Thermapen mash readings

[pj_rage]

So I had a thermapen before I decided to take up brewing. As you all know, it's an awesome thermometer which gives quick and accurate readings.

Naturally it is my go to for mash temperature readings, but I've been having a lot of trouble using it for this, so I wanted to get some other takes on using it this way.

First off, I do BIAB all grain, so I'm mashing in an 8 gallon pot, usually thich at around 1.25qt/lb. Taking readings with the thermapen of the strike water is quick, stable, and (seems) accurate.

My problem is with trying to figure out what the mash temp actually is. The probe is only 4.5" long, which gets me ~40% or so deep into the mash. Depending on where and when I measure, I get wildly differing results, and when mash temperature differences of 2 degrees (F) or so make a difference, it's frustrating. If I measure the dead center, I'll get one reading. If I measure it a few minutes later, it's a different measurement, off by as much as 5-6 degrees. Stir, and it's different again. Let it sit and it's different yet again. If I measure at the same depth but in different places, not the center, the difference can be as much as 8-9 degrees different. Also, whereas the temp is usually very stable with the thermapen (taking any other kind of reading), the temp takes a while to settle, usually slowly counting upward before settling.

I'm not really sure what to make of it, but eventually I get enough low readings that I start to freak out and add heat.

Just to go over a rough example quickly..

-Heat the strike water to the calculated temperature based on software.
-Add the grain, stir, put the cover on, wait ~5 minutes
-Take a reading in the center. It's normally within 1 or 2 degrees of my target temp, say 154. I then take readings in different places, and notice that one spot will be 152, another 156. No big deal, I'm happy with my 154 average and leave it.
-Check in 30 min (half way done). Might read 151 in the center. Not sure if the insualted pot with 4.5gal would have lost that much that fast, I stir and take another reading. Reads 148 in some places, others 153.5 What's the real temp here?
-I wind up getting different readings every time I stir, and different again after I let it sit. If I end up adding heat, it will seem to not change for a while, then suddenly I'm reading 158-159 in some places and 151 in others. So it becomes hard to know when to stop the heat (or if I should have added it at all).

My real question I guess is where exactly should I probe it, and how can I know what the "official mash temp" even is? I know you will probably say let it sit, and I do, but for how long? I let it go 5 minutes usually and it will still read different temps at different places, none of which are what I want to see (usually low). But if I stir (without heat or cooling), let it sit another 5 minutes, I'll get a different reading off by a couple to a few degrees from the last. I don't know which to believe.

Sometimes I think instant temperature readings are a blessing, but more of a curse for mash temp like this. I do toss in my floating thermometer, and it holds a lot more stable temperature, but I don't trust the numbers on it, so it's about useless.

So, sorry for the long post, but what do you guys all do with your thermapens? Do you notice similar results? At what point do you "know" you are at your mash temp? Do you just take the one initial reading after a few minute rest and call it good to go? What really gets me is that if it's just water (strike water for example), I can stir and stir and do whatever and the reading just holds nicely within a degree or two. But with mashing, it seems that there are different pockets of wildy varying temperatures all over the mash, and I don't know which to believe.

 

[SpanishCastleAle]

I use a digital meat thermometer so it's not as accurate or fast as your Thermapen. When you dough-in how long do you stir? At dough-in, it takes me quite a bit of stirring to get a uniform temp throughout the mash. That's actually how I know to quit stirring...consistent/uniform temp readings. Then after it's consistent I leave the probe in the mash and after a few seconds it's pretty stable.

So I guess my only suggestions are:
1) At dough-in keep stirring until the mash is uniform temp. It helps to have a big mash paddle.
2) When the mash is uniform temp, insert Thermapen and let it stabilize a few seconds, then read/record the temp. Be consistent in how/when you read/record the temp.
3) If your pot is not insulated maybe try to insulate it. I use a ginormous beach towel, folded over lengthwise in 3 layers, wrapped around the pot and held in place by one of those ginormous rubber bands you can get from Home Depot.

 

[Hoppocrates]

I agree, proly gotta stir it up to get accurate reading...

 

[pj_rage]

I'll try to stir more thoroughly. I've never timed it, but I'd say I stir for at least 2 minutes after dough in. Basically until any little dough balls are gone, and it's got a uniform consistency.

The funny thing is that stirring it is what seems to make the readings less stable. Right after stirring is when I'm seeing the biggest fluctuations not only between different locations at the same depth, but even in the same location a few minutes apart. Normally I wouldn't care about a couple degrees difference, but when you are trying to hit 154 and not 152, it's hard to tell when to add heat and when to accept which reading.

 

[SpanishCastleAle]

2 minutes isn't enough, that's just the bare minimum to get it mixed up, keep stirring until the mash temp is uniform. Try 4-5 minutes and measure it, then you may have to go a couple more minutes. When you stir, try to stir up grain from the bottom up to the top. If the mash is loose enough you should be able to get a churning motion going (without introducing much air) so the whole mash is sort of turning over in the pot.

When I first got my mash paddle from Mashpaddle.com I thought it was way too big, it's like 4' long and I only make 5 gal batches. I was wrong, that mash paddle is the perfect size for 5 gal batches.

 

[Catt22]

IMO, it's near impossible to achieve a perfectly uniform grain bed temperature when doing a simple infusion mash. Insulating the tun would certainly be beneficial as would using a cooler for the MT. IME, after the dough in and thorough stirring, it can take upwards of another 10 minutes or so for the mash to stabilize and even then, the temperature won't likely be very uniform. The best you can hope for when infusion mashing it to achieve an average grain bed temperature as close to your target temp as possible. Extensive stirring does help, but at the same time you are losing a lot of heat with the top of the MT opened. When using a Thermapen with it's relatively short probe, I would just insert it as deep as possible into the grain bed about half way from the center to the side. This position would probably give you a decent representation of the average grain bed temperature.

This sort of dilemma with the Therampen and other similar digital thermometers with very short probes is what led me to using a thermowell in the MT with a digital thermocouple thermometer with a long "k" type wire probe. I also made the switch from simple infusion mashing to a RIMS system primarily for it's ability to maintain more uniform mash temperatures. Before the RIMS, it was a highly hit or miss situation. Changing batch sizes and brewing in a fairly wide range of ambient conditions made it even more challenging. I do remember that larger batch sizes seemed to be much more stable temperature wise. Just my take on this. YMMV as always.

 

[pj_rage]

Catt, would you mind offering some more details on your exact thermowell/thermocouple/probe setup?

I'll also have to look into RIMS, I've not heard of that yet (but I'm still new!).

I did think about excessive stirring causing heat loss itself. Just like stirring soup cools it off, I wouldn't be surprised if the act of stirring for 5 minutes would itself cause at least a 1 to 2 degree drop. I guess I'll just have to factor this into the strike water temp.

 

[Catt22]

Sure, here ya go:

The DIY thermowell is simply a section of 1/2" copper pipe capped at the bottom end. The orange rod you see sticking out of it is a piece of a fiberglass driveway marker that I use to hold the probe in place at the bottom of the thermowell so it remains in contact with the copper cap at the bottom for a fast response. The digital thermometer is this one from Cole-Parmer and it reads continuously with a resolution of 0.1 degree. I like that feature when operating the RIMS as you can see even minor temperature changes and know which way it's heading when heating the mash or not:

http://www.coleparmer.com/catalog/product_view.asp?sku=9121045

Both the thermowell and the sparge/wort return manifold can be easily adjusted vertically for various batch sizes.

 

[pj_rage]

Awesome, thanks for sharing. That setup looks pretty straightforward, and the cost of the thermometer/probe isn't too bad. I'm definitely going to keep that in mind.

 

[pj_rage]

Catt, have you found that cole parmer model to be very accurate and consistent for measuring temperature? I'm between that one and the MTC from thermoworks with the model #113-372-T probe. I wouldn't mind saving some money with the cole parmer, but more than anything, I want the greatest accuracy and consistency. One thing about the cole parmer is that the probe itself is only 5" long, and the plastic and wiring says it can go to 90C. Good enough for mash temp full submerge, but not for boiling submerge. Not sure I would ever want to do that anyway, though. I'm curious if submerging the nylon 6/6 in the hot wort is "food safe" though? From what I can find, it looks like nylon 6/6 is food safe, but I'm not 100% certain.

 

[Catt22]

Catt, have you found that cole parmer model to be very accurate and consistent for measuring temperature? I'm between that one and the MTC from thermoworks with the model #113-372-T probe. I wouldn't mind saving some money with the cole parmer, but more than anything, I want the greatest accuracy and consistency. One thing about the cole parmer is that the probe itself is only 5" long, and the plastic and wiring says it can go to 90C. Good enough for mash temp full submerge, but not for boiling submerge. Not sure I would ever want to do that anyway, though. I'm curious if submerging the nylon 6/6 in the hot wort is "food safe" though? From what I can find, it looks like nylon 6/6 is food safe, but I'm not 100% certain.

The Cole-Parmer unit is a traceable model, meaning that it has bee lab calibrated. I've found it to be very accurate. You can also calibrate it yourself if desired, but then you would void the traceable calibration. I replaced the OEM probe with a longer plain wire type "K" probe. The probes are quite inexpensive. I would not submerge any probe beyond the metal tip section. It's best to either buy a thermocouple with a very long metal tipped probe or use a thermowell. I went the cheaper route with the thermowell. Thermoworks sells some good equipment, but I think they are generally overpriced on most stuff.

 

[SpanishCastleAle]

From what I can tell (Catt22 can confirm/deny), the nylon rod doesn't contact the wort, it just puts some weight on the thermocouple junction such that it is in contact with the copper thermowell, so it's more accurate and faster.

Nice setup Catt22.

 

[pj_rage]

Ah ok, so when you used the standard probe with it, you just put it in 5"? In that case, I wouldn't be much better off over the thermapen, except that I could keep it in the mash the entire time.

Excuse my ignorance, but what is the bottom of the thermowell -- that is, how does the thermal transfer to the probe happen? Is the plain wire probe you have down there just stuffed down there and floating in the airspace of the copper thermowell, relying on the copper getting hot via conduction with the mash, then relying on convection in the air gap between the copper tube and probe to take the reading? Or is there some medium the probe is in to get conduction from thermowell to probe? Or is the probe mounted directly to the inside of the copper tube somehow?

EDIT: Just saw SpanishCastleAle's respone... that would answer my question, if the nylon rod is basically pressing the probe against the thermowell. How fast does the thermowell/probe respond to temp changes with this setup?

 

[Catt22]

Ah ok, so when you used the standard probe with it, you just put it in 5"? In that case, I wouldn't be much better off over the thermapen, except that I could keep it in the mash the entire time.

Excuse my ignorance, but what is the bottom of the thermowell -- that is, how does the thermal transfer to the probe happen? Is the plain wire probe you have down there just stuffed down there and floating in the airspace of the copper thermowell, relying on the copper getting hot via conduction with the mash, then relying on convection in the air gap between the copper tube and probe to take the reading? Or is there some medium the probe is in to get conduction from thermowell to probe? Or is the probe mounted directly to the inside of the copper tube somehow?

The pipe is capped at the bottom. It's all copper and has excellent thermal conductivity. The thermocouple I am currently using is the plain wire type "K" with a bare junction (ie no SS tip). The junction of the thermocouple is in direct contact with the copper. IMO, there's no need to get all mind snargled about the air gap/convection/conduction/airspace stuff. Think about it. The thermowell is submerged deep in the mash and being made of copper, it warms up very fast and so does the air inside at the very bottom. There's a lot of heat conduction and heat radiating inside that pipe and it happens pretty quick. I just shove the wire probe down the pipe and hold it in place with the ram rod. It's nothing super high tech, but it's a cheap way to do it and it works. The response time is excellent as far as I can tell empirically.

 

[Catt22]

From what I can tell (Catt22 can confirm/deny), the nylon rod doesn't contact the wort, it just puts some weight on the thermocouple junction such that it is in contact with the copper thermowell, so it's more accurate and faster.

Nice setup Catt22.

That's basically correct, but not exactly. I've changed thermocouples since that pic and now use the plain wire exposed junction cheap one. I did not like the springy coiled OEM probe. Well, not so much that I did not like it as much as the plain wire type better fit my application. The replacement thermocouples are dirt cheap. I think I bought five of them for about $15 including shipping. I used some 1/4" OD icemaker water supply tubing to make a short of a sheath for the wire leads. The idea was to make the plain wire leads somewhat more rigid. The bare junction protrudes from the end of the tubing at the bottom. Then, the fiberglass is used to wedge the wire (and the cover) against the side of the pipe to hold it in place. You could use anything for this. A wooden dowel or even a pencil would work as well. It does not contact the grain so it doesn't much matter what you use.

 

[rico567]

I use a Thermapen for all brewing ops, and love it. My mash is done in a 10 gal. Rubbermaid conversion. My belief* is that problems measuring mash temps result from inadequate mixing of grain with strike water- pure and simple.

*My belief, however, is not just theoretical. When I started brewing AG, I was getting low Brix on my refractometer. When I started stirring twice as long, suddenly the numbers fell into place. I conclude that temperatures can be made uniform -or uniform enough- in a mash, but the way to get that is to stir, stir, stir.

 

[Catt22]

I use a Thermapen for all brewing ops, and love it. My mash is done in a 10 gal. Rubbermaid conversion. My belief* is that problems measuring mash temps result from inadequate mixing of grain with strike water- pure and simple.

*My belief, however, is not just theoretical. When I started brewing AG, I was getting low Brix on my refractometer. When I started stirring twice as long, suddenly the numbers fell into place. I conclude that temperatures can be made uniform -or uniform enough- in a mash, but the way to get that is to stir, stir, stir.

I generally agree on the advantage of stirring a lot. My efficiency has never been terribly good and typically would run about 75%. My procedure was to dough in normally, stir well then pretty much otherwise leave the grain bed undisturbed while circulating and doing the steps. This time around I stopped pumping and stirred the mash very well after each step was finished. I also did this at the end of the mash out just before beginning the sparge. So, I stopped and stirred four times during the mash. My efficiency went through the roof. The only thing I did differently was the multiple stop and stirring. I used this method again just a few days ago and the results were the same. I am now a firm believer in stirring and stirring a lot. Previously, I was of the opinion that it was best to disturb the grain bed as little as possible. I'm guessing that I had a lot more channeling going on than I realized. The added benefit of stirring is improved heat distribution throughout the grain bed. It's a double win IMO.

 

[pj_rage]

Even with the problems measuring temp, I got mid 80% efficiencies on my last two mashes. I did feel like I was stirring enough, but I'll stir even more to see if I get more uniform temps.

Rico, when you say you get uniform readings with the thermapen, how much fluctuation in temp among different depths, locations, and times do you consider to be uniform?

 

[Catt22]

Even with the problems measuring temp, I got mid 80% efficiencies on my last two mashes. I did feel like I was stirring enough, but I'll stir even more to see if I get more uniform temps.

Rico, when you say you get uniform readings with the thermapen, how much fluctuation in temp among different depths, locations, and times do you consider to be uniform?

Mid eighties is very good IMO. Excellent actually. No need to chase it further IMO.

I'm wondering the same thing about using the Thermapen. I just can't see thrusting my hand, arm and the thermapen deep into a hot grain bed sometimes containing as much as 34 lbs of malt. Ouch!

 

[rico567]

Even with the problems measuring temp, I got mid 80% efficiencies on my last two mashes. I did feel like I was stirring enough, but I'll stir even more to see if I get more uniform temps.

Rico, when you say you get uniform readings with the thermapen, how much fluctuation in temp among different depths, locations, and times do you consider to be uniform?

I have no experience with doing any sort of variations in taking temperatures that you describe; what I was posting was the purely empirical results I have obtained by stirring more. My only temperature readings were obtained by sticking the Thermapen in the mash about 3".

When I began to brew AG, I evolved a pretty good idea by trial & error (not much luck with brewing software) that X temperature of strike water on Y pounds of grain in my MLT preheated with Z temperature of water will produce the correct mash temperature.

My initial error lay in just stirring until I had what appeared to be the correct mash temperature, closing up the MLT, and walking away for 60 or 90 min., as required by recipe. But I was getting low readings, maybe 2-3 Brix. After reading a few HBT threads, I began to doubt I was stirring enough. When I extended my stirring from a few minutes to a few more minutes, I began to hit the correct OG for that recipe.

Disclaimer: It would appear from reading several posts in this thread that the brewing methods of the posters are quite different. For the record, my brewing philosophy is strictly KISS, and if I can find a way to simplify something else, I do it. My practical experience of techniques are therefore very limited, to just my own methods....but within that narrow framework, I know what works.
Mashing, which is what is being discussed here, I do with a 10 gal. Rubbermaid "Big Orange" MLT conversion with the Bargain fittings kit. Strictly a single batch sparge of about 3-4 gallons following an initial 5 gallons of strike water. Therefore I don't use, am not familiar with (although of course I understand the theory) of continuously heated / circulated systems, thermowells, etc.

 

[pj_rage]

Just to clarify, I'm not trying to improve my efficiency by stirring or monitoring the temp or anything. I've been very happy with my efficiency!

My real problem here is that I want to be able to mash at particular temperatures, and one step in doing this is actually being able to measure the mash temp at any given time. When I use the thermapen, even after stirring what I thought was a good amount, I wind up with different readings from different areas and depths of the mash, and even in the same area/depth taking the readings a few minutes apart. I basically don't know which numbers to believe, and it also causes trouble with consistency and repeatability.

My takeaways from this thread so far, are to stir even more (~5 minutes stirring) to try to get a more uniform temperature, standardize my readings to be one quarter of the diameter of the mash pot in from the edge, at the maximum depth of the thermapen (4.5"), and try to insulate my pot even further. I'm going to try these steps and see if it helps. Also, if I get the urge to spend some more money, I might get the thermoworks MTC or cole parmer, with thermowell and probe, so I can constantly monitor the temp and get a better idea of how it is changing over time.

Rico... when you take your measurements at about 3" deep, they do seem pretty consistent? Say, within a degree each time you poke it to check (in a few minute span)? Do you always poke the same exact spot, or do you poke any old place at 3" deep? If you do different spots, is the whole mash within a degree or so at 3" deep at any given time? Sometimes I can get a very stable reading, within a half degree at the same depth over a very wide area of measurement. But then I stir for 30 seconds, check again at the same depth, and not only is it not within that same half a degree region, but it's varying by several degrees at the same depth, depending on where I measure. This makes me wonder which measurement was right, the first one, the average of all the new ones, or what?

Another problem I'm thinking of... say I want to hit 154F for the mash. If I dough-in, stir for 5 minutes and wind up getting a relatively uniform measurement of 152F, I'll want to add heat. This is going to then be a guessing game of how long to leave the heat on for, then only the bottom of the mash will be hot and I'll have to stir for another few minutes to get it uniform again, and hope that I left the heat on long enough (and not too long!). I guess this will get easier with time and experience, but when it seems like (from what I read) a few degree difference in mash temperature can make a big difference in your final beer, it's annoying not to be able to hit the desired temp. This would almost be easier if I just had a pot-mounted thermometer, or just used the floating thermometer.. then I would never be the wiser that anything was wrong with mas temp, lol. It's the curse of the speed and accuracy of thermocouples like the thermapen, I guess.

Anyway, I'll report back here with some detailed notes and results next time I mash, but unfortunately, I think it's going to be after the new year.

 

[Catt22]

pj,

You are far from alone on this. Direct firing a MT tun can be very tricky and also very hit or miss. The problem is that even with experience, it's a moving target. Everything changes when you go to a different batch size, different water to grain ration or brew in different ambient conditions (ie hotter or colder/windy or not etc). It's very difficult to judge how much heat to apply and for how long mostly because of how much time it requires for everything to equalize. There's considerable lag involved. Also, you can't effectively stir the wort below a false bottom, so it will tend to overheat and the heat will only very slowly diffuse through the mash.

IMO, precision mash temperature control is one of most challenging things to get a handle on and I agree that you only need be off a few degrees to affect the finished beer. The effective mash temperature range is fairly narrow at about 149-158F give or take. I'm also convinced that many times when beer finishes out with a high FG it is a result of the mash temps being too high. I also think that often the mash average temperatures are much different than what the home brewer believes them to be.

 

[SpanishCastleAle]

FWIW pj,
When I use the meat thermometer I leave the probe in the mash the entire time (~3" deep). It will actually display a MORE stable reading than the mash itself. What I mean by that is, say I reach a stable rest temp of 154* F and let it rest for 10-15 minutes. The digital thermo display stays at 154* F but if I then stir the mash it will drop to 153* F or so.

I direct-fire (with a false-bottom) almost every brew but I keep the heat VERY low and try to stir it frequently with that churning motion I mentioned earlier (the whole mash rolling over in the kettle). I also sometimes pull some wort from the ball valve and return it to the top of the mash (which pulls new wort from above the false-bottom to below it). Also, in an effort to reduce the amount of direct-firing and to help keep the mash temp constant I always have a quart or two of simmering (almost boiling) water and add it in as needed to maintain temp.

Also, I have a kettle-mounted thermometer but never use it when mashing. I could never get it to agree with the meat thermometer, seems like it being in contact with the kettle itself affects it's readings. That's one of the things I like about Catt22s setup; the copper thermowell is only contacting wood (poor conductor, good insulator).

 

[pj_rage]

Yeah I almost need to get a non-instant read thermometer so it just sits relatively stable and I can use whatever number it says. The problem with the thermapen is being able to identify even the smallest non-uniformity in temperature and then it gets me to wondering. I think even a copper thermowell would help.. something to heat up and maintain some heat to give a little stability and smooth out the readings to some reasonable average.

I really like the idea of boiling/simmering water on the side to add instead of direct firing though. That seems like it would mix in better and give a more stable temp more quickly than direct firing.