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Measuring Mash Temps

Post #1 made 9 years ago
by Jomay
Hi All

Had about 6 BIAB sessions. All have gone reasonably well, no disasters - yet ;) although I have had a few mishaps and made a few mistakes, all the beers I have made have been well drinkable.

One thing that really irritates me is measuring the temperature of the mash water and the actual mash itself. I am using a ss 50 litre boiler with a tap and ss hop filter on the side, and heated on the bottom with a propane burner. Currently I am using an spirit thermometer to measure the temperature, and what annoys me is that it takes forever to get a reading. By the time it has stabilised I feel that its been so long that I really ought to stir it some more and get another reading. So my question is what do the rest of you do?

I have thought of buying an electronic gismo, but would that be any quicker? I suppose I could leave that in the water/mash, something I dont do with the glass one as I am afraid it might get broken.

Thanks for any replies, I am based in the uk - Jomay
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Post #2 made 9 years ago
by meryvn
I've got a cheap amazon thermometer (this one -> https://www.amazon.co.uk/Eddingtons-Dig ... hermometer ), i did also buy a ThermoPro TP10 one that i left in the boil but i think the probe has died on it as it now reads my fridge temperature at ~20°C.

I no longer leave my probes in while boiling as i think the steam gets in to them and ruins them, though i still do it while heating for the mash and during the mash, though take care not to let the probe sink.

Post #3 made 9 years ago
by Jomay
Crikey that was quick Mervyn.

Not really bothered about the boil, its the mash where temps are more critical. One of my errors/mistakes in my past efforts has beeen calibrating the thermometers, initially I just believed them. Since then I have calibrated them. I have two and both overread at boiling by 3 and 5 degs, so some of my previous mashes have been a bit too cool. I have thought about making a "boat" to float on the mash with the thermo dangling but in the end decided it was a bit too OTT and possibility of breakage to the glass.

Thanks for the reply, its looking like digi is the way to go.
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Post #4 made 9 years ago
by Lumpy5oh
Definitely check out the thermoworks site. You can never have too many thermometers. You want to be stirring constantly turning the mash bed over while heating. There can be layers at different temps throughout the mash so stirring helps to keep everything constant. I use a 10 inch propane burner and my kettle has a pretty thick bottom. I have to shut the gas off a few degrees below my target to allow all the heat to be transferred thru the thick bottom. I also stir during this time as well.
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Post #5 made 9 years ago
by mally
Jomay - Dont fall into the trap of presuming that any digi thermometer will solve your problems.

Have a read of This.

I have a lot of faith in the Thermoworks products (specifically the Thermapen). I do not think it is a perfect device though, plus it is expensive.
Probably the best thing to do is check against many others, especially if you know of other grain brewers. Or look at the ads at the bottom of this site, others recommend the Comark model which is a lot cheaper.

Edit ### - I have just noticed the ads have gone, so ignore that! :scratch:
Last edited by mally on 26 May 2016, 19:38, edited 1 time in total.
G B
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Post #6 made 9 years ago
by meryvn
Yeah I don't fully trust my thermometers which was why I had two. I had checked them both at boiling and freezing temperatures and both read within a degree of what they should, which is no guarantee that they will read correct at mash temperature but is the best I can do at home.

For a bit more money the maverick thermometers seem well regarded in the bbq scene but I thought it was overkill for my needs.

Sent from my XT1092 using Tapatalk

Post #7 made 9 years ago
by joshua
If you want to Go Purely Scientific, The Boiling point of Methanol is 148.5F/67.7C.

A product used to help start Cars is Called "HEET" and is 100% Methanol.

If you can get a "hot plate" OUTSIDE, and slowly heat the Methanol in a heat safe container, while checking your Thermometer(s), you can find a thermometer that is Very Close to MASH Temperatures.

Methanol is Very Flammable, so, be Careful.
Honest Officer, I swear to Drunk, I am Not God.
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Post #8 made 9 years ago
by PistolPatch
Jomay, I can't find a pic atm but will look tomorrow or take a pic and post it of how to 'float' a probe on your wort, if you have a thermometer with a probe.

You are right to not trust any single thermometer and mally has posted you a good link. When probes get dodgy, boiling them in water will usually 'free' them up again.

Where is that damn pic???? :)
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Post #10 made 9 years ago
by PistolPatch
Thank you Josh :salute:. The first one is the one I was trying to find ;).

Also Joomay, in mally's link above, you'll see two white thermometers that have probes. They are really cheap and, surprisingly, are also amongst my most accurate thermometers so maybe get one or two of them?

I say two, as when using a probe thermometer, with that type of probe, you always need to have a double-check. It's happened to me twice where the probe has got 'sticky' - once just a few weeks ago... One of my white thermometers started reading 10C above the other :argh:. Anyway, I caught it because I do a double-check.

Boiled the dodgy probe in water as mentioned above and it is now working perfectly again.

Next century, I'm sure we'll have none of these problems :P.
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Post #11 made 9 years ago
by Jomay
Thanks very much for the replies.

More to this than I was thinking. Probably I am a bit too impatient, I was hoping for "what you need is one of these" :-) A bit of reading and searching to do. I dont need anything too exotic as I only have a basic setup so an expensive advanced gismo would be wasted. Still, getting a bit closer with the temperatures than I have been doing would be a good thing, and most important a quicker readout.

Joshua, at first look I dont see any HEET for sale in the UK. Maybe there is an equivalent, or perhaps I can buy methanol directly(model aeroplanes used to run on it I seem to remember). Pity Acetone hasnt got a higher bp as I have a gallon or so of that :-)

I liked that first photo of the boat but its not clear why it doesnt sink, there is no mention of a seal around the hole. Am thinking maybe a rod across the boiler with the sensor dangling from it, I suppose it comes down to shape and size of the sensor.

Once again thanks very much to you all, best wishes.
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Post #12 made 9 years ago
by meryvn
I would steer clear of the boiling methanol idea, very flammable liquids that high above their flash point is a recipe for trouble. If you are getting 0 and 100 readings accurately then you want be too far out at mash temperature. Having more than one thermometer can help ease the mind as well.

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Post #15 made 9 years ago
by ShorePoints
On Joshua' posts above concerning thermometer calibration using methanol or acetone, I would say definitely do not try this at home using acetone. If you must, you had best plan for what to do when it catches fire. For methanol, look it up to see 64.7 degrees C (148.5 deg F) = boiling point. Still dangerous vapors involved - doing it outdoors as suggested is far better, but you can also take advantage of there being no methanol / water azeotrope. Mix 1 Part MeOH to 3 parts water, heat outdoors with lots of ventilation, watching your thermometer as you go past 60 degrees - the rate of increase will slow and the methanol will boil off independently from water before the temp rises again and you can call it at that point. This will not work for most other water miscible (mixes totally) solvents you can get - they boil together on a curve, not separately.
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Post #16 made 9 years ago
by aamcle
Or buy one quality glass (old fashioned) thermometer and use it to check others.

It's easy to go pt100 and cheap, £4 or so for a pid and £17 for thermometer/display part.


Aamcle
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Post #18 made 9 years ago
by Wadey82
I'm using a thermowell with a digital thermometer, I've checked this against an a standard thermometer and there is about 2 deg difference. Which one is correct I have no idea. The thermowell is handy as I have a constant temp reading, however I have to regularly agitate my mash to ensure I don't have temp differences in my kettle and there can be quite a difference. But I don't mind giving my mash a stir every 10 min, makes me feel that I'm helping my beer come along.
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Measuring Mash Temps

Post #20 made 9 years ago
by Contrarian
I knew a plumber who worked at a hospital and one of his jobs was to ensure that water coming out of taps was at the correct temperature. For obvious reasons it's fairly important to get that right!

He had an awesome thermometer that I was admiring one day. It was digital with a probe but it was worth about $400 and he sent it away to have it calibrated at 40C twice a year at a decent cost.

I guess my point is that precision measurement that is reliable is expensive but for the average home brewer a margin of 2C is manageable but anything more could be a disaster.

I still use a spirit stick thermometer but normally I just aim to get my strike temp on the money and leave it at that.

I'm not trying to minimize the importance of mash temp. Most people will be able to taste the difference between a beer mashed at 69C and one mashed at 63C but I'd be surprised if many people could taste the difference between a beer mashed at 65C and one mashed at 67C.

I'm rambling a bit but having an old faithful or two that you can trust and calibrating other thermometers against them will get you near enough to where you want to be.

As a mate said to me when I was starting out "if your mash temp is somewhere between 60 and 70 degrees you'll make beer"!
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