Pot Still Heating Rate

Putting older posts here. Going to try to keep the novice forum pruned about 90 days work. The 'good' old stuff is going to be put into appropriate forums.

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g0dsmack
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Pot Still Heating Rate

Post by g0dsmack »

I have read many of the intro threads and I have just finished the first run on my still and have a few questions about heating rates since I couldn't find anyone ever calling it out specificly.

Between what I remember from school and what I have read on the forum, here is my knowledge dump: (Please correct/excuse my jargon and any statements)

1) Start with LOW heating rate up to the begining of boiling to allow good seperation of foreshots.
2) Watch out, a HIGH heating rate can burn any lees (solids) that make their way into the charge of the still, giving a bad burnt flavor (not learned from experience... yet)
3) The temp of the boiling charge in the still is (mainly) dependent on the ABV% in the liquid
Side Note: Boiler temp is also dependent on a few other things like atmospheric pressure and other compounds in the charge, but monitoring boiler temp is not advocated on this forum (use your senses, smell, taste, and sight to monitor your distillation)
4) Increasing the heating rate to the still will not increase the temp of the liquid charge in the still.
5) The increased vapor flow will cause less internal reflux (condensing inside the still/column/head vs condensor and flows back into the pot) causing a lower ABV% in the distillate
6) As long as your condensor can handle the heat load from condensing the vapor, you can increase your heat load to the still, ultimately increasing your stills output (dripping vs streaming out of the coil)

If everything above is correct, my question is for a wiskey or rum run would I want to have a lower or higher heating rate?
Usge
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Re: Pot Still Heating Rate

Post by Usge »

g0dsmack wrote:I have read many of the intro threads and I have just finished the first run on my still and have a few questions about heating rates since I couldn't find anyone ever calling it out specificly.

Between what I remember from school and what I have read on the forum, here is my knowledge dump: (Please correct/excuse my jargon and any statements)

1) Start with LOW heating rate up to the begining of boiling to allow good seperation of foreshots.
All my answers here are going to be related to "potstilling" for whiskey or flavored drink. Start with HIGH heat..till you pot starts to rumble (come to a boil). THEN turn it down to low heat. Otherwise, you are just wasting time (take forever to heat large volume of liquid up to boil on low-heat). Yes, you want low heat when it starts "dripping" distillate. But, until then...get on with it! hint: use of boiling chips in your boiler (small pieces of copper) will not only help break up your boil so it doesn't overheat/superheat, but will signal to you audibly when your pot is getting to a boil.
2) Watch out, a HIGH heating rate can burn any lees (solids) that make their way into the charge of the still, giving a bad burnt flavor (not learned from experience... yet)
This is true. In general, you want to watch/control the heat you are putting into the still after things get going. The less heat you run, the more things will tend to separate and the distillate flow rate will slow. The more heat you push, the faster things will go and the more it will tend to blend/smear together. This can be bad or good just depending on what kind of flavor (or not) you are looking for. Push heat far too hard, and you are going to pull tails all the way through the middle.

Every still is a little different in this regard to how it responds..which is why you don't see any hard fast rules for such things. But, you can start this way....once your still starts dripping under low-heat...leave it low..dripping..till you collect your foreshots. (about 150-250ml per 5 gals of wash/mash). Then, tick up the heat just till you see it break into a single thread/stream. Back the heat down and it should dribble fast. Bring it back up..to find the stream...and there's your flow rate to use as a starting point. From there, use your taste. If you want it more blended add heat. If you want it more concentrated, lower the heat. If you are single running wash, you are probably going to end up running it slower than if you are on a 2nd run.
3) The temp of the boiling charge in the still is (mainly) dependent on the ABV% in the liquid
Side Note: Boiler temp is also dependent on a few other things like atmospheric pressure and other compounds in the charge, but monitoring boiler temp is not advocated on this forum (use your senses, smell, taste, and sight to monitor your distillation)
Yes, but you are missing the point. It "also" means you can't control the abv of the "vapor" coming off either. That's also determined by what's in the pot. The boiling point of any 2 liquids is somewhere in between the boiling point of the 2 mixed. So, if ethanol boils at 172F and water at 212f..then the boiling point of a mixture of the two will fall somewhere in that range. The higher in concentration of ethanol it is...the "closer" the boiling temp will be to that of ethanol. The more water (or the lower the concentration of alc) the closer the boiling temp will be to water. This is why as your run progresses, the boiling point is constantly changing (getting higher) as the alc in the pot is depleted. THIS, is why it's pointless to try and measure the temp on a potstill — its determined by the starting abv in the pot, and then constantly rises as the alc is depleted). It's also a key point to remember is...that the "boiling" point we are talking about..is the vaporization point (ie., the point at which the vapor will rise and flow out your stillhead towards your condenser. Capicé?
4) Increasing the heating rate to the still will not increase the temp of the liquid charge in the still.
Increasing the heat will make the vapor/distillate come out faster. You'll therefore be depleting it from the pot faster and the temp will rise faster. Not to mention you'll be blending/smearing the compounds/fractions together more. (which may be bad or good, depending upon what you like, are looking for, etc. )
5) The increased vapor flow will cause less internal reflux (condensing inside the still/column/head vs condensor and flows back into the pot) causing a lower ABV% in the distillate
Having a discussion on internal reflux is rather pointless in the context of a potstill. There is very little reflux that occurs naturally inside a typical potstill. So, lets not worry about this for now at this point in the discussion — it will just confuse things. You can read more on reflux, compound reflux later. Lets stick with potstills for now. They are what they are.
6) As long as your condensor can handle the heat load from condensing the vapor, you can increase your heat load to the still, ultimately increasing your stills output (dripping vs streaming out of the coil)
True. But, as was said before in answer to an earlier question....the faster you run it, the more it's going to smear things together. The slower you run it, the more it will tend to separate things (although never cleanly). This is how you fine tune your particular potstill to "taste" so to speak. And it's the intangible part of knowing how to run one. (controlling the heat).
If everything above is correct, my question is for a wiskey or rum run would I want to have a lower or higher heating rate?
Alrighty then! Lets say you just want to do a stripping run, to reduce the volume of your wash, blend all the flavor you can together, and prep it for a 2nd run through. How you think you would run it?

Now lets say you gonna do a final spirit run...where you are going to be running off fresh wash/mash or stripped low-wines, how you think you gonna run that?
g0dsmack
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Re: Pot Still Heating Rate

Post by g0dsmack »

That all makes sense to me. Run a higher heat load if I am going to do a stripping run and low if I am doing a final run trying to get clean cuts. I feel ready for round two with Birdwatchers, and this time maybe I'll do a stripping run first and see if I can tell a difference in the final product. Thanks, your input sure makes me feel a lot more at ease with my heat controls.
Having a discussion on internal reflux is rather pointless in the context of a potstill. There is very little reflux that occurs naturally inside a typical potstill. So, lets not worry about this for now at this point in the discussion — it will just confuse things. You can read more on reflux, compound reflux later. Lets stick with potstills for now. They are what they are.
The reason I brought reflux up is because I run a keg (15.5 gal) pot with a 40" packed tower with reflux for neutral washes (which is what I first ran), when I move to wiskeys I will put my 20" tower w/o packing or reflux. My first 5 gal batch took me about 5 hours to distill out 1 gal. I numbered a bunch of 250 ml jars and lets just say the cuts are very clean. I can definately smell and taste the difference between the heads, hearts, and tails. I guess the next trick will be do my cuts based on what is actually come off the still vs going back through and figuring it out.

Practice makes perfect, looks like I know what I am doing the next few weekends! Ferment on Monday, Distill on Sunday... kinda has nice ring to it, maybe Ill carve something up for the garage.
BigDaddy33
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Re: Pot Still Heating Rate

Post by BigDaddy33 »

by far, the best info i have read on this site. thanks
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ranger_ric
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Re: Pot Still Heating Rate

Post by ranger_ric »

Jolly Good Post... Everything put in 1 concise place...

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InglisHill
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Re: Pot Still Heating Rate

Post by InglisHill »

Should sticky this stuff!
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