Understanding Pot Stilling and Aging: a must read!

[Capn Jimbo]

Let's start here...


http://homedistiller.org/equip/designs/make_pot

This link is a competent and understandable article on the process of pot stilling: from yeast and fermentation, through the double distillation by a classic pot still, separations and aging. It is not a long read but a very, very good one. You will come away with a MUCH better understanding of how the art works to produce a variety of profiles from light to heavy.

It really is a must read if you wish to better understand spirits. For now I'll share its opinion on the relative importance of the various stages of spirits making insofar as contributing to the quality of the final product...

For a whisky

5% barley variety
5% yeast strain
10% wash still (first run)
10% spirits still (with 5% being still shape and size, and 5% for the cuts)
10% barrel's previous use
60% aging protocol

Of course these are arguable, but not by any of us? Or maybe not...

[Hassouni]

that writeup and this image

would suggest that the wooden vat stills are indeed producing pretty heavy distillate, so maybe the rectification isn't as calamitous as it's made out to be?

I'd be very interested to know if the PM and Versailles distillates aged and bottled independently have gone through the column.



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Capn's Log: to the best of my knowledge, all the output of the V and PM pass through both a retort and a column recfifier. I recall that there really is a pure pot still there, which I believe is in the background, called a "high ester" still.

[Capn Jimbo]

If, if, if.....


Let's begin with the fact that this article is discussing classic pot stilling using a typical standalone copper pot stills (think whisky), which the DDL system is not. There are far too many variables to make that assumption beginning with the fact that what looks like spirits pot stills are really not run as one:

http://rumproject.com/rumforum//viewtopic.php?t=1210
http://rumproject.com/rumforum//viewtopic.php?t=1211

In both the case of Versaille and the Port Mourant the first structure is being used more like a boiler or wash still, still true for the second structure of the PM (which is now acting like a retort or secondary wash still). In both cases the vapor is subsequently bubbled through a retort (for further distillation) than, rises through a column (rectifier) which is doing the final distillation, before finally reaching a condenser.

All of this is very un-potlike. Whether a spirit is heavier or lighter has much to do with the initial heat - if rapid the vapor wiil be heavier, if slower there is more reflux (lighter). The initial structure is flat-topped which tends to increase reflux(lighter). The second faux-pot is simply acting as retort wherein the vapor from the first bubbles through wash in the second, which tends to lighten the spirit. The following retort does the same, and the final column absolutely is designed for varying amounts of reflux to again lighten the spirit.

Hass, I know where you're coming from (the notion that a downturned lyne arm promotes a heavier spirit - but - only if that downturn continues directly downward into a worm condenser. And only if the still is running hard, and, and... There are multiple other factors than can favor lighter or heavier distillate. Further, there is no indication of if or how cuts are made with this complicated system.

If Pussers is an example of the PM, we can only assume the output is heavier, but that is all and only for Pussers. Depending on how the whole system is run, amount of heat, and the speed of the run, the design of the rectifier. - the output can be quite variable. If I recall I remember an interview with one of the distillers who verified this.

In sum, it is simply impossible to isolate one design factor as a predictor of the output.


Answer #2:

"(Woudn't this image)... suggest that the wooden vat stills are indeed producing pretty heavy distillate, so maybe the rectification isn't as calamitous as it's made out to be?"

Now we're getting into Distillation 102. You are confusing a wash still (first run, for stripping) with the spirits still (the final run, what most think of as the classic pot still). "Wash stills" are often large, bulky and ungainly vessels that you would probably not recognize as a pot still. Their function is to simply heat the ferment (wash) in a fast, hot process to remove all the alcohol, plus all the nasties, thus concentrating the alcohol from say 7 or 9% (the ferment) to perhaps 25% (low wines). This is a crude, non-discriminatory process).

When you see a beautiful copper pot still (think Scotland) you are usually looking at a "spirits still" (although some wash stills are copper too). The 25% "low wines" - free of the leftover ferment is what is loaded into the spirits still for a much slower, much more careful "spirits run" which creates the final distillate (usually 65-70%). This is where still design comes into play: it's shape, the neck, the lyne arm, various cooling schemes, reflux considerations and the like, leading the vapor to various types of condensers. The number of factors here is tremendous, and controlling them is a high art that defies science. The output of the condenser is low and slow and is constantly examined by the master distiller who makes the final separation and decides just what he wants. Based on these many interacting factors it is possible to produce varying distillates, heavier or lighter, and including various alcohols and even a bit of heads or tails, as the master distiller desires.

What you seeing in the Versaille and PM picture are what look like spirits stills, but which are being used as crude boiler or wash stills producing low wines. There is a huge difference. What a single, final run by a classic spirits pot still can do, is being done here by a combination of retorts and a rectifier.

Capish? God help us all here. If you haven't noted already da'rum is carefully allowing me to spin slowly, slowly. slowly in the wind... as well he should, lol.

Another resource for the anal retentive:
http://whiskyscience.blogspot.com/2011/ ... ation.html

[Hassouni]

Excuse my ignorance but isn't the retort part of any pot still? I've heard it used as a synonym for the lyne arm, but I'm not a distiller nor have I studied this stuff carefully.

I think we need one of the Europeans with access to some indie PM or VSG rums to chime in!



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Capn's Log: No. A basic pot still is A pot with neck, and a lyne arm leading directly to a condenser, in the classic still a "worm" and bucket:

http://rumproject.com/rumforum//viewtopic.php?t=1208

[Capn Jimbo]

Understandable...


Unfortunately, there are a lot of terms tossed about like retort, doubler, thumper and slobber box. Except for the last, the first three are synonyms for a small, closed and unheated container filled perhaps halfway with low or even high wines. The vapor from the pot still was delivered so as to pass through the liquid in the the retort/thumper/doubler as a sort of second distillation. These add-ons were used by later distillers to allow the wash to be distilled to say 80% in a single run, rather than the two runs required by a standalone pot still (the stripping run and the spirits run).

Here's a hobby setup with two retorts/thumpers/doublers:



The "pot still" is on the left. It is loaded with a wash (about 7 to 9%) and is heated, with the vapor passed through the liquidi in two unheated small retorts (aka thumpers, aka doublers). The retorts are typically about half full of liquid which absorb the alcohol vapor until a certain temperature is reached, and a redistillation occurs in each retort. From the second retort the final vapor is delivered to a condenser, where the vapor condenses. At this point the distiller makes the cuts and separates the hearts from the heads and tails.

This setup (two retorts) will result in about an 80% distillate. Note that this hobby setup allow you to remove the two retorts and run it as a classic pot still, wherein the vapor passes from the still directly to the condenser. Here's a real world setup in Jamaica...




This is quite the same with two retorts/thumpers/doublers but runs from right to left, with the heated pot still on the right and a worm/condenser on the left.

Keep in mind that a classic, standalone pot still delivers vapor directly to the worm/condenser and requires two runs: a fast stripping run to reach 25% and a final spirits run to perhaps 70% or less. The issue with the DDL setup the combination of an added retort AND a rectifier column (where the vapor rises from bottom to top) before final delivery to a condenser.



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BTW, if you were wondering about the "slobber box" - this looks like a retort, but the vapor does NOT pass through the liquid in it. Instead the slobber box is there only to capture any ferment spit out of the still to prevent the lines from clogging and causing an unwanted (and dangerous) pressure buildup.

Don't agonize over the terminology. Retort has several uses, but the above description is the most common use of the word by distillers (a separate, secondary device).

[Hassouni]

How does the vapor get out of the retort if it's unheated and the vapor meets liquid (water, I presume?) inside it?

[Capn Jimbo]

How does the vapor get out of the retort if it's unheated and the vapor meets liquid (water, I presume?) inside it?

Read the above post again. The retorts can be filled with water, but they are almost always filled about halfway or less (too much liquid creates excessive back pressure), with either low or high wines. Early in the run they absorb all the alcohol/vapors until the heat of the vapors finally bring the liquid back up to distillation temperatures and the re-distillation takes place. This of course is repeated in the 2nd retort.

This set-up has been called a "rum still" since it was and remains common as a modifiication of a classic pot still for the purposes stated.