Do I need a thermometer on my pot still?

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Do I need a thermometer on my pot still?

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

------MOD EDIT------
This thread is select posts from a rather lively discussion about the need (or lack thereof) for a thermometer in a pot still. If you read through, you'll see that we all have varying opinions about this. In summary, it is not essential, and in order to become a good distiller you should be capable of running a pot still without any instruments at all (alcometer, thermo, etc). However, sometime it can provide extra information about run progression etc that can be useful. It is probably best considered an optional extra.

The one thing almost everyone agrees on is that you shouldn't use a thermometer to make cuts on a pot still - use your senses.
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Original discussion here: viewtopic.php?f=16&t=12791
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New discussion thread started here: viewtopic.php?f=68&t=43026

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.
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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 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 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 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 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 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 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 theholymackerel » Tue Dec 08, 2009 7:44 am

CletusDwight wrote: 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.


OK.

So yer usin' yer thermometer to make cuts. Fine. How did ya decide at what temp to make the initial cut that yer thereafter copyin'?

See? The original decision where the cuts lie was still a decision that came from yer nose and tongue.

Anyone that consistantly turns out good spirits from a potstill does so usin' their sense of smell and taste. Science can't can't design a tool to make cuts that can even come close to my God-given sense of smell and taste.


If yer usin' any sort of gauge on a potstill 'cause it gives ya a calm feelin' of controll, that's just fine. But it's not necessary, and lets not try and force the new guys to think they must do it this way. As many many experienced distillers have already stated in this thread: they started with a thermometer on their potstill 'cause they thought it was necessary, only to find out later after competency was gained that it was un-needed and made for one more hole in the system to have to seal up.
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Re: Thermometer on a pot still?

Postby blind drunk » Sat Dec 12, 2009 7:28 pm

The thermo's been reading 80 degrees solid but I've collected a bunch of nasty heads and a bunch of 500 ml jars that all taste different,


That's odd. Temp on my pot still rises continually through the run.


Mine rises too. I was trying to say that at 80 degrees I collected a wide tasting range of jars. So if I went just by temperature alone, I would have missed the subtle flavour differences when my pot was at 80 degrees, which it hovered at for a couple of hours. In other words, at 80 degrees, the range in smell and flavour was significant enough to make distinct cuts which I would have missed if I went by thermo alone. Cheers, bd.
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Re: Thermometer on a pot still?

Postby HookLine » Sat Dec 12, 2009 9:10 pm

my pot was at 80 degrees, which it hovered at for a couple of hours.

Temp on mine just climbs slowly but relatively steadily (after it hits boiling). Certainly never sits at one temp for two hours. Maybe you had a lot of heads in that charge.
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Re: Thermometer on a pot still?

Postby blind drunk » Sat Dec 12, 2009 9:27 pm

Maybe you had a lot of heads in that charge.


It was a 26 liter charge of UJSM low wines. I got about 7 liters of heads so far. I'm just airing out the rest but I'm guessing there will be more heads to add to that early count. I sure wish could get through those heads quicker though. bd.

edit - closer to 24 liter charge
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Re: Thermometer on a pot still?

Postby Usge » Sun Dec 13, 2009 11:37 am

I have therms on all my potstill heads. I started on a little 5L copper alembic and I had a therm installed right at the top of the lynearm before it goes down. That was probably the most accurate therm I've had in terms of it's relationship to the theory section of this site. And it helped me immensely starting out...to see what was going on..and have "some" idea what to expect. It also helped me in learning/understanding the basic theory/relationship and how things were connected. (ie., a certain % wash...would start coming off at given temp, at a certain %). And, the understanding that I could work that from different angles..and start with a percent abv I "wanted" ...to what % abv the still charge should be to get there...although it's much more difficult than it sounds...given you don't know exactly what you'll be keeping for "hearts" to blend. It only gives you an idea of where it will "start" coming off. The rest is an estimate. My other 2 heads on my 5 gal pot from the Colonel...the therms are pretty useless other than just a general idea of when the vapor is starting to heat up/rise. They aren't nearly as accurate.

But, in the end, as someone's sig around here used to say......"I ain't never seen no thermometer with taste buds". And I'll add to that...that I've never seen a hydrometer with taste buds either. I've pulled tails at 77% before. I'd have never known that unless I was tasting/smelling what was coming out of the still. While a hydrometer is a more reliable way to measure abv, that in and of itself is also not going to really know whether what you have in the jar is heads or hearts or tails either. It can give you an "idea"...based on where you are in a run. And it can do that more reliably than "most" therms can. But, you still have to taste and smell what comes out. You have to do that to "learn" as well (smell/taste). And the point here is not just to learn the theory of why all this works...but to learn how to apply it/use it. And that takes time (trial and error, practice, experience). And just as there are people here who's experience has been that their hydrometer bobs just before tails on their particular still or etc...there are people..like myself..who've experenced runs using temp that were just as informative and even accurate in their predictions — that's acknowledging that in general, hydrometer readings and their temp based variances are generally a more stable reading overall because of a smaller possible variance scale.

I have nothing against the use of any or all of these things...and I use everything. But, when it comes down to what goes in my blend jar and what gets recycled...that is based exclusively on me and nothing else. As far as the main site goes....it's there to help people learn. When you start out, and you wouldn't know the difference between heads and tails if you bit you on either one.....it's often the recommendation to find "other" ways to make a cut that is NOT dependent upon having experience in taste/smell (ie., cut from 80% to 70%)...so that you can start to learn..unltimately about what you are dealing with. There isn't anyway to just give someone "experience" to know the difference the day they walk through the door. The ultimate goal here is to use all the resources made available to develop your own experience as safely and effectively as possible. The other side to that to keep in mind is...the history of making spirits is long. And there has been plenty of exceptional whiskey, etc., made in this world WITHOUT the benefit of understanding some of the technical and theoretical nuances that are printed there in the main section for anybody to read. So, keep in mind the goal...and that is to make exceptional product that "you" like, safely....at home.

I'll leave off with this..I made the same observations that some of you have here...that temp is part of theory, and why would it not be something you could use, etc., etc. And it "is" all of those things. But, I also got "stuck" for months...doing runs mechanically, without learning a damn thing other than the results were not consistent or what I wanted. One time..a cut from 80-70% was fine. The next time..it wasn't. But, as far as the therm and the hydrometer was concerned...it was the "same". It's missing the forest for the trees kind of thing (while still understanding that the trees are what makes up the forest and one cannot exist without the other). So, use whatever helps you understand, learn and get down the road...it is useful. But, it's not a replacement for experience in tasting/etc...and never was. You'll gain that by doing it...over and over and over. And experimenting as well.
The main concern is that we all do those things (experiment) safely — which is exactly why it's important to understand how these things work and why you don't put a valve on the output of a potstill.
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Re: Thermometer on a pot still?

Postby Dnderhead » Sun Dec 27, 2009 10:08 am

I whould think in the head of the of the thumper, but no matter where you put a thermometer in a pot still
its going to be as handy as a pockit in your underwear. learn to make cuts by taste and smell.
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Re: Thermometer on a pot still?

Postby Hack » Sun Dec 27, 2009 11:04 am

A thermometer on a pot still is only useful in a general way. Simply put, it won't give enough accuracy to be able to rely on it to make cuts. It will tell you the temperature of the vapor in the column, and from this you can infer the alcohol content of the vapor. However where to make the heads and tails cuts from this will vary depending, on the starting abv of the wash in the boiler, and how hard you are running the heat, add a thumper to this and it gets more complicated. If you still feel you need a thermometer and are using a thumper, put it on the column of the thumper. If it was me, I'd leave it out and focus on learning how to make cuts by taste and smell. Making cuts by taste and smell is the most reliable method and works no matter what because it eliminates all the variables of what's going on with the still and the wash. There is good information on how to do this in the stickys in the novice section. One of the best is the first post in the "distilling advice" stickie.
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Re: Do I need a thermometer on my pot still?

Postby myles » Fri May 03, 2013 11:47 pm

I like to use a thermometer and a parrot in combination, and there are two very specific uses for the thermometer. My thermometer goes at the high point in the vapour path, and is used for the following because it is convenient to do so.

1. When the vapour temperature hits 84 deg C, I close the lower by-pass valve on the parrot, or put the parrot into the distillate stream. This minimizes the amount of heads going into the parrot. I don't want the very first stinky heads contaminating the parrot.

2. When the vapour temperature reaches 98 deg C, I switch off the power input to the boiler - but leave the condenser running.

Between these points I depend on making cuts by ritual, but the hydrometer gives me a bit of advanced warning that changes are imminent, so I can change the volume of the cuts taken. Pint volumes between the transitions and just an ounce or so for the duration of the transition.
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