ABV dependent volatility of fusel oils

[Bagasso]

I know this is an old thread but I don't think I had ever seen it before and the first graph got me thinking about the advice to water down your low wines to around 40%ABV when doing a spirit run.

If the graph is correct then doing this makes the separation of methanol, propanol, isobutanol and isoamyl in a pot still more difficult.

Using the V2 calc for pot still purity on the parent site with the following values:
40% ABV
20L
1200 W

you would run for an hour before the ABV in the pot dropped to 30%ABV and end up with approx. 4 liters of 76% distillate from this hard to separate mix.

[Kareltje]

Some research is done in Brazil on the discontinuous distilation of cachaca from sugarcane. For example:
http://www.scielo.br/scielo.php?script= ... 0000300005" onclick="window.open(this.href);return false;" rel="nofollow

Or the various articles to be found with:
"Volatilization kinetics of secondary compounds from sugarcane spirits during"
For example:
http://biblioteca.versila.com/?q=sugarcane+spirits" onclick="window.open(this.href);return false;" rel="nofollow
Unfortunately the latter link gives the studied aspects, but not the conclusions.

The concentration of the cogeners is sometimes given per 100 ml absolute alcohol (aa ) but can be plotted again per 100 ml distillate. I myself was interested in methanol, but fusel oils are studied too.

[Odin]

Interesting reads, Kareltje! Thanks for sharing.

Odin.

[der wo]

Edwin linked this thread yesterday. Here: viewtopic.php?f=1&t=70666

I have read this old thread again today and want to answer Bagasso, although he asked in 2016:

I know this is an old thread but I don't think I had ever seen it before and the first graph got me thinking about the advice to water down your low wines to around 40%ABV when doing a spirit run.

If the graph is correct then doing this makes the separation of methanol, propanol, isobutanol and isoamyl in a pot still more difficult.

Only if you do the spirit run with a potstill, in theory after watering down it would be more difficult to cut out the isoamyl alcohol with the tails. As long you use a reflux still, watering down will only cause the isoamyl concentrated layer being a few cm higher or lower in the downer part of the column. (Edit: watering down has also other effects. But this is off-topic.)

[Bagasso]

Only if you do the spirit run with a potstill, in theory after watering down it would be more difficult to cut out the isoamyl alcohol with the tails. As long you use a reflux still, watering down will only cause the isoamyl concentrated layer being a few cm higher or lower in the downer part of the column. (Edit: watering down has also other effects. But this is off-topic.)

I did single out the pot still because of the smearing factor.

I do not understand why you think isoamyl in the tails is the only problem. The chart is not plotted against a timeline. It is applied to the content of the pot depending on the ABV of the liquid inside it.

Therefore if the boiler has 40% ABV: isoamyl, isobutanol, propanal and even methanol are so close to the same volatility of ethanol that they would be smeared.

[der wo]

I do not understand why you think isoamyl in the tails is the only problem.

I don't think, it's the only problem. It's one of the problems. Perhaps I placed the "only" wrong. Sorry. "watering down will cause the isoamyl concentrated layer only being a few cm higher or lower in the downer part of the column." is better?

The chart is not plotted against a timeline. It is applied to the content of the pot depending on the ABV of the liquid inside it.

Which one of the charts? All those charts don't need a timeline:
- The first chart is the volatility of different congeners in dependence of the ethanol concentration. How the congeners behave if the boiling liquid is higher or lower in abv. Liquid means not only the wash or low wines in the boiler, but also the liquid in the column.
- The second chart has something similar to a timeline: the amount of collected distillate -line. And shows how the isoamyl concentrates in the heads of a single run and during the first half of a double run (means spirit run probably).
- the third chart is a sketch of a column and shows where the different compounds accumulate. For example the isoamyl around plate no.6 of total 40 plates.

Therefore if the boiler has 40% ABV: isoamyl, isobutanol, propanal and even methanol are so close to the same volatility of ethanol that they would be smeared.

In the boiler yes. But not in the column at higher abv. "Volatility" means vapor from a liquid. No matter if in a boiler or in a column.

[Bagasso]

Sorry. "watering down will cause the isoamyl concentrated layer only being a few cm higher or lower in the downer part of the column." is better?
Which one of the charts? All those charts don't need a timeline:
In the boiler yes. But not in the column at higher abv. "Volatility" means vapor from a liquid. No matter if in a boiler or in a column.

My post was about the first chart and in reference to pot stills.

I know the OP was focused on columns but I was just thinking about what that chart meant to pot stills and the recommendation to water down to around 40% ABV for a spirit run.

[der wo]

Ok, now I understand.
If the chart is true, a potstill stripping run without cuts collects not only all ethanol but also all isoamyl. Then the spirit run with 40% in the boiler will start with a similar ratio of isoamyl and ethanol like in the low wines. And then during the hearts a higher ratio between isoamyl and ethanol is distilled over. So when the tails start, much or most of the isoamyl is already in the hearts. If there is any isoamyl left, it will be in the tails. So after the spirit run is in the hearts a higher concentration of isoamyl than in the low wines was. The second run had bad effects on the isoamyl concentration.
Similar but less extreme with isobutanol and propanol.

What does this mean?
Is this the reason, why you never get such a good neutral with a potstill like with a column? Is the isoamyl/isobutanol and propanol amount only a small part of the fusel smell and the other fusels behave different? Are other benefits of watering down more worth than the problem with the isoamyl?

[Bagasso]

What does this mean?
Is this the reason, why you never get such a good neutral with a potstill like with a column? Is the isoamyl/isobutanol and propanol amount only a small part of the fusel smell and the other fusels behave different? Are other benefits of watering down more worth than the problem with the isoamyl?

I think it means that at lower ABV these 3 fusels come off mostly in the heads.

Thinking about this I pulled up photonic's lab results and sure enough his lab results show:
[columns]
Fusel------------>Fores/Heads----------->Hearts
Iso-Amyl ------->1769 mg/l -------------> 840 mg/l
Iso-Butanol ---> 419.1 mg/l ----------->166.1 mg/l
Propanol -----> 171.7 mg/l -----------> 97.8 mg/l

This was from a 15% wash, which seems to show this same thing as well as showing that things smear a lot in a pot still. When I made that post in 2016 I was wondering how much of the heat was actually from these solvents.

I wish he had posted the "hearts" without filtering.

[der wo]

The numbers match to Edwins graphs I think. The volatility of isoamyl is lower at higher abv (fores/head) than at lower abv (hearts) indeed, but this doesn't matter in a potstill stripping run, because the volatility of isoamyl is higher than the of ethanol all the time, and after the heads there is much less isoamyl left in the boiler.
But 40%abv behaves different than 15% probably. According to Edwins posts at least. His 2nd pic for example.

He wrote that this behaviour at low abv is an argument for making stripping run fores cuts. Sounds logical, but looking at the smearing I think it will help only little.

Also one of Kareltjes links shows graphs with isoamyl much more in the heads than later.

Do you think this heat is also there with refluxed spirits?

[Bagasso]

The numbers match to Edwins graphs I think. The volatility of isoamyl is lower at higher abv (fores/head) than at lower abv (hearts) indeed, but this doesn't matter in a potstill stripping run, because the volatility of isoamyl is higher than the of ethanol all the time, and after the heads there is much less isoamyl left in the boiler.
But 40%abv behaves different than 15% probably. According to Edwins posts at least. His 2nd pic for example.

That was what I got from the original post. I wish that graph was clearer. When you open it in a different tab the x and y axis are black, so who knows what the measurements are.

Had a hunch it might was the navigator and opened it in firefox. Now I can see the whole image and now I'm wondering why they are measuring different things, "ml/100ml pure etho" and "mg/l distillate" and what it actually means. Will have to think about that when I have some time.

He wrote that this behaviour at low abv is an argument for making stripping run fores cuts. Sounds logical, but looking at the smearing I think it will help only little.

Well if people make cuts and end up with something they think is smooth then I think it is just a matter of efficiency. Kiwistillers guide to cuts talks about 2-3 liters of heads. At some point the amyl and/or whatever makes heads hot/solventy runs low enough to go unnoticed.

Do you think this heat is also there with refluxed spirits?

I don't have a reflux still, I started with a boka but it sprung a leak before I had gained any real experience and stuck with pot stills since then.

[der wo]

Well if people make cuts and end up with something they think is smooth then I think it is just a matter of efficiency. Kiwistillers guide to cuts talks about 2-3 liters of heads. At some point the amyl and/or whatever makes heads hot/solventy runs low enough to go unnoticed.

Yes. Sounds plausible.

[Birrofilo]

Foreword: I am assembling my first still, but I think theory come first, practice second. I want to have a clear picture in my mind of what happens, before making it happening. That's the goal, at least.

I am very confused by this entire thread. I think I might not be the only one, as this goes against the Received Gospel and I am not ready for a Reformation in distilling theory. I need to place this new tile in the mosaic so that it makes a coherent image.

So far it was clear to me that methanol and acetone and such stuff were lighter than ethanol, would tend to come off earlier, and the initial part of the run would be richer in such stuff than the middle part or the end part. Also, it was clear that heavier than ethanol alcohols, which we will call "fusel oils" for short, would tend to come out in higher concentration in the last part of the run, the "tail". Let's call this the "canonical behaviour of fractions".

Now we learn that the "canonical behaviour of fractions" is valid only above a certain alcohol content, let's say above 40%, but in reality more than that. For low-alcohol content, the volatility of the various fractions does not conform any more to the canonical behaviour. We have fusel oils mixed with the heads and the heart. Let's call this the "paradoxical behaviour of fractions".

In order to check what can be made, as practical knowledge, of this thread, I will write some thesis to be derived by it. Please flag each as C (correct) or H (heretical).

1) Considering that wash has a low alcohol content, and that with low alcohol content fusel oils have the same or higher volatility than ethanol, and are therefore not easily separable in the tails, it never makes sense to make cuts during the stripping run. Also, considering that methanol has the same volatility as ethanol in the low-alcohol wash, and that it is not separable in the foreshots, it never makes sense to separate foreshots during the stripping run. That results in this practical rule: collect everything during the stripping run, and postpone all rectification for a later phase. (C or H?)

2) If we have 40% ABV alcoholic vapours, we will never manage to obtain "neutral" spirit because, at that strenght, the volatility of fusel oils is the same as ethanol's. 40 plates in a reflux still or 40 runs with a pot still wouldn't do. We are not into the "canonical behaviour" of fractions and we will not separate anything. (C or H?)

3) If we do the second run (the spirit run) with a pot still, and we start with 40% ABV, the condensing vapours in the still will have a ABV higher than 40%, and will begin to move into "canonical behaviour" region, but just as a trend. We will not have a ABV such as to exhibit a true canonical behaviour. We will not obtain good neutral, and we will transition very slowly into stinking tails. (C or H?)

4) With a reflux column after some time we will have the water content slowly precipitate into the kettle and will have the entire column with a high ABV on its entire lenght. When we begin collection, we will observe the normal sequence: stinking foreheads, heads, good neutral, and increasingly stinking tails. A reflux still charged with 40% ABV low wines always puts us in a situation of "canonical behaviour" and allows a correct rectification, stinking foreheads will come out first, fusel oils will be on the tails. (C or H)?

5) During a long run, fusel oils collect in the lower part of the column. If they are not bled, they will form a sort of stopper which will cause the collection to be dirtied with fusel oils. This happens only because the column has a finite volume. If the kettle has a small volume and the column a relatively large volume, the stopper effect never happens because the entire middle run can be completed cleanly. Bleeding becomes necessary because the run is long and there is no way to get rid of the fusel oils accumulating in the lower part of the column. (C or H?)

5bis) This long run is a subset of the proper column distiller, as seen in refineries, with continuous feeding and continuous bleeding. The home distiller must be wary of not having too large a kettle for a narrow reflux column, lest he creates a "stopper" of fusel oils. (C or H?)

6) Short of a bleeding tap, the home distiller would just stop collecting product when fusel oils begin to appear, and recycle the dunder because the "stopper effect" prevented some good ethanol from being collected. (C or H?)

7) The home distiller who makes a fast stripping run with a pot still, and a slow spirit run with a reflux column, and recycles his tails as is normally done, can in general ignore the information contained in this thread and "do business as usual". (C or H?)

8 ) Those who only do one run, and those who do two runs with a pot still, probably need to read this thread carefully, and probably had results which did not match the Gospel in any case. (C or H?)

9) The stinking forehead that people collect during the stripping run, and eliminate thinking they eliminate Methanol, is instead mainly acetaldehyde. Methanol remains in the low wine and is not collected in the foreshots of the first run. Thinking that it has been eliminated it's a mistake, it will be drunk with the final product.

[Edwin Croissant]

You are on the right track

I will answer the questions I got a direct answer for. The rest will have to wait.

4) With a reflux column after some time we will have the water content slowly precipitate into the kettle and will have the entire column with a high ABV on its entire lenght. When we begin collection, we will observe the normal sequence: stinking foreheads, heads, good neutral, and increasingly stinking tails. A reflux still charged with 40% ABV low wines always puts us in a situation of "canonical behaviour" and allows a correct rectification, stinking foreheads will come out first, fusel oils will be on the tails. (C or H)?

I think that this is correct. As long as you keep the output above 92% ABV or so the tails will not be overly present in the output. Please note that a charge of low wines contains more ethanol and more fusel oils than a wash. This result in a faster saturation with fusel of the column.

5) During a long run, fusel oils collect in the lower part of the column. If they are not bled, they will form a sort of stopper which will cause the collection to be dirtied with fusel oils. This happens only because the column has a finite volume. If the kettle has a small volume and the column a relatively large volume, the stopper effect never happens because the entire middle run can be completed cleanly. Bleeding becomes necessary because the run is long and there is no way to get rid of the fusel oils accumulating in the lower part of the column. (C or H?)

This is correct although there are several ways to keep the fusel concentration low: constant flush by high reflux, periodical flush by going into full reflux after still cannot maintain desired ABV, enlarge bottom part of column (bubbleball) or by bleeding off. Bleeding has been proved to be very effective en efficient, in one run it is possible to produce very clean ethanol. Se this thread on this forum.

[der wo]

1) It makes sense to cut fores at the stripping runs. You not only cut the low boiling point foreshots acetaldehyde and ethylacetate, but also -surprisingly- other substances. But of course it depends what you want to make. Vodka? Rum? All in all your post lacks of the information, what you want to make.

2) The graph is not about the vapor% but about the liquid%!
40 plates of a reflux or plates still would of course do. Because the liquids up in the column are over 90%abv.
40 potstill runs would do also, for the same reason. But of course you must not dilute between.

3) In Edwins second pic you can see a double distillation result: Isoamyl in the heads and hearts. Only if we have way more than 40% liquid, we get into the canonical behaviour. But only at the beginning. We will have no isoamyl in the heads, but in the hearts. The abv in the boiler will drop continuously. And sometime -probably during the hearts- the abv in the boiler will be too low. Only with a reflux or plates still we can hold the abv high during the whole run.

4) A reflux still doesn't need to be charged over 40% to cut the isoamyl. You can charge it with 5%. Then the isoamyl layer will be a few cm higher in the column, that's all.

5) Here on hd only Edwin knows how effective the bleeding off is. I am not able to say how much of the smell is carried up for example by entrainment, if you don't have a bleed off. Necessary is such a construction definetely not.

5bis) Yes, perhaps here is an advantage of a wide column diameter. The fusel layer will remain relative thin. But if you use a much wider diameter than usual, you have to rethink many other parameters too, or the column becomes inefficient. The wattage and the packing density for example.

6) Yes, probably a reflux still with a bleed off can collect more of the alcohol as hearts. But how much? In general a good reflux still can collect almost all alcohol at 95%. But yes, also 95% can stink. At least after diluting to drinking strength. Only Edwin has a solid opinion here.

7) He has to collect the tails also at high abv. Then he either can do as usual or he starts thinking if he could improve the quality further with a bleed off.

8 ) Single run with a reflux still works. I answered this in No.2.
Neutral alcohol with a potstill doesn't work well. You can make with for example the Rads all bran recipe a nice spirit with potstill double distillation, but it's by far not as neutral as with a reflux still.

9) Not only acetaldehyde, but also ethyl acetate. You can smell the fruity or apple like sharp flavor of acetaldehyde at the end of your condenser (potstill) before the foreshots start. And ethyl acetate smells gluey.
Methanol can be cut very well with a high abv reflux distillation probably. Look at the end of the graph, between 75 and 100% the value for methanol is 2. 2 sounds not much. But it counts for every distillation (also theoretical distillation)! And if you have the 2 ten times successively, it sounds pretty effective: Say you have 1000 times more ethanol than methanol. Then after the first distillation you have 2000 times more ethanol than methanol. After the second 4000 ... after the tenth 1024000 times more. You have reduced the methanol content to 1000 / 1024000 = around 0.1% compared to where you started.
Edit: Argh, bullshit!...
I'll try again. After one distillation the first distillate will have twice the amount methanol, after two distillations four times the amount ... after 10 distillations 1024 times the amount. So the methanol is good concentrated in the foreshots.

[Bagasso]

3) If we do the second run (the spirit run) with a pot still, and we start with 40% ABV, the condensing vapours in the still will have a ABV higher than 40%, and will begin to move into "canonical behaviour" region, but just as a trend. We will not have a ABV such as to exhibit a true canonical behaviour. We will not obtain good neutral, and we will transition very slowly into stinking tails. (C or H?)

I think this shows why some of the other things you posted are missing the mark. The first graph in the original post is the volatility of different compounds based on the ABV of the liquid in the boiler not the vapours. So if you start with 40% ABV as the ABV of the liquid in the boiler drops, during the run, it moves further away from what you are calling "canonical behaviour".

[hefezelle]

This whole discussion, and specifically the first image, make me think that when stilling for neutral spirits, one might try to bubble some air through the wash for a while right before charging the still. That would allow for the isoamyl and isobutyl alcohol to evaporate off (and a bit of sacrificial ethanol) before going into the still, so they don't get a chance to build up in the column. Thoughts on this?

[der wo]

Yes. But does enforced evaporation (by heat or air pumping) cut better than distillation? Why not stripping it with a potstill and cutting fores there? Single distillation with a column (without stripping before) for neutral alcohol is a shotcut, which lowers the quality. In any case you need more reflux for a similar purity. And when you now add another step like air pumping, perhaps a double run is purer and faster all in all now.

IMO with a single distillation you are on the wrong track from the very beginning. Also pH rising (ester hydrolysis) of the low wines isn't possible this way. Or perhaps carbon treatment between the runs. And dilution between the runs.

[Bagasso]

Yes. But does enforced evaporation (by heat or air pumping) cut better than distillation?

Forced evaporation by heat is distillation.

Now, is air better or worse? I don't think anyone can say but airing out by just leaving the container open makes a difference that everyone seems to agree on. That would seem to imply that maybe air pumping might do the same, only quicker, with a little more loss of ethanol. Like running a still a little hotter might give a smaller hearts cut, to a point.

[zapata]

Birrofilo, perhaps it is best to sortof ignore most of this sort of talk for now? Of course I don't mean fully ignore, but honestly without a good number of runs under your belt, a lot of this info is useless. The "canonical" practices are not making shit, you will be well served to simply follow proven protocol while trying to understand.
This is not unusual in the physical sciences. Take chemistry for example. In the beginning you learn simple rules and they are usually taught as rules. Then later you learn the exceptions. Later still you learn things are not even that cut and dry with complicated and nuanced equilibriums where the rules are partially followed followed based on some new principle. At the end (or the end of my learning at least) you find the original "rules" were sometimes just decent guidelines to learn principles (but some actually end up being real rules).
I'm not one to question understanding, knowledge or advancement for its own sake. But at the very beginning? By all means follow along, but nothing here undermines canonical practices. Millions of gallons of good booze have been made by people that simply followed the canonical guidelines and recipes.

[der wo]

Yes. But does enforced evaporation (by heat or air pumping) cut better than distillation?

Forced evaporation by heat is distillation.

Now, is air better or worse? I don't think anyone can say but airing out by just leaving the container open makes a difference that everyone seems to agree on. That would seem to imply that maybe air pumping might do the same, only quicker, with a little more loss of ethanol. Like running a still a little hotter might give a smaller hearts cut, to a point.

I would say for distillation by definition the liquid has to boil, and "enforced evaporation" ist something like bringing the temp up to 50°C for a while. And pumping air vs natural airing is like "6 years old Scotch in 6 days!!!" instead of real age. But as long one doesn't rely on shortcuts in every step of the process, perhaps it's all right.

[Bagasso]

I would say for distillation by definition the liquid has to boil, and "enforced evaporation" ist something like bringing the temp up to 50°C for a while. And pumping air vs natural airing is like "6 years old Scotch in 6 days!!!" instead of real age. But as long one doesn't rely on shortcuts in every step of the process, perhaps it's all right.

There is a lot of assuming going on in both of those claims. I personally see no reason why something that is more volatile won't evaporate faster without boiling. That is the basic idea of airing out and the only thing that keeps it from working in spirits at around 40% ABV is that at that concentration everything has very similar volatility.

I think that is the spirit of this thread. Like zapata said, it isn't that traditional practices don't work, obviously they do, but it is not for the reasons that we think they do.

[Birrofilo]

This is a very interestin thread and, slowly, I begin being less puzzled.

I am reassured by zapata's observation that traditional practices do always work. I was wondering in which special cases they would work, and in which they wouldn't (let's say, single run distillation, or low ABV mash, or other cases).
I am interested in the cat to catch the mouse, and if he does it because the mouse is good to eat, or fun to catch, it's not relevant.

This is obviously a very good thread to refine one's understanding of the theory for sure.

1) It makes sense to cut fores at the stripping runs. You not only cut the low boiling point foreshots acetaldehyde and ethylacetate, but also -surprisingly- other substances. But of course it depends what you want to make. Vodka? Rum? All in all your post lacks of the information, what you want to make.

In my mind, in the first run I am only concerned about throwing away water (using a pot still configuration rather than a reflux configuration).

I was puzzled, though, to understand in which cases it made sense to cut foreshots during the first run, or even to make only one run overall. It's time I look for this information on the site without finding it, probably out of choosing the wrong keywords.

Could you elaborate or point me to some other thread where it is explained the different cutting strategies (two runs no cuts in the first, two runs cutting foreshots in the first, one run, three runs) for the different products (rum, whisky, brandy, Geist - or neutral)? A general logic framework.
I understand the playing field for whisky or rum is mainly on tails, and for fruit products in mainly on heads side.

2) The graph is not about the vapor% but about the liquid%!
40 plates of a reflux or plates still would of course do. Because the liquids up in the column are over 90%abv.
40 potstill runs would do also, for the same reason. But of course you must not dilute between.

This mistake of mine was pointed to me also by Bagasso. So it's actually at the end of the distillation that I move away from the canonical behaviour toward the left of the Fig. 1 in the original post.
In fact what I should keep in mind is that, in the upper portion of the column, which is where I collect after all and so what matters to the home distiller, if the column is brought to equilibrium before beginning collecting, I always have the canonical situation until the end of the run.
In the final part of the run one collects fusel oils in any case.
Before this thread I would expect to collect fusel oils at the end of the run because they are less volatile.
Fig. 1 tells me I am collecting them now because I have a low-alcohol mix in the kettle at the end of the run, and in this situation fusel oils come up faster than at the beginning of the run. But the collected spirit wouldn't change because of this new knowledge! The cat catches the mouse in any case.

[hefezelle]

When i wrote

This whole discussion, and specifically the first image, make me think that when stilling for neutral spirits, one might try to bubble some air through the wash for a while right before charging the still.[...]

i perhaps should also have included my trail of thought and more context, but i only realize that now. Apologies.

der wo responded with

Yes. But does enforced evaporation (by heat or air pumping) cut better than distillation? Why not stripping it with a potstill and cutting fores there?[...]

True, stripping in potstill mode and cutting fores late or doing a heads cut is probably a good way to get rid of the isoamyl etc. But i was not aware of that, i thought potstill stripping was done because it's less of a hassle than refluxing, and i thought that no cuts needed be made, since a stripping run with reflux column would follow. So i stripped in reflux mode, collecting heads to tails at high ABV, which will make it difficult to manage the higher alcohols when they build up and essentially shorten my column on the spirit run.
Bummer, those components would have been easy to boil off or to evaporate from the wash, according to the first graph. But now that i've concentrated the ethanol to above 50%, they became tails material, bleeding into or at least shortening my hearts.

[Here i go on a rant for a bit:]

Show Spoiler

I can't handle instructions of the sort "Do it as i tell you, that's the way it's always been done, don't do it any differently and don't ask stupid questions!" well, i'd like to know why the instructions are what they are, it gives a lot more flexibility and room for improvement IMHO. Sorry for the rant, and this was not directed to any specific individual here, but at times i get the impression that curiosity and experimentation are frowned upon or their merits not understood by old-timers preaching their gospel (without telling how that gospel came to be).

My theoretical assumption though is, that no real world pot still will reach 1 theoretical plate (as in zero reflux), especially in the beginning of the run, due to passive reflux. But that is when we want the least reflux while stripping a mash/wash in order to get the isoamyl to bugger off! Hence my proposition to air it out - which should be done quickly i assume, so not as to give acetobacter and similar nasties too much of a chance to ruin the mash.

But as long one doesn't rely on shortcuts in every step of the process, perhaps it's all right.

I am certainly not trying to make any short cuts to getting a cheap headache fast, if i want that i'll go sniffing glue. But the information i got in this thread was very new to me, and now i'm trying to incorporate it into my work flow, so i can get an even better product.
Also i wanna say thanks for posting this info, for educating and enlightening me!

[Bagasso]

I was puzzled, though, to understand in which cases it made sense to cut foreshots during the first run, or even to make only one run overall. It's time I look for this information on the site without finding it, probably out of choosing the wrong keywords.

Could you elaborate or point me to some other thread where it is explained the different cutting strategies (two runs no cuts in the first, two runs cutting foreshots in the first, one run, three runs) for the different products (rum, whisky, brandy, Geist - or neutral)? A general logic framework.

You won't find it because this is probably the only thread where the high volatility of fusels in low ABV boiler charges is discussed.

The bold and underlined idea is why a fores cut is beneficial in the stripping run. Unless you water your low wines down to 10% ABV you will not have that situation again.

This mistake of mine was pointed to me also by Bagasso. So it's actually at the end of the distillation that I move away from the canonical behaviour toward the left of the Fig. 1 in the original post.
In fact what I should keep in mind is that, in the upper portion of the column, which is where I collect after all and so what matters to the home distiller, if the column is brought to equilibrium before beginning collecting, I always have the canonical situation until the end of the run.
In the final part of the run one collects fusel oils in any case.
Before this thread I would expect to collect fusel oils at the end of the run because they are less volatile.
Fig. 1 tells me I am collecting them now because I have a low-alcohol mix in the kettle at the end of the run, and in this situation fusel oils come up faster than at the beginning of the run. But the collected spirit wouldn't change because of this new knowledge! The cat catches the mouse in any case.

Not exactly. By the time the ABV of the boiler charge has shifted to the left significantly you will have reduced the higher volatile compounds because there is a small amount of them.

Also you seem to be mixing pots and columns. If fig. 1 is correct, in a pot with low ABV in the boiler, fusels come off first, contrary to canonical thinking, which is why a fores cut is a good idea even in a stripping run with a potstill.

In a column, the fusels drop as the ABV of the condensing vapor in the packing (probably even more pronounced in plates) rises in ABV. So that the system acts like the right side of Fig. 1.

[The Baker]

I have a couple of 20 litre pyrex containers that I will configure as a solar still one day. If I can figure it out and get around to it.
But it will work by evaporation, not by boiling. Or I expect so, it seems unlikely that the liquid will actually boil but it will certainly evaporate if I set it up right.

Geoff

[Bagasso]

I have a couple of 20 litre pyrex containers that I will configure as a solar still one day. If I can figure it out and get around to it.
But it will work by evaporation, not by boiling. Or I expect so, it seems unlikely that the liquid will actually boil but it will certainly evaporate if I set it up right.

You need to look up solar cookers. Basically an insulated box with a glass top to put your pyrex containers in that will help heat build up and the average ones get up to about 150°C (300°F).

[zapata]

I wont say I made a solar still, because that would be far too generous for what I did. But once upon a time I slapped some junk together as a proof of concept solar stripper. It took a few days waiting on the weather I guess, or because it wasn't tracking the sun, but did in fact work. A little bit while not boiling. And just slowly while boiling. Couldn't see the wash (jealous of those Pyrex vessels you have Geoff!), so I was judging boil by sound, or feel of the pot vibrations. When it wasn't boiling but was hot, maybe it would drip every so often. I assume any small amount of passive reflux was just holding it back from a slow sub boiling distillation.

I abandoned the project as cool but unsafe. Legally speaking, not as in physical safety. It was a still I didn't mind leaving unattended (is that blasphemy, even in this case?) But I had a freaking still up in my yard for days, obviously in broad DAYLIGHT. And it looked like a still too. Anyway, just encouraging words, the general idea is workable, and my experiment was far from optimal.

[The Baker]

Thanks, Bagasso and Zapata, very helpful.

Geoff

[der wo]

I always have the canonical situation until the end of the run.
In the final part of the run one collects fusel oils in any case.
Before this thread I would expect to collect fusel oils at the end of the run because they are less volatile.
Fig. 1 tells me I am collecting them now because I have a low-alcohol mix in the kettle at the end of the run, and in this situation fusel oils come up faster than at the beginning of the run. But the collected spirit wouldn't change because of this new knowledge! The cat catches the mouse in any case.

Normally you would finish the distillation before this point.
The % in the kettle is not the reason. The % one plate before the collection point is the reason. If there the % goes down, the fusel alcohols travel more and more up the column. But when you distill neutral alcohol and you are not able to hold the % high because it's not much alcohol left, you will stop the run. It doesn't make sense to push 5kw in a 3" column and collect every second one drop 95% alcohol. This is what you would have to do at the end of a run to collect the remaing ethanol without the fusels.
The low abv in the kettle pushes the fusels into the column, but the high abv in the column holds them in the downer part.

i thought potstill stripping was done because it's less of a hassle than refluxing, and i thought that no cuts needed be made, since a stripping run with reflux column would follow.

That's what I thought too. But perhaps I was wrong and it makes a difference to cut a few fores at the strippings.

My theoretical assumption though is, that no real world pot still will reach 1 theoretical plate (as in zero reflux), especially in the beginning of the run, due to passive reflux. But that is when we want the least reflux while stripping a mash/wash in order to get the isoamyl to bugger off!

Yes. As long the lid and the riser heats up, you have more than one plate. But normally (at least when distilling neutrals) you are still deep in the fores and heads when the riser is already heated up.