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Hi there,

Many of you may know me from the bostonapothecary blog which I've written for the last 10 years about explorations in beverage technology. The blog hosts many significant writings on distillation such as the recovered papers of Rafael Arroyo [2], my many translations of French and German papers on rum production, and a near complete bibliography of journal articles published on gin production. For whiskey, I published a data table from a 1968 document that has the detailed production parameters of 42 American whiskey distillers producing 112 different whiskey mashes (85 Bourbons, 10 rye mashes, and 17 corn mashes). I wrote a series of articles called the distillers workbook to, on the lab scale, teach hard to reach concepts in physics and chemistry. The workbook became the foundation of the cocktail centric hotel bar distillation scene flourishing in the UK.

I've advised a lot of people and designed a few products on the market, but there are giant practical holes in my knowledge. I would not even feel comfortable running a distillery until I learned a few more analysis techniques and more about yeast work. I can answer lots of obscure questions by pointing people to the literature, but you have to take a lot of it with a grain of something, because I haven't lived it all yet.


My latest project is the revival of Rafael Arroyo's beloved laboratory still, the birectifier, and it is proving truly magical. I guess I'm a vendor. The blog lately has numerous deconstructions of role model spirits [1,2,3,4,5,6,7,]. Arroyo attributed much of his research success to this device. It is sort of like a scalpel meets stethoscope for spirits. Small samples, such as 250 ml of 40% ABV spirit, are very slowly super fractionated into multiple (typically 8), uniform fractions for the sake of counting congeners and making comparisons. Coupled with a few sub-analysis techniques, it allows the progressive development and reverse engineering of spirits. Arroyo used this for yeast selection, fermentation optimization, still tuning, and even for decisions regarding aging. I've recently been applying it to gin analysis with amazing success.


I've recently recovered Arroyo's own writings about the still and its operation. I've also translated all of the German companion organoleptic tests and have slowly been bringing them back to life. The birectifier solves a lot of problems for a lot of people and I'd be happy to answer any questions about it. They are available and we have a continuously shrinking lead time.

I look forward to participating in the forum. -Stephen

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Haha, I'm simply a nerd that abuses my library card.

I was able to get so many first time digitized inter library loan papers because a connected bar regular wrote a letter to the PBL on my behalf. Typically they slow you down or if something is too challenging, they give up. The PBL has been really amazing. Many of the papers were in library basements or offsite storage. Public librarians must have put many hours into retrieving each individual first time digitized paper.

Studies On Rum came from a Harvard friend who filled out some kind of hardship form to get it out of the reading room. Most copies are reading room only because they are all crumbling to dust. I recently acquired a weird special first edition on better paper with an amazing binding. I have Kervegant's book and that will be scanned next.

The birectifier engineer's drawing was found in a rare German text. In the particular text, it was  Glass companies are finicky or have really long lead times. The first one made was a little bit incorrect so I found a local guy to modify it who turned out to be amazing and liked the project enough to sign on as manufacturer. They can now be made with a realistic lead time.

I have no chemistry background besides youtube and reading Peter Atkins. The significance of the birectifier is that you can get so much out of it organoleptically before you stack titration and other chemical analysis methods on top. It is a tool that at the minimum allows distillers to get so much done by just smell, taste and feel. Tests like the exhaustive test allow you to weight congeners organoleptically without titration. Sometimes adding the titration, with modern high productivity equipment, may cost thousands (often more than the birectifier itself!). All this recent work brings powerful tools affordably, and without being a full fledged chemist.

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"Reactions" is one of the books I'm reading based on your recommendation. Thanks for all the work you do. Even though I am not a rum person I have learned a lot about flavor development reading through the Arroyo's works and other information from your website. 


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The surprising and very cool thing about Arroyo is how all his advice travels far beyond rum. The birectifier deconstructions are turning up rum oil-like terpene fractions left and right (fraction 5). Initially, I was stressing about finding them in rum to validate his work, but then they were turning up gloriously in pear eau-de-vie and even Overholt rye!

My last deconstruction of Fortaleza tequila was the most fascinating relative to Arroyo's advice. He went to great lengths to figure out how to create ferments that could be distilled at low proofs, both to capture more terpene fraction and to create less aroma breakage later on. Well, tequila seems to do it relatively effortlessly relative to rum. My big wild theory, which started in my sensory sketches post, is that sensory properties of the terpene fraction allow a spirit to contain more of other categories like fusel oil and still remain harmonious on a sensory level. Some substrates unlock their terpene fraction easier than others as may be the case with agave or rye relative to molasses.


(Pictured in the center left flask is the terpene emulsion from fraction 5 of Fortaleza tequila.] 

To create whiskies that maximize their potential, we may, just like Arroyo, have to become terpene fraction obsessed. For the rum distiller, this may be achieved by yeast selection while for the rye distiller, it may be in the grain selection. No one really knows, but now with the birectifier, we have the tool to look. I aim to take some different grains scaled for potential alcohol and distill them unfermented with the same amount of absolute alcohol added to see if a terpene fraction appears without the need for fermentation. A similar idea appeared in the Distillers Workbook exercise #9, but now it needs re-explored with the birectifier.

I'm just about done reading Adam Leith Gollner's The Fruit Hunters where he described the world and culture surrounding rare fruit, most of which do not make it to the market. What I suspect is that with the new more lax distiller's laws, ideas from Arroyo can be translated to fruit eau-de-vies and a lot more heirloom fruits kept viable with the fine alcohol market. Pursuit of the terpene fraction by producers and consumers will drive a lot of interest. The birectifer for analysis will allow a lot of precision production on the very small scale.

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What a cool setup.

I'm curious, on the dephlegmation vertical riser that appears to be an allihn condenser connected to a claisen and that coiled glass space with thermometer connection: Is that a dead air space, or is it connected to a heat exchange fluid circuit of some kind?

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It has an air cooled dephlegmator and vapor goes through the part that looks like a claisen. The bi in birectifier is because it is a rectifier in a rectifier. The earliest version of it is from at least 1907 where the internal rectifier was just straight. The vapor goes up the outside, is condensed in the air cooled dephlegmator, down into the internal rectifier and then out. Eventually a vapor trap was added to the dephlegmator and a return tube connecting the second rectifier back to the first which prevents pressure from building up and allows everything to come to an equilibria.

It was first used for beverage work by Dr. Karl Micko and eight fraction analysis is/was referred to as Micko distillation. When Dr. Luckow got a hold of it, all the proportions were optimized for a 100 ml of absolute alcohol scaling system. Luckow and Wustenfeld developed all the companion techniques like the exhaustive test which is an alternative to complicated titrations. Things were mostly developed when the still reached Arroyo, but he was the first to systematically apply the tool to yeast selection, fermentation optimization, and maturation.

Everything was shaken up by WWII, the post war economy, and then the untimely death of Arroyo in 1949. The last reported use of the tool was in Trinidad in 1953 as part of a PhD thesis. My first edition copy of Studies on Rum own by a Seagram employee had a single page "photostat" in it of a 1945 International Sugar Journal article on the birectifier that wasn't in anyone's bibliography. Who know if Seagram guys ever used one. Arroyo did correspond with Paul Kolachov who is acknowledged at the end of Studies on Rum.

We almost didn't think the thing would work just by looking at the drawing, but it generates a wild amount of reflux. By a quarter way through the 5th fraction, you've exhausted all 100 ml of absolute alcohol. No off the shelf glass parts can do that. The only micro distilling units that can are "spinning band" still and they cost pretty startling money. A friend is a micro distilling expert and he optimized all the fittings so the thermometer ports are threaded and the condensor joint is a ball style to reduce stress and opportunity for breakage.

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