally deserved its poor reputation. Gin prepared, however, under modern industrial process conditions and under the supervision of a skilled expert is a fragrant, palatable, smooth beverage which is held in high esteem by connoisseurs all over the world. On the continent and in the British isles it is a favorite beverage not only for “mixing” purposes, but also as a “straight drink”. When mixed, the aim is not to disguise or hide is flavor and bouquet, but rather to enhance and blend it with the other ingredients used. Both “English” and “Holland” gins have a well rounded flavor of a definite character. They are smooth, aromatic, and pleasant tasting, and they differ characteristically from one another.

Gin is in use in almost ever country in the world. Not only does its wide-spread usage lend it an international air, but it achieves its unique distinction as a cosmopolitan drink by virtue of the fact that it is the product of many climes and many peoples.

The origin of gin is generally traced back to “juniper wine”. Gin itself was invented by a Dutch professor of medicine, who considered his new find as a medicine and not a beverage.

The history of gin production may be divided into three periods, each of which is marked by a significant development in the methods of manufacture. The first period may be termed the pot-still era. The gin of this time was produced from spirits obtained by a simple distillation, without rectification, of a grain mash. The flavoring ingredients were added to the “spirits” as essences or concentrates after the distillation. Such a gin was truly a “hard” liquor as it was produced from unrefined spirits. The production was heavy-bodied and carried all of the congeners and grain flavor which we now commonly associate with whiskey.

The invention of the patent still brought about the second era in gin history. Such a still—the forerunner of the continuous multiple column spirit still—made possible the production of a spirit which has undergone some rectification and refinement. Whereas the previous gin makers simply mixed this spirits with the botanical oil and essences, with the introduction of a relatively neutral spirit, gin production turned to the re-distillation and rectification of the alcohol or spirits directly in contact with or through the botanicals . This second era represents the transition from a simple mixed gin to a distilled gin wherein the flavoring is fused into the spirits by distillation.

The third period in the story of gin manufacture which may be termed the modern era, is comparatively recent and is represented by the developments with our own company. Its distinction lies in the application of intensive chemical engineering and botanical knowledge to the manufacture of gin instead of the rule-of-thumb methods, steeped in tradition, that were formerly used.

Gin may be classified into two primary categories, namely, a compound gin an distilled gin. Compound gin is made by simply adding mixtures of essential oils, essences or flavorings to neutral grain spirits which have been diluted to the desired proof. Distilled gin is the distillate obtained by an original distillation or re-distillation of neutral spirits over or with the juniper berries and other aromatic botanicals customarily used in the production of gin, deriving its main characteristic flavor from the juniper berries, and being reduced at the time of bottling to not less than 80° proof.

In general, gin may be defined as an alcoholic beverage flavored with the volatile products of juniper berries and other aromatic herbs.

In the preparation of a distilled gin the various flavors tend to fuse with one another, producing a more homogeneous product than can be obtained by the mere mixing of ingredients. When both botanicals and alcohol are distilled together in the same vessel there is an interaction between the flavoring elements resulting in the formation of a flavor and bouquet which are finer than can be obtained by a simple mixing of the essential oils and alcohol.

Distilled gin may be further classified as Holland or Geneva gin and English or London Gin. These variations are primarily in the character of the grain spirits which is used. In Holland, gin producers prefer a spirit obtained as the distillate of pot-still operation. Consequently, this spirit has a much higher congeneric content than that obtained from the improved continuous multiple column spirit still. Also, much of that grain flavor is carried over into the gin. These Holland spirits are very similar to spirits which American practice would designate as raw or immature whiskey.

Most American gins are of the English or London type which utilize a neutral grain spirit. The spirits thus obtained, containing a minimum of congeners, are practically neutral. As a result, the flavoring of London gin depends almost entirely upon the quality and quantity of botanicals used, and upon the technique of distilling the spirits and botanicals together.

The principal botanicals used in gin flavoring are: Juniper berries, Coriander seed, Orange peel, Angelica root, Lemon peel, Orris root, and Cassia bark. Other ingredients are sometimes used according to the type and formula of the gin to be made. The botanicals used in Seagram’s gins are gathered from all parts of the earth and relatively few are obtained domestically because of the quality standards set by our specifications, as well as the fact that many of these botanicals are not native to this country.

The juniper berries are obtained principally from the region of the Apennine mountains of Italy and must be of the immediate past harvest. The juniper bush is a small evergreen. The berries are 8-10mm. in diameter and are of a steel blue color.

Coriander seed is obtained from Hungary, Russia, Germany, and England and must be of the last harvest before sale. The best harvesting season is in August. The coriander is a plant of the parsley family having aromatic seeds about 1/8 inch in diameter.

Orange peel used in gin flavoring is obtained from Spain. The peel is of the sweet Spanish type. The most desirable harvesting time is during December and April. The peel is processed in England before shipment to this country.

The Angelica root comes from Saxony, Germany. The maximum permissible age of the root is one year and a spring harvest is preferable, though the root is harvested in September and October as well as April. Angelica is a small plant of the parsley family. The roots of the plant are air dried and used as a gin ingredient.

Lemon peel is obtained from Sicily and Calabria. The fall harvest of November is desired as the fruit should not be too ripe. The Sicilian lemon peel is processed in England before shipment to this country.

The orris root is obtained primarily from Florence, Italy. The orris is a small plant of the iris family. The orris root used in gin making is a mixture of several of the iris plants which are harvested in August of the second or third year after planting. The aroma is developed during the drying process. The roots are 4 to 10 cm. in length and of a whitish color.

Cassia bark is obtained from a Chinese cinnamon tree. The cassia is and evergreen tree, native of Southern China and yields a desirable bark for aromatics when about ten years old. The tree is cut into pieces of convenient length and the bark stripped off. After 24 hours of drying the epidermis is scrapped off. Upon further drying the strips of bark are tied into bundles for export.

Today we know that the various volatile constituents and extracts derived from the botanicals are the factors which communicate to gin its flavor, character, and bouquet. Consequently, if we are to arrive at uniformity, consistency, and standardization, it is necessary that a regulated quantity of each botanical be added in each distillation so as to insure obtaining a specified quantity of oil essence, flavor, and bouquet. Another necessity is assurance that the character of these essences be the same.

Accurate standards are therefore needed for determining the quantity and quality of volatile oils and other constituents present in the botanicals. Quantity alone is not sufficient but must be augmented by carefully determined scientific quantitative standards and analysis of the materials being used. In this way we can be sure that the variations in oil and flavor concentrations existing in different botanicals from year to year can be compensated for. This is most essential in botanicals from different geographical and climatic areas, since they often vary widely in type, quality, and the quantity of flavoring and other volatile constituents.

The essential oil values, flavor values, etc. change under different storage conditions. The age of the botanicals, the size of the seed or root, the period of time expiring since harvesting, the temperature, humidity, and air circulation of the botanicals; consequently proper storage of the botanicals is as important as their careful selection.

Botanicals which are not immediately used should, upon arrival from the diverse corners of the globe, be stored in specially constructed rooms which can be kept free of insects and rodents. The temperature of such rooms must be comparatively low, since excessive heat tends to accelerate evaporation as well as promote the loss of some of the highly volatile oils. Light rays generally effect botanicals undesirably and should be minimized. Humidity is still another factor which requires careful regulation varying with different botanicals.

The gin ingredient storage rooms were designed to inhibit the deterioration and loss of essential oils. All wall, ceiling, and column surfaces of the room are cork insulated, and refrigeration doors covers all entrances. Thermostats and humidostats of an automatic air conditioning system keep the temperature at 48° F. and the relative humidity at 65%. The botanical containers are stored on ventilating stands to allow adequate air circulation. There are no windows in the storage rooms so that the effect of light upon botanicals is reduced to a minimum. The botanicals are purchased in relatively large quantities to avoid quality variations in shipments. Also, a uniform supply of ingredients may be maintained to insure a constant quality of gin.

From the ingredient storage room, batches of mixed botanicals are prepared according to formulae and shipped in moisture proof double wall containers to the gin production centers. These carefully weighed and labelled batches are prepared only as gin production needs dictate. At the gin production plants, a prescribed number of proof gallons of grain neutral spirits are redistilled in contact with each batch of botanicals.

Before large scale distillation of any compensated formula is attempted, a trial distillation is made on a laboratory pilot still. The various ratios of the botanicals to the grain neutral spirits are adjusted in this trial in accordance with the determination of the flavor values of the botanicals, thus the test serves as a check on the correctness of the compensated formulae. Also, adverse reactions between botanicals can be determined and eliminated in advanced of actual production.

In the atmospheric gin still for the manufacture of gin the grain neutral spirits are charged into the gin kettle. The neutral spirit is the product of the vacuum spirits still and is practically free of congeners. The charge consists of spirits reduced with distilled water to 125° proof and an amount of ingredients dependent upon the type of gin and formula which is being observed.

The kettle is heated by means of enclosed steam coils. The rising vapors pass up from the kettle through an attached gin head, which is simply a vertical partial condenser situated above the kettle and may use air or water as the cooling medium. This gin head condenses the higher boiling constituents of the rising vapors and permits the lower boiling or less harsh components to pass on to a final condenser. All of the vapors passing through the gin head are condensed in the condenser and flow through a tail box. From the tail box the product may be diverted to the heads tank, to the gin storage, or back to the kettle.

At the start of the run all of the final product through the tail box is returned to the kettle and the charge is boiled at a low rate for a period of several hours, again depending upon the formulae being used. During this period the ingredients are quite well “steeped” with the spirits and we are ready to distill over a gin product. The flow from the tail box is then diverted to the gin storage tank in the wine room and the gin distills at about 175-185° proof at a gradually increasing rate throughout the run. The temperature of the vapors rising to the final condenser is from about 170° F. at the start of the run to 190° F. when the flow of product is diverted to tails and the still kept in operation until the proof of the product is practically zero.

The rate of flow of product is varied or controlled by varying the amount of steam to the heating coils. The temperature at any point in the system varies from 170° F. to 212° F.

The vacuum gin still represents a successful attempt to produce a high-quality gin at low distillation temperatures. With atmospheric distillation and the accompanying high temperatures of 170-212° there is danger of overheating the ingredients and also producing a harshly flavored gin. At these temperatures there may be decomposition of the essential oils as well as the organic non-oil portion of the botanicals to produce undesirable flavors. By operating a still under reduced pressure, lower operating temperatures are obtained. The vacuum gin still now in use and the similar stills to be installed are designed for the purpose of producing a gin which is devoid of the ill-flavored decomposition products of the atmospheric distillation.

With a vacuum still as with the atmospheric stills, the heads and tails of the distillation are separated from the middle cut as undesirable. The spirits of the heads and tails are recovered, the flavor removed by a recovery process, the heads and tails redistilled, and the product, called “Residue”, recharged to the vacuum gin still as 6% of the total spirit charge.

The other 94% of the spirit charge is high quality, 192 proof spirits from the Vulcan still. This spirit charge is reduced to 80° proof with distilled water before distillation is started. [Plant scale vacuum continuous distillation may have bee invented by Vulcan in 1937. Keep in mind, gin distillation is a batch process.]

The entire charge is placed in the charging vessel and circulated through a calandria, which is heated with desuperheated steam at a temperature of 200° F., and into the still which is under an applied vacuum of 29.5″ Hg., then back to the kettle. The still and calandria are both over 35 ft. above the charge kettle, so that with the connecting pipes filled with liquid and forced circulation the liquid passes into an area of applied vacuum and back to the kettle. The vacuum is maintained on the still as the connecting pipes to the kettle act as barometric legs [essentially a condensate drain]. A small six-plate bubble-cap rectifying column provided with a reflux feed at the top plate is located over the still. This permits regulation of the proof of the draw-off by control of the reflux. The gin is totally condensed in a water cooled tubular condenser and divides into reflux and draw-off. Control is entirely by a valve in the draw-off line, the gin which is not drawn off being returned as reflux. Valves in the reflux line are kept wide open. An automatic valve is located in the draw-off line actuated by the difference in the specific gravity of the gin product and water. These specific gravity legs are maintained in a water bath at 60° F., the standard temperature for proof measurement. Thus the draw-off is automatically controlled to maintain a proof of 170°. The operating temperature  in the system is never above 125°F. As compared to 212°F. of the atmospheric gin stills. Consequently, a soft and smooth gin devoid of all harsh or high boiling ingredients, and decomposition products is obtained.

We are now, by virtue of the technical developments within our company, at the most advanced period of gin manufacturing. Though the history of gin is filled with intrigue and adventure it has now reached the time of scientific control. As pointed out, by means of careful selection and care of the botanicals we can now create any desired gin with complete assurance and faith that the product will be as desired.

Gin still maintains its aura of romance because of the amazing technological developments taking place within the industry at the present time and the advances being made in the improvement of the beverage by our research department. Each ingredient is selected according to prescribed standards instead of the senses of some adventurous sailor. The proportioning of the aromatic herbs and berries to any lot of gin is definitely controlled instead of estimated by a compounder who bases their procedure upon empirical methods.

The development of the reduced pressure distillation of gin represents a decided forward step in the production of a smooth gin of high quality. The lower operating temperatures which are maintained in the operation of the vacuum still permits a product which is free of the decomposition products usually obtained in ordinary atmospheric distillation of gin.


Relative amounts of ingredients composing the various gin formulae. [My guess is the first data set describes formulas Seagram acquired by acquisitions while the second is what Seagram uses for their basic gin.]

Ingredients   /   Lbs./1000 W.G. [Numbers are given but I’m withholding them.]
Juniper berries
Coriander seed
Orange peel
Lemon peel
Angelica root
Cassia bark
Orris root
Calamus root
Licorice root
Bitter orange peel
Anise seed
Caraway seed
Fennel seed
Celery seed
Dill seed
Cardamom seed

A standard type of gin formula (pounds of ingredients per charge of 3,000 wine gallons at 100° proof)
Ingredients    /    Pounds [Numbers are given but I’m withholding them.]
Juniper berries
Coriander seed
Cassia bark
Angelica root
Orange peel
Lemon peel

3 thoughts on “Distillery Practice—Gin

  1. Does anyone understand the “tail box” technic?
    “The kettle is heated by means of enclosed steam coils. The rising vapors pass up from the kettle through an attached gin head, which is simply a vertical partial condenser situated above the kettle and may use air or water as the cooling medium. This gin head condenses the higher boiling constituents of the rising vapors and permits the lower boiling or less harsh components to pass on to a final condenser. All of the vapors passing through the gin head are condensed in the condenser and flow through a tail box. From the tail box the product may be diverted to the heads tank, to the gin storage, or back to the kettle.

    At the start of the run all of the final product through the tail box is returned to the kettle and the charge is boiled at a low rate for a period of several hours, again depending upon the formulae being used. During this period the ingredients are quite well “steeped” with the spirits and we are ready to distill over a gin product. The flow from the tail box is then diverted to the gin storage tank in the wine room and the gin distills at about 175-185° proof at a gradually increasing rate throughout the run. The temperature of the vapors rising to the final condenser is from about 170° F. at the start of the run to 190° F. when the flow of product is diverted to tails and the still kept in operation until the proof of the product is practically zero.”

    The schema can be seen on the Controlling Gin flavor document here : https://www.bostonapothecary.com/birectifier-analysis-of-a-historic-gin/

    I never read that before. What mean’s “all of the final product”? Does he means to distill in a sort of “closed circuit” for a time?

  2. Hi Simon,
    I believe they are inserting a rectifying step into their process because they are dealing with unrectified spirit that may be high in aldehydes. They boil under high reflux with the aid of water jacketing their “gin head” which is a temporary source of high reflux, then they stack up volatiles in their column and draw them off as heads. They continue distilling and turn off that temporary reflux, running the next amount of distillate back to the pot as things come to a new equilibrium, then they proceed with fairly conventional gin distilling.

    So I think the tail box is just a liquid routing mechanism and the closed circuit is only used as the apparatus is coming to a new equilibrium which probably takes a while at that scale.

    Some large scale, economy oriented, gin stills had two gin baskets where one was used and the other bypassed so it could be reloaded and the process kept running.

  3. Thanks for the reply! Yes for a large scale it makes sense.

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