Why are people getting hooked on low temps?

[Hawke]

Why am I seeing so many post in which people are trying to distill at or near 78*C?
48 hour runs to recover about 10% of the available alcohol, maybe?
I'm new at this, so maybe I need to do some more research, as I've aparently been doing something wrong.

[rad14701]

It's not just you, Hawke, I've been noticing the same thing... I think the confusion is that people are assuming that if they keep the wash, or distillate vapor, at 78 degrees that things will work better - which is a mistake... While vapor temps should be in that range, wash temps need to be closer to boiling... The still is going to attain its own optimal running temperature based on several factors and forcing it to run at a pre-defined temperature is just a waste of time and effort...

Now, if we were talking about using a Charles 803 for making fuel ethanol, and it had an external boiler feeding it, that would be a different story... With the Charles 803 you DO want to keep the column temperature at 78 degrees, or thereabouts, and you use a water control valve and a condenser in the lower column to maintain this temperature... But most of us aren't making fuel ethanol with a Charles 803...

Seems to be just another wave of people driving the thermometer and expecting good results, only to be disappointed...

[trthskr4]

I don't think you're doing anything wrong, I think folks have the wrong idea about how to run a still (at least a potstill). The components of the mash will seperate at the temps that they're going to any way and as I've said recently on another post you can't force your still to do what it doesn't want to and expect to get good results. There's only so much alcohol in a wash and the fores and heads will come off at a certain temp range, then the hearts have their own temp range and of course tails will be at a higher temp range and those components will come off in the run regardless of what you try to force on the still. I think it's the same with a reflux still also but I could be wrong. Forcing the temps on a run will only get fores in the hearts and hearts in the tails and tails in the heads, etc. by running too slow or too hard. That sounds right in my mind anyway.

[libertyesq]

Well said truth. I agree with you 100%.

[Usge]

A potstill will run it's course as mentioned on its own, holding at various temps as it goes but increasing in vapor temp as the amount of alc remaining reduces until it reaches parity (or water vapor) at 100c.

This relationship in theory is based on the fact that alc and water separate (vaporize) at different temps—pure Eo2 will vaporize at 78C vs water that vaporizes at 100c. The higher the abv of the solution you are distilling, the lower the temp will be that it starts to come off and visa-versa. Another way to look at this relationship is that as you distill, regardless of how fast or how slow you are doing so, the amount of alc in the solution/pot will decrease at a faster rate than the water solution will —but slows when it nears parity. Which means...(the abv of the liquid in the pot is constantly lowering as you go). There's a whole lot of different angles to look at this one princpal...but I've found this chart from the Theory section of the main site really helps.



The curve here is the relationship of the various stages of separation between a water and alc solution from the range of pure water vapor (100c) to pure alc (78c). It's a theoretical chart...so It's going to have an increasing skew error towards pure alc the more inefficent your still is. But, it's really useful visual aide in understanding the basic princpal about the relationship between abv/volume/ and temp.

Here's another angle to look at this in theory: 10 gals of 4% abv and 1 gallon of 40% abv...both contain the same amount of alcohol—even though both would begin separating from the water at entirely different temps.

[heynonny]

This temp business: I have a thermometer in my wash, not so much for actual temp (as long as its below 100) but for how fast it (temp) rises. I also have a probe at over-the-top for the same reason, , , , heynonny
(my two cents worth, $1.00)

[Usge]

Temp in the pot is only useful for mashing...not distilling. Temp in vapor path at the top can give some indication of what's going on (although they usually vary a lot from still to still and differ by too many factors to be useful by way of comparison).

[Hawke]

Guys, I have to admit that this was a retorical question on my part. Hopefully all of your great replies will get these new people on the right track. Or maybe just back to thier info source to read the rest of the story.

[heynonny]

"Temp in the pot is only useful for mashing...not distilling."

Actually if temp is going up fast (the gauge would show) (I use a big propane burner) I (can) turn down the heat quickly, and near end of run when temp hovers at 99 deg I am VERY careful with increasing the heat, , , , neynonny

[tracker0945]

Oh no! not the makings of another thermometer in the still discussion is it?

Cheers.

[Hawke]

God, I hope not Tracker,
I was trying to get people off the 'want to set the controller at 78*C' mentality. That might work on a Charles 803, but it just don't cut it for stillin' drinkin' likker.

[Nik Onay]

If I didn't let my washes get above 78 degrees on a stripping run, nothing would ever distill. It takes to about 87 degrees for anything to even start. If you were just distilling ethanol, it would work at just 78 degrees, but since it's mixed with water, the temperature of distillation will be between the boiling point of ethanol and water. If there is a greater percentage of ethanol than water, the boiling point of the mixture will be closer to that of ethanol ( 78 degrees) and if you have a greater amount of water than ethanol ( like a 10% wash) then the boiling point will be closer to that of water ( for me it's from 89-92 degrees). It doesn't really matter what the temperature is when you distill as long as there is distillate coming over. When I made my still I made a hole in the pot for a pot thermometer and put in a head thermometer just because I used to work in a pharmaceutical plant and that's how we did it there. But anymore I just plugged the hole in the pot and I use my thermometer as a plug in the distillation head. To me, the correlation between temperature of distillation and taste of heads and tails is pretty loose. If I used temperature to judge when heads and tails came out, it would always taste bad.


I haven't seen anybody talking about distilling at only 78 degrees. They could be doing these long boils at 78 degrees to get rid of all low boiling compounds. Methanol boils at what, 56 degrees or something like that. A long boil at 78 degrees would probably ensure that there is no methanol and most of those low boiling aldehydes in the hearts when you raise up the temperature. That's the only thing I could think of. I can't think of any other reasons.

[pintoshine]

Is there a chance that there is some confusion here? My column still, which makes 95.4% never gets over 78C at the head but the boiler goes from 85 to 100 during the run.
My pot stills will go from 90 to 100 during a run. SO I am wondering if you are seeing people trying to bring their columns to equilibrium and thinking they are talking about pot stills?

[Hawke]

Pinto,
The ones I was speaking of are the ones with electric elements, trying to use a t-stat to maintain 78 to 80*C. Doesn't work for a column anymore than it would for a pot as any disruption of heat will cause the fractions inside the column collapse. The only still I know of that uses column temp control such as this would be the Charles 803. (Which uses a remote boiler)

[pintoshine]

Oh yes, I know exactly which one you are talking about. I had one wear me out about a PID a short while back because of a complete lack of understanding of partial pressures or even the phase chart that is so popular. The only thing I can say is that some won't accept the fact that miscible mixtures generally boil at a temp between the two boiling point and will not boil one without some of the other. I argued this point about methanol and water and ethanol a while back and never did get the stubborn ass to realize that if you start with methanol in the wash then it is going to be present, in decreasing amounts, throughout the complete run and does not favor the heads, just the same as the ethanol will come over during the whole run, in decreasing amounts, and does not favor and one temperature range.
When the find that they get little to no output they will try something else. Sometime we just have to let children learn on their own. No matter how many times you tell a child "careful, it's hot" they will have to find out for themselves. It is human nature sometimes.