The Black Tot wrote:.
NOW, I'm going to come forth with some stupid questions.
Keep in mind you are questioning Moi - the Compleat Idiot of Rum. But I'll do my best, great post, thanks...
Wort in malt is the sugar-rich liquid which is drained out of the mash tun (basically heated vat) where the grains are soaked and heated until the sugars infuse into the water. In bourbon, the grains stay in what becomes the "distiller's beer" or mash for the fermentation process. In malt, they don't.
Since in rum we're dealing with cane juice or molasses, what's the deal with rum wort? Since the juice/molasses are already a liquid, is the wort in this case just those things diluted with water to a certain degree? What degree? In short, wort the f are we talking about here? (couldn't resist)
As I understand it, fermented cane juice is filtered before stilling to remove miscellaneous detritus. As for molasses based rums, one of the BIG issues are the many solids inherent in the wort/wash, which can end up burning and collecting in the bottom of the pot still, particularly those that use direct flame or heat.
Some single malt pot stills have a device that amounts to a series of chains that are caused to rotate around the base of the still, to prevent this accumulation and burning. For rum, this simply means giving the still a good cleaning after every batch or two (which is why pot stilling is expensive).
To break it down to the basics for new readers (and to check my own fuzzy understanding here), when you heat up wash/distiller's beer, alcohol boils first, at a lower temp than water, so distilling is the art of capturing the flashed off alcohol leaving the water and (in bourbon's case) mash residue behind.
So the wash is boiled in the pot and then rises up through the "retort" (f'ing hell. Let me find an easy definition of a retort - OK, so the retort is the inverted funnel at the top of the pot including the >90 degree elbow in the top. In other places this is called an alembic (cripes - you see why this is tough to get straight? Er, keep bent?)).
The first boil-off of the wash/distiller's beer goes up through the retort/alembic and ends up bubbling through a relatively cooler (but still hot) tank of "low wines" - basically the first distillation stage with alcohol up around the level of (in reality slightly stronger than) most wine. This is because the boiloff process isn't as picky as we'd like and a lot of water still gets up the retort with the alcohol.
Another example of the rubbery words used. In the pics above the "retorts" are the two smaller pots/containers that are situated in series, and as used the term does NOT refer to the alembic/pot still. Thus the vapor from the pot still passes in turn through both of the secondary retorts before reaching the condenser. This is really a matter of common usage rather than dictionary definitions. Technically anything that distills a liquid could be called a "retort" (particularly the glass versions used in chemical laboratories) - but in practical use - a pot still is called, well, a pot still. An "alembic" was the historical term used for the beautiful, hand tooled and graceful copper stills, still made in Portugal, et al. The difference between a "pot still" and "alembic"? None really. The most used term? "Pot still". Although technically an alembic/pot still could be called a retort, this usage is rare. In practical use in stilling of rum or whisky, the term "retort", which may be referred to as "copper refining recipients", refer to secondary, in-line components which are just the "pot" part of a "pot still".
Trust me, if you start calling a pot-still/alembic (or any of its four parts) a "retort", you're going to get a lot of blank stares from most distillers. Clear as mud, eh?
At a recent tour of the Kilkerran distillery (Glengyle), something was mentioned that caught my interest. The stills there were bought from a shuttered distillery called Ben Whevis (not to be confused with Ben Nevis - I asked). The retorts on these stills are VERY tall, and the guide said that this gives a lot of opportunity for the boiled wash to condense and start to sink back down through the upward flow of the boiling alcohol vapor.
The term "retort" means "return", but is being misapplied. A pot still/alembic has four basic parts: the "pot" (literally), the "neck" (aka "swan neck") which is a smaller chamber situated just above the "pot", the "lyne arm" which is the small tube or passageway leading the vapors more or less horizonatally, to the "condenser" (a large container or chamber filled with cool water, through which the vapors pass through within a coil or series of usually copper tubes).
The part you are calling a "retort", is actually the "neck" - these come in all shapes and sized, some squat and short, some taller and narrower. The taller the neck, the more likely that some of the vapor will condense near the top of the neck and drip back down toward the pot (this return/retort of liquid is called "reflux"). The refluxed liquid is then redistilled and the vapor is more refines.
This results in a sort of turbulence which he described as "reflux" - this caught my attention because the word reflux is used sometimes to describe why the El Dorado wooden pot stills are so special (apparently those have some very unique and important reflux characteristics which, when operated with a skilled hand, result in some very special stuff). Apparently reflux results in a lighter, more floral whisky. I was trying to come up with how this turbulence would physically affect the distillation, but I came up short. In other words, I (think I) know tall retorts encourage reflux, which leads to a lighter and more floral result, but I'll be damned if I know how or why - is it because the "heavier flavoring" molecules which are also represented later as the tails have a harder time escaping a higher chimney due to their comparative mass, and mostly fall back down into the pot?
That's a fair description. Think about the lyne arm as well. If it slant upward for a way, the output will be lighter; if it slants down, a heavier output can be expected. I will only disagree in that I would not necessarily generalize that a taller neck will result in a more floral output, as pot stilling in general leads to a notably heavier spirit in general.
At this stage, I'm unclear at how it makes it to the next tank. Is it again heated in the low wines tank? Ah yes - in the Hampden picture I can see what looks like steam jackets around the low and high wines tanks, with what appear to be stainless pipes for delivering steam coming in through the top. In the top pic, the heating mechanism is not so easily observed. Are the pipes coming off the bottom of these wines tanks for the delivery of a heating medium/fuel or are they for shunting some of the wines back to the pot?
This is an EXCELLENT question. Let's start by considering the simplest pot still/alembic which leads directly to a condenser - no intermediate retorts at all. The first run is a sort of stripping run (often done in a larger pot, which some call the stripping still), which results in an output of about 35% alcohol ("low wines"). This is often a fast run, as the idea is simply to capture alcohol in general. This first run then becomes the wash for a second run, sometimes in a smaller still, and sometimes called the spirit run or spirit still. This is the money shot, as the distiller - by eye, nose and palate, attempts to capture mostly the "hearts", or center of the rum. The early and nasty heads and late tails are captured separately and are called the "high wines". The captured hearts are around 65%, are saved and aged in good wood (at so-called barrel strength).
Now? Now we can speak of the two intermediate "retorts" (simple pots, no neck). These are used with one goal: to eliminate the need for two stills/two runs, but to accomplish a similar result in a single run. As before the pot still/alembic delivers a vapor at about 35%. The first retort is about 2/3rd's full of water and/or low wines. The vapor from the lyne arm of the original still is guided by a copper tube to the BOTTOM of the first retort, where it then bubbles up. At first it condenses, but at a point the low wines in the first retort are heated by the vapor, and a higher alcohol (higher than 35%) escapes the first retort as output, which is similarly guided to the bottom of the second retort (which contains high wines). The output of the second retort is accordingly much higher, closer to 65% or so, and THEN is guided to the condenser, and final capture of the hearts.
By using two retorts, the concept is to achieve a 65% in a single run.
So we basically heat again, and more alcohol jumps out, leaving more water behind at each stage, thereby concentrating the abv of the liquid. For some reason, out of the low wines tank, we don't have a retort/alembic, so much as we have a basic pipe. Question: Why not a second alembic with a similar shape?
Actually El Dorado's Morant double pot does exactly this, but the product will be less refined. The pot with two intermediate retorts is like a triple distillation, while ED's double pot distills only twice.
I think it's confusing to call the 2nd and 3rd stages "retorts" if the retort is by definition the bendy pipe connecting the tanks (am I wrong about this?). Low wines tank, high wines tank, and mention of the additional heating stages in these might help the beginners. Just in preparing this post I'm learning things by forming these questions, which is part of why I'm doing it.
Right. It is confusing, and descriptors unfortunately get tossed around. All I can tell you is that the most common usages are the "neck" or "swan neck" for the pot still/alembic, and "retort" for the intermediate containers.
Once we've gone through these three boil-offs (original pot, low wines, and high wines heated tanks), the first parts of the now high-proof alcohol that boil off are known as "heads" - these are undesirable, and contain lots of the crap that was infamous for making amateur moonshiners blind. These are somehow shunted out of the system (not sure precisely through which conduits in the apparatus above?).
Actually it was not the heads as much as it was the use of automobile radiators and leaded solders of cheap sheet metal that caused blindness. It is only at the end - the drip, drip liquid capture - where the heads and tails are separated out and disposed of (or recycled to the retorts or even to the original pot still/alembic). This is a good time to note that most pot stilled product still contains some heads and tails, as there is not a clear division between them. For example as the heads are diminishing, the hearts appear and are increasing: there is crossover. Not to mention that many distillers WANT some of the heads/tails in the final capture.
Heads and heart are determined by measuring the specific gravity of the condensed high proof spirit, often observed by a floating graduated device (such as we use for our sugar tests here on the project). These SG meters are viewed through a small enclosed windowed box also known as a "spirit safe".
Once the SG increases to the point at which the start of the "heart" (the good stuff) is found, the produced liquid will now be shunted into the "keepers" tank, basically.
Exactly, but know that the same crossovers are noted, and some heads/tails will make it into the final capture, unless the distiller is willing to throw away much good output to get just the "heart of hearts" (like Barbancourt).
Right. After the heart spirit has passed through and been captured, you have another undesirable component of the alcohol known as the "tails". Heads and tails together are grouped into "feints", which can be said to be the combined undesirables of heads and tails.
An important part of the role of distiller is choosing when to start and stop capturing the heart of the distillation. As I understand it, cutting in too early (too low a SG, too many heads included) will result in a very estery, wild beast, headache-inducer of a product - HOWEVER, the chemistry involved in aging spirit in oak barrels does a good job of taming this, which is why cuts with more heads respond well to longer aging in oak, where those heads are developed into longer chain molecules which result in some very complex and delightful flavors. Since we're talking about Jamaicans today, I'm supposing these guys are used to including about as much heads as they can possibly get away with, because as a category Jamaican rum is famous for its relatively high ester content.
Yes.
Adding dunder to wash is analogous to what in bourbon they call the "sour mash method" - a highlypopular process in which a certain volume of leftover distiller's beer sludge aka "backset" is added to the fermentation tank to goose the fermentation or otherwise propogate the development of other flavors during the fermentation process.
Yes, again.
Dunder is just more inherently disgusting in nature, seemingly born of a quest to figure out just exactly how gross you cold make a liquid, and then taking that to the next level
Whatever. Some of the world's most wonderful vegetables we must remember are grown in manure. Eat and drink up.
From garbage comes ambrosia, lol.
1. As the distillation process goes on, the leftovers in each of the pot, low wine and high wine tanks must increasingly be made of water/larger molecules. When we say that alcohol "comes off the still" at a particular proof, doesn't that proof gradually decrease over time as the wines heat up and more water tags along to the next stage?
That's why the intermediate retorts also have drains, which can be guided to another retort, to the original still, or to waste.
2. You mention that a portion of the low and high wines get passed back to the pot still for redistillation - what is the reason for this?
To concentrate the flavors.
3. Why is this called "double distillation", when the liquid seems to be heated and captured 3 times?
It isn't. You could call a triple, or you could consider it a single distillation (since it is a single run).
4. Copper is utilized as much as possible in order to remove some ugly compounds, which happen to adhere well to copper. Particularly sulfur. What I don't understand is how copper continues to work on the inside of pipes without being scrubbed clean after each pass, which by the looks of these stills isn't practical. What I mean is, sulfur reacts with copper, I get that - but then it forms an oxide layer. Surely after a still has been run for a while, that copper oxide builds up until the vapor is mostly in contact with oxide rather than fresh copper, which to my mind wouldn't react very much. How often are the internals of these pipes scrubbed/buffed such that fresh copper is exposed for sulfur absorption? I can see access holes in the tanks, are these buffed from the inside to bare copper between each run? It doesn't look practical or even possible to buff the insides of the retorts
.
It would be rare to scrub it I would think, and there is no need to be so scrupulous for the entire system, as it apparently doesn't take a large area of exposed copper to do the job. Another notion is that the copper acts a catalyst, and doesn't directly react with the sulfur, but converts it. The home distiller boyz clean with water, the end slops, etc., in a "cleaning run" from time to time. This is a very interesting question, and I'll contact Richard about this.
http://www.a-holstein.de/index.php?id=182
http://homedistiller.org/forum/viewtopic.php?f=1&t=9299
5. What other compounds other than sulfur does copper ameliorate?
There are a bunch, but one frequently mentioned is ethyl carbamate (from fruit brandies, etc.).