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This is a minor first hand account of Jamaica rum production. I chose to highlight it because it features some unusual ideas for starting the season that are described in later years by other authors. Feel free to breeze through it and find my notes in bold.
MAKING AND DISTILLING OF RUM
Cleanliness is a principal means to produce not only good but large quantities of rum. For this purpose every vessel which is to be made use of in its manufacture should be kept as clean as the nature of things will admit. The skimming molasses dunder mixing and fermenting cisterns should all be well cleared out preparatory to a rum crop. Even the tank should have its share of attention in that respect the stills be brightly scoured inside and the worms forced with water to discharge any scum mud crustated stuff or other matter which may obstruct the free passage of the distilling liquor or adulterate it. [Never in the literature do we see this kind of attention giving to cleaning the still. I don’t think its common knowledge what current practices are.] It is sometimes difficult in the commencement of a rum crop, (when the distilling house is cold from disuse,) to bring on free, quick, and strong fermentation in the liquor, after it is compounded. It will be requisite in order to promote this essential property to bring into action something to assist its natural efforts. The fermenting cisterns should be well cleaned and dryed out then filled with some green mill trash, which has not been much squeezed, that the fermentation arising from it may sweat and warm the cisterns. This trash should remain in them covered up till they are wanted to be filled with liquor from the mixing cistern. [This is an absolutely fascinating folk microbiology idea I haven’t not seen described anywhere until the 1882 Vale Royal paper puts rum cane mill trash in their mixing cistern.] The house should have a fire made in it so central that the warmth of it will diffuse through it and dispel the chilly cold dampness of the fermenting part of the house. [Warming the fermenting room was described by Burton in 1875.] The liquor should be compounded (the first round of the fermenting cisterns) rather lightly of heavy sweets, so as to induce by its volatile light quality quick fermentation and that in two or three rounds of the house by gradually strengthening the liquor with strong heavy sweets, the standard of fermentation may be critically fixed to answer the disposition of the house in yielding good returns from the liquor. The house being thus regulated nothing is wanted but cleanliness economy and a due share of sweets from the boiling and curing houses to give an adequate return of rum to the number of hogsheads of sugar made that is one half the number of puncheons of rum to the number of hogsheads of sugar which if produced is a criterion to judge by that the distilling house department has been managed with attention and ability. But a parsimonious conduct in the affairs of the boiling-house, may quash an impartial crop in the distilling house and render both crops poor and unproductive.
No old dunder (or wash from the liquor still) from a former crop, should be made use of to mix with liquor of a new crop. This pernicious stale stuff, should be thrown away and the dunder cistern left empty to receive the new dunder from the first liquor that is distilled; good fresh clarified dunder is an ingredient when given in right proportion, which will enhance the strength and fermentation of the liquor; but if of a weak muddy and bitterly sour nature it will ruin all the other ingredients retard fermentation, make it work heavy, take a long time to ripen, and give poor returns. If the skimmings have not been purged from spume and dross, and in a manner clarified previous to being mixed with the liquor preparing for fermentation, they will cause the liquor to be ropey [Leucanostoc bacteria], work heavy, be slow in fermenting, vapid, and produce small returns; it then behoves a person superintending the distilling house to be nice and exact as to good clean dunder and skimmings.
Twelve per cent sweets will be high enough to set the liquor in the beginning of a distilling house crop; but when the house is warm with good strong fresh dunder to make use of and powerful fermentation pervading all the cisterns, I would set the liquor as high as fourteen, or fifteen per cent of sweets. A measuring rod is a useful implement to ascertain the quantity of each ingredient. This may be put into the mixing cistern with a per centage scale scribed upon it, equal to the depth of the mixing cistern; so that if the mixing cistern holds twelve hundred gallons this rod should be marked with twelve cross scribes and the space between each scribe divided by ten nicks; each scribe denoting one hundred gallons and each nick ten gallons. The skimmings and dunder having been in some measure clarified, this twelve hundred gallon mixing cistern I would proceed to fill with its compounding ingredients at fourteen per cent sweets; that is, one hundred and sixty eight gallons of heavy sweets or molasses; taking it for granted, that every eighty gallons of good skimmings is equal to one gallon of molasses. I would have turned into the cistern four hundred and eight gallons of skimmings which is equal to sixty gallons of molasses. It then requires one hundred and eight gallons of molasses to make up the complement of sweets which should be likewise thrown into the cistern. Having its proportion of sweets and being filled up to five hundred and eighty eight gallons with skimmings and molasses; that is forty per cent on the measuring rod of skimmings and nine per cent of molasses; the cistern now wants six hundred and twelve gallons of liquid to complete it. I would then add, for this purpose, four hundred and thirty two gallons of dunder, and one hundred and eighty gallons of pure cold soft water; that is thirty six per cent of dunder and fifteen per cent of water on the measuring rod. Total, twelve hundred gallons being the contents of the mixing cistern and mixed at the rate of fourteen per cent of sweets. This liquor so composed should be well stirred up and commixed, by a perforated broad board, placed to a well fixed staff or handle. The liquor must then be left to rest, till it begins to ferment. The foul drossy head should be skimmed off it, and the fermenting cisterns being ready for its reception, it should be pumped or allowed to run into them till they are full. In this manner should liquor be set in the height of crop. The liquor when it is passed into the fermenting cisterns, must be kept clean by a skimmer; when no skimmings are to be had, the full quantum of molasses must be mixed at the rate of fourteen per cent; that is one hundred and sixty eight gallons of molasses, with fifty per cent of good pure dunder, or six hundred gallons of it; making together with the molasses seven hundred and sixty eight gallons. The cistern must be filled up with pure cold soft water, and will require four hundred and thirty two gallons at the rate of thirty six per cent on the measuring rod, making a total of twelve hundred gallons, being the contents of the mixing cistern, comprising fourteen per cent molasses, fifty per cent dunder, and thirty six per cent water. [These numbers for some reason imply no volume held back to start the next ferment which possibly did not become a universal practice until alter.] When beginning to ferment, it should be skimmed and then pumped or passed to the fermenting cisterns. In this manner should the house be set round with liquor. When the fermentation subsides, or ceases in the fermenting cisterns, the liquor is ripe for distilling, which may be known by whitish bead-like particles, or small globules appearing on the surface of the liquor, or a thin white surface shewing itself on it [My best guess is that a common mycoderma grows on the surface at the end of fermentation as more oxygen reaches the surface.]. There should no time be lost in distilling it. It should be passed into the low wine still, the still well closed, and a strong fire put under it, till the low wine begins to run slowly from the worm [This descriptions implies no retorts.]. A moderate fire must be kept up, till the low wine is run off. According as the fermenting cisterns are emptied, they should be washed out with warm water, and filled immediately again, so that the fermenting spirit may be retained in them.
Good strong liquor should give a fifth from the still in low wines. Care should be taken to run off the low wines cool from the worm, and no liquor allowed (by the strong a fire being made under the still) to descend with it, through the worm. When there is enough low wine made to fill the rum still, or a couple of hundred gallons more, it should be passed into it, the still well closed up, and a quick strong fire made a under it, till the rum begins to trickle from the worms. Then most of the fire should be damped or withdrawn, and the rum suffered to run cool from the worm. Good low wine will give one-third strong rum, or rather more. Plenty of water should be running into the tank, to keep the worms cool, and the surplus warm water, which rises to the surface of the tank, should be let off by a proper outlet. Neither the low wine or rum still should be filled higher than within six or eight inches of the rim of the still, that no accidents may take place by explosion, or any of the liquor or low wine from the stills, be suffered to pass down the worms to contaminate the distilling liquor. The still heads and goose necks, must always be well closed and secured, whenever the stills are loaded with liquor or low wines, and a brisk strong fire made under the stills to bring them down, or make sufficient ebullition by boiling. After this, moderate fires will work off the distilling liquor. For the purpose of preserving good dunder to mix the liquor with, the entire spirit from the liquor still, (or rather low wine still,) should not be run off the still, but a few distill-house cans retained in the still, of the last runnings of the low wines, so that the dunder may be strong, and kept fresh and good, to mix in subsequent liquor, which it much enhances the strength and fermentation of [This idea of not exhausting the dunder of volatile acid seems very contrary to what comes later in the common clean process]. When running off, or distilling rum, a proof bottle should be kept, into which (by a phial containing a certain small quantity) a portion of the rum, from each distilling house rum can should be put; and when the rum so put into the proof bottle comes to the mean standard of twenty two strong proof by a London or Glasgow proof bead, the remainder of the spirit, which comes from the still worm, should be thrown up into the low wine butt [I can’t quite tell if the proof bottle is a pycnometer or just a graduated cylinder to float a proof bead which is likely a philosophical bubble. 22 over proof is 69.71% ABV. However, the logic here is funny and another paper of the same era claims they used bubble no. 22 which was 15 overproof which would be 65.71% ABV.]. Any more mixture of it in the rum, will both make it weak and give it a bad taste and flavour. Every week the stills should be completely scoured, and every time they are filled they should be well washed out with water. The dunder and skimming cisterns should be cleaned out every week or fortnight.