Scientific Control of a Rum Distillery by F. I. Scard

This great (possibly 1916) article from the International Sugar Journal by F. I. Scard immediately brings up some themes I’ve been talking about in distillation. For starters, Scard was a name who criticized the Veley’s in their debacle over the micro organism of faulty rum 91898). Remember the punchline?—the organism might simply have been decomposed raw meat! And the hint comes from a comment by IRS researcher extraordinaire, Peter Valaer in 1937.

The idea I’m promoting is that just like fine wine did not exist without the lab, the same is true for spirits. The winners of the judgement of Paris were all lab guys and the same will be true for great distillers past and future, skipping the present.

In the case of a rum distillery the position is very different. It is not the sucrose alone which has to be accounted for in the course of manufacture, but all the formentable sugars, glucose, and invert sugar, as well as sucrose, which find their way to the distillery. The object of the operations of a distillery is not to separate and obtain these sugars as such, but as a product formed from them by biological means before its actual separation by distillation, a product in which the flavour is a vital point in its value. The microscope thus plays an important part in the control of a distillery.

Here we have language that sums up chemical and biological control and shows conscientiousness. The science goes on to get very heavy and shows that people of PhD level science education were involved in the production of fine rums. After much heavy duty science wanking Scard puts a time stamp on a known technique for making fine rums:

It sometimes happens that the wash is not sot up all at once, but that fermentation is allowed, purposely, to start before the set is completed, being gradually fed with “sweets” until the desired charge is obtained. In this case the constituents of the wash must be measured separately, and the sweets determined separately too.

Incremental feeding of washes was a technique further elaborated years later by Arroyo and may be unique to rum fermentations. He does later go on to criticize the technique possibly because it does not fit neatly into his idea of control.

As already mentioned, the microscope plays an important part in the control of the fermenting loft. The great enemy to fermentation is the putrefactive, bacillus and the wash requires to be constantly examined for the presence of these organism. A few are invariably present, but, if the condition of the wash is favourable to their development, the yeast plant is soon smothered, and there is nothing else to be done but to clean up the distillery in every detail. It is as well also to keep a microscopic eye on the yeast plant, to see if it is developing properly, and at the same time to look out for moulds or other organisms inimical to the yield of alcohol.

Oh, maybe we are not talking about fine rum here after all, but rather the commodity category? Fine products require a certain philosophy where control isn’t sought completely, but rather just enough control to frame windows for chaos. Arroyo later showed us the benefits of controlled putrefactive fermentation and aroma beneficial moulds. The rums of Hampden estates go on to tell a very singular story where they break all the rules and there is certainly no one going around “cleaning up the distillery in every detail.”

The number of gallons going to the still in the form of wash during the week is recorded, together with the amount of alcohol received from it. These should agree within 5 per cent, with a pot still and 1 per cent, with a continuous still. The lees, or spent wash, should also be examined for alcohol by distillation, daily in the case of a continuous still, and from every distillation with a pot still, to see if any alcohol is escaping in this way. 250 c.c. should be taken and 50 c.c. distilled off, the gravity of which is taken with a specific gravity bottle, and corrected for temperature, when any loss of alcohol will be at once discovered.

This test can be run with a profit motive, but if you put in the time, you’ll also learn about lost aroma. With a flipped motive, fine rums can benefit from many of the same protocols as commodity rums.

In order to ascertain the amount of spirit obscured, the following is a reliable and simple method, and preferable to the distillation method in the case of strong spirits like rum. The specific gravity of the coloured spirit is taken in a specific gravity bottle, or by Sikes’ tables, if the Sikes’ hydrometer is used. 100 c.c. are then taken and evaporated until all the spirit has been driven off, i.e., when the residue has reached a syrupy consistency. The residue is now dissolved in water, and made up accurately to 100 c.c. at the same temperature at which the gravity of the coloured spirit was obtained. The specific gravity is now taken. The decimal part of the gravity is then subtracted from the gravity of the coloured spirit, the remainder giving tho gravity of the spirit without the colour. From this gravity the quantity of alcohol present can be obtained by reference to tables.

Currently the TTB requires the distillation version of the test, but the version presented by Scard (and arrived at my myself independently years ago for studying liqueurs) is remarkably easy and with modern day instruments can be performed on remarkably small scales with amazing accuracy. Small, 5mL, volumes of historic rums could be sacrificed to get this data. There is huge criticism of obscuration in the rum world and yet no leading authority has been sophisticated enough to perform this test for themselves. From 5mL-10mL samples, and a collection of bottles, it would take very little from the rum community to look at the obscuration changes in many brands over recent history. If consumers feel obscuration is important to the fine rum category then here you go.

Faults in rum are found by the following test. A portion of the coloured rum taken from the cask before shipment is diluted with twice its volume of distilled water if it is strong rum of the Demorara description, or with an equal volume if of the weaker Jamaica kind. It is then placed in a small cylinder covered over with a glass plate, and allowed to stand for 24 hours. If at the end of this period there is no appearance of cloudiness the rum is free from “faults.” If a cloudiness appears it may be due to :—
(1) Resinous matter from the wood of the cask ;
(2) A precipitate from too-highly burnt colour ;
(8) The presence of low bodies of the fusel oil class which should have been kept back in the low wines.

Other reasons have popped up for faulty rum and I put up a great series of papers the other day.