Thermometer on a pot still?

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Thermometer on a pot still?

Postby Pamulli » Fri Dec 04, 2009 7:09 am

Maybe this should be in the novice section, but since it is design related, I thought I'd post it here.
I'm building my first pot still out of a stainless milk can and wanted to know about incorporating a thermometer. I don't see thermometers in a lot of pot still pictures I've seen on here however it seems like it would make it easier for a newbie to have one? If I do want to put one in, does it matter where? Can I put it in the top of the milk can or does it need to go in the column or does it even matter?

Thanks for the advice
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Re: Thermometer on a pot still?

Postby CletusDwight » Fri Dec 04, 2009 7:31 am

Yes, yes and thrice yes.

It's possible to manage without one if you are experienced in making cuts by taste and smell.

It's possible to manage without one if you have a hydrometer that measures abv (not a brewers type, an alcohol-meter type)

But other than that, without one, you're flying blind.
Measuring the temperature at the point where the vapour begins to condense tells you exactly what the vapour composition is. (There's a 'Distillation Temperature and Concentration Relationship' graph on the parent site - theory section I think.)

Until you can tell by taste, the composition is a good guide to where to make your 'cuts'. And when to stop collecting tails and turn off the still.

It matters where you put it because it tells you what the composition is at that point. Might not be what/where you're collecting. You can get it right by doing a calibration run using plain water - boils and condenses at 100C exactly.
Best place is likely to be at the highest point - where the vapour is taken off to the condenser.
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Re: Thermometer on a pot still?

Postby Aces High » Fri Dec 04, 2009 7:39 am

yeah all these guys say they dont use it, but personally I find it quite handy both for seeing when the wash is coming up to temp, and also for logging ABV's and how they relate to degrees. You dont need it, but you will learn a lot more about how a wash performs if you have one
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Re: Thermometer on a pot still?

Postby LWTCS » Fri Dec 04, 2009 7:40 am

Prollem is,

2 or 3 runs into your career as a hobby distiller, you'll never use it again (with your potstill).
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Re: Thermometer on a pot still?

Postby Pamulli » Fri Dec 04, 2009 7:49 am

Thanks for the posts...I'm ok with installing one even if I only look at it at first if it will help me. Just to clarify, if I'm going to have a thermometer, the best location would be at the top of my column where it bends and goes off to the condenser?

Thanks again for the advice
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Re: Thermometer on a pot still?

Postby CletusDwight » Fri Dec 04, 2009 7:55 am

That's an affirmative Pamulli.
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Re: Thermometer on a pot still?

Postby Pamulli » Fri Dec 04, 2009 1:39 pm

Is there a good way to attach the thermometer to the top of the column? In looking around I mainly see thermometer with long Stainless steal probes, which don't seem like you could easily attach and get a seal?

Thanks
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Re: Thermometer on a pot still?

Postby Pamulli » Fri Dec 04, 2009 2:31 pm

I found some dial thermometers that have a threaded connection with a 2.5" probe so I assume I can tap the top of the column and just screw it in. Should be simple enough.
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Re: Thermometer on a pot still?

Postby blanikdog » Fri Dec 04, 2009 3:43 pm

If you put some form of boil breaker, ie, bits of brokem porcelain or copper, even small quartz pebbles you can tell by the sound how the boil is going. I still have a thermometer in my kettle but never use it. I guess it's nice 'eye candy' as someone said to me a long time ago. Do it if you wish, the choice is yours.

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Re: Thermometer on a pot still?

Postby Hawke » Fri Dec 04, 2009 5:01 pm

If you use the screw in dial type, just get a 1/2" female copper to pipe fitting. Drill the apropriate size hole and solder it in. If you use a probe type, drill an 1/8" hole in an old wine cork and the apropriate sized hole in the column.
I made two runs on my first potstill with the thermo, after that I just stuck a cork in the hole. The last two potstill heads don't have the provisions for a thermo.
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Re: Thermometer on a pot still?

Postby HookLine » Fri Dec 04, 2009 9:16 pm

I find a thermometer very useful in pot stilling. Never used a parrots beak.

But you also need to be able to run the still without any instruments as well.

And make your final cuts with taste and smell, not temperature or % abv.
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Re: Thermometer on a pot still?

Postby rubber duck » Sat Dec 05, 2009 11:36 am

In my opinion it's not necessary to have one unless your completely ocd like me. I don't use my termo to run the still, but I record my temp through out the run. I like to keep crazy good notes.

It's kinda like a tacometor on a car, you don't realy need it but one day you might.
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Re: Thermometer on a pot still?

Postby big worm » Sat Dec 05, 2009 4:46 pm

i built a thermo well on mine, so i either use it or have to make a plug in it. it can be useful while learning how to drive your rig. watch the temp start to rise up while heating up. while stripping mine will run about 200-204 deg depending how hard i push. as the run gets longer the temp rises because more water is being carryed over with the etho by the time it gets up around 208-209 deg its just about thru coming off around 20% or lower. it will help you to understand whats going on but thats about it. you can tell when its getting hot by touching it....or know about when to stop by smell/taste/sight. get a good digi and have at it....like blank says it looks like eye candy :lol: .....blannnnkkkkkk
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Re: Thermometer on a pot still?

Postby goose eye » Sun Dec 06, 2009 4:56 am

somethin to break off tryin to hide it in a hurry

so im tole
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Re: Thermometer on a pot still?

Postby Hack » Sun Dec 06, 2009 10:28 am

I've never put a thermometer on my pot still. After your first couple runs you'll see it isn't needed or all that useful.
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Re: Thermometer on a pot still?

Postby theholymackerel » Sun Dec 06, 2009 11:55 am

A thermometer gives someone new to distillin' somethin' to look at while they are tryin' to figure out what the hell is goin' on, but it doesn't give any useful info. Thermometers, in and of themselves, aren't that bad, what's bad is the hole in yer boiler that you'll kick yerself for every time ya look at it in the future.
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Re: Thermometer on a pot still?

Postby CletusDwight » Sun Dec 06, 2009 12:36 pm

Well, seems like I wuz wrong. :oops:

Better go and rip that thermometer out of my still.
Then I'll go down and rip the speedo outa the car - don't need that either, or the fuel gauge....
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Re: Thermometer on a pot still?

Postby Hack » Sun Dec 06, 2009 6:40 pm

CletusDwight wrote:Measuring the temperature at the point where the vapour begins to condense tells you exactly what the vapour composition is. (There's a 'Distillation Temperature and Concentration Relationship' graph on the parent site - theory section I think.)

Until you can tell by taste, the composition is a good guide to where to make your 'cuts'. And when to stop collecting tails and turn off the still.


The temperature is relative to the percent alcohol in the vapor and on a pot still this percent is also relative to the starting abv of the wash you are running. Yes it will rise as you go through the run and the percentage of alcohol in the vapor goes down, but it's not going to give you any predictable numbers to make cuts by because it also varys with the starting abv of the wash. Unless you are running the exact same wash every time the temp where you want to make your heads and tails cut will vary. This means its smarter and easier to just learn how to make cuts by taste and smell because that will always be right no matter what recipe you're cooking.
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Re: Thermometer on a pot still?

Postby goose eye » Mon Dec 07, 2009 4:22 am

cletus you putin the same value on a tempeture gage on a pot still as you do a fuel gage in your truck.
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Re: Thermometer on a pot still?

Postby WalkingWolf » Mon Dec 07, 2009 4:46 am

I think what poor Cletus is trying to point out is -- neither the temp gauge nor the fuel gauge are worth a darn cause the fuel gauge in the truck don't work no how :wink:

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Re: Thermometer on a pot still?

Postby CletusDwight » Mon Dec 07, 2009 11:25 am

OK, lets take this a bit slower.
I've been tole off fer bein sarcastic - fair 'nuff. That was a mite below the belt.

Yes, I agree that an expert distiller should be able to run his/her still on taste and feel alone. No arguin with that.

What I will argue with (and I'll use any verbal weapon if need be) is the idea that someone who comes for swimming lessons should be told there ain't no other way than to go and jump in the deep end with a lead brick tied to his ankle.

When you've never run a still before, you gotta have something to hang your hat on. Otherwise all you've got is stuff dribblin' out the end of the pipe and no idea what it is.

I use a thermometer in my still head because it warns me when things are coming up to temperature at the start and tells me what the current abv is during the run more accurately than a hydrometer.
Hack pointed out it's only really useful if you run the same wash time and again. That's true Hack - but that's exactly what I do. I keep careful notes on washes - every run is carefully logged. When I change to a different wash I start a new set of data. I can go back and remind myself about where the tails will come in, how far I pushed it before and how it worked out.

Somebody starting out needs to do that. Run the same wash over and over until he/she can tell simply by the smell of it, whereabouts it is.
Then they can maybe throw away the thermometer. But I ain't about to do it - I don't know enough yet.
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Re: Thermometer on a pot still?

Postby theholymackerel » Mon Dec 07, 2009 1:20 pm

CletusDwight wrote:I use a thermometer in my still head because it warns me when things are coming up to temperature at the start and tells me what the current abv is during the run more accurately than a hydrometer.


What makes ya think a tool designed to measure temp will give a more accurate measure of ABV% than a tool specifically designed to measure abv%?

I won't argue that a thermometer will tell ya when yer boiler is gettin' up to temp, but I can get the same info by lightly touchin' my lyne arm and it doesn't require a hole in my boiler. Boilin' chips don't require a hole either, they warn about imminent boil, but ALSO smooth out the boil AND inform ya of how hard the boil is.

So what useful info are ya gettin' from yer thermometer that makes the hole in the boiler worth it?
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Re: Thermometer on a pot still?

Postby blanikdog » Mon Dec 07, 2009 7:01 pm

Cletus, I understand where you're coming from. I have a thermometer on my still cos I thought it was essential. I was misled by confusing a pot still and a reflux still. The thermometer is still there to fill up the hole and for no other reason.

Sure, it gives you an idea of what's happening as the boil is approaching, but that's all it's good for. A handful of boiling chips - I use porcelain, but copper pieces are better as I've just learned - will do it probably better than a thermometer. You can hear the rattle as the boil begins, and you can adjust the temperature by the sound. I really does work and you can keep an eye on everything - so to speak - without looking. :) I know I've said all this before, but it's worth repeating. Holy is quite correct.

Nobody is putting shit on you, we're just trying to help. Temperature on a pot still will not tell you the abv. You need an alcohol hydrometer to do this.

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Re: Thermometer on a pot still?

Postby Hawke » Mon Dec 07, 2009 7:22 pm

As we can see, thermo and alco-meter use can almost become a religion. They both have thier place in the learning curve, but most master distillers can tell ya what's what by sight and smell, before they ever taste it. (At least the few I've met)
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Re: Thermometer on a pot still?

Postby kiwistiller » Mon Dec 07, 2009 7:47 pm

I barely measure with anything these days, except with a alcometer to decide when to stop. As I understood it there is a direct relationship between the abv you're pulling off and the temp? If thats the case then I can see the advantage of temp over alcometer as an indicator. I have two alcometers that read about 5% different from one another, and certified instruments are expensive. testing a digital thermo for accuracy is easy, and they're pretty reliable.

I wouldn't mind a thermo in the boiler to tell me ABV remaining in the wash, either.

That being said, either is just a crutch at best when it comes to cuts, and as it stands I have neither a parot or a thermo. :)

Just my two cents, shutting up now :lol:
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Re: Thermometer on a pot still?

Postby HookLine » Mon Dec 07, 2009 8:13 pm

As I understood it there is a direct relationship between the abv you're pulling off and the temp?

There is a direct and fixed relationship between vapour temp and abv. Basic physics.

Given that you know the basic composition of the vapour (ethanol/water), then knowing the vapour temp will tell you its abv, and vice versa, knowing the abv will tell you what temp the vapour is.

You do need a phase diagram to read off the abv from the temp. But you also almost always need a temp correction table when using an alcometer. So one way or another you are using a reference chart of some kind.

One big plus of thermos is that they can be used for over temp alarms (the programmable electronic ones anyway).

As far as running a still goes, I regard both thermos and alcometers are just useful tools, that give equivalent information (abv/temp). They should not be used to make the final cuts. That should be done with smell and taste.

Main thing I use thermo for is an extra warning for the boil up and end of run points, as a general guide as to where I am in the run, and for an over temp alarm.
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Re: Thermometer on a pot still?

Postby CletusDwight » Mon Dec 07, 2009 11:29 pm

theholymackerel wrote:What makes ya think a tool designed to measure temp will give a more accurate measure of ABV% than a tool specifically designed to measure abv%?

The fact that you need to float the hydrometer in a quantity of liquid. That means that the measurement you take is an average over however long it took to collect that amount. Especially at the start and end of a run, the composition changes rapidly and a thermometer is a better spot measurement.
theholymackerel wrote:So what useful info are ya gettin' from yer thermometer that makes the hole in the boiler worth it?

We're not talking about a hole in the boiler. There's no point in putting a thermometer in the boiler. The useful measurement is the vapour temperature where it begins to condense. Mine is in a 'T' compression fitting in the pipework. If I ever want to I can remove it and fit an elbow instead.

Some people are getting heated with me for arguing. Blanik - I ain't never said anyone's 'putting stuff' on me.
I'm trying to make a cold logical point.
There's an old saw that if you can't put a number to something you can't rightly understand it. When I come to make notes, it means a lot more to me to write down a temperature/abv reading than just sit sniffing at samples. Looking at time/volume temperature graphs has told me a lot about what's going on. Without the insight that data gave me I'd still be fumbling around without a clue.
I don't see why anyone should deny themselves the use of a valuable tool just because someone else manages without.
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Re: Thermometer on a pot still?

Postby olddog » Tue Dec 08, 2009 12:12 am

[quote=
I don't see why anyone should deny themselves the use of a valuable tool just because someone else manages without.[/quote]

You can't argue against that

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Re: Thermometer on a pot still?

Postby blind drunk » Tue Dec 08, 2009 12:25 am

That means that the measurement you take is an average over however long it took to collect that amount. Especially at the start and end of a run, the composition changes rapidly and a thermometer is a better spot measurement.


Good point, that's why Ian Smiley says you should get a tall and slender glass tube that barely fit the proof hydrometer. It's more accurate than just a jar.

BTW I have a thermo, hasn't hurt me but hasn't helped me neither. But it's there, waiting to be understood. Cheers, bd.
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Re: Thermometer on a pot still? Re: Why not?

Postby FAROM » Tue Dec 08, 2009 12:56 am

Use the thermometer is very useful, I always used three thermometers, one in the boiler, a low point in the column and one in the head column.
This way you control the evolution of the distillation process :D .
With an instrument of control over one has more advantages.
The information of the thermometer should be used together alcoholmeter, taste and smell. ciao a tutti.
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