So how do you measure your mash temp?

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IowaStateFan

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This may seem like a silly question, but I'm just curious how everyone measures their mash temps. When I started all-grain, I used an analog instant read thermometer, but kept getting inconsistent readings. I then bought a digital probe thermometer at Wally World that has a silicon sheath over the cable. I've checked it in ice water and boiling water and it seems to be accurate.

Yesterday, I stirred the heck out of my mash, threw the probe into the center of the mash and got a reading of 144. My strike temp was supposed to be 152. I stirred some more and the temp started to rise. I closed the lid and watched the temp rise over the next 5 minutes to 150.4 and said, "good enough". Over the next 20 minutes or so it dropped to 148.8 and held there for the rest of the hour. I stirred the mash to check for conversion and the temp quickly rose to 153.

This is typical for me, and all I can say about my mash temps is that they've been somewhere in the conversion range and that I've made beer. Since mash temp is key to getting the type of fermentables you desire, how can I determine what my mash temp is with any precision? Needless to say this is somewhat frustrating.
 
I have a submersible temperature probe that stays in the mash during the entire process. I move it around and average several readings when I want to know exactly how the mash is doing.
 
i think ome of the programs has a strike temp calculator. based on the #grain and the needed mash temp it calculates the strike temp water that will needed to be added.
 
what type of mash tun are you using? i use coolers and this is typical for coolers, but there are a few things you can do to help. are you pre-heating your mash tun with hot water? the insulation in a cooler can absorb quite a bit of heat. i typically fill my mash tun with near boiling water and let it cool to my strike water temp with the lid on. my strike water temp is usually around 170F. i use the calculator in beersmith to figure this out. you can also define a handful of variables in the program like how much it weights and what it's made of. this helps the program better gauge what temp you need. the other thing to consider is when you pour 70F grain into 170F water there is going to be a lot of temp variability for a while. i add 2 degrees to my calculated strike water temp and stir the mash until i settle into that temp. you're going to have to stir the mash anyway, and stirring the mash will cause heat loss. after my mash has settled in i can come back in 20 minutes and the middle of the mash is still at my desired mash temp, but the mash along the wall of the cooler could be 3F-4F lower. you can't really do too much about this besides further insulating your tun. i haven't decided whether it's better to stir, which will lower the temp everywhere, or to leave it so at least the core of your mash is at your desired temp. i think the most important thing to think about regarding mash temps (like most things in brewing) is to find a system that works and stick to it; be consistent. as long as you have a system that gets you to a starting mash temp you want, and then you do the same things to maintain that mash temp (or not) every time then you'll have the ability to make a consistent beer.
 
I too have had issues with this. I have been using a instant-read digital thermometer. near the end of the mash, I took a couple of readings, and it was reading low(around 146). Since the hour was pretty much up, we decided to go ahead and lauter. I took a reading of some of the first runnings and was suprised to see the temp at 152. What is up with that? I guess that I need a thermometer that will go deeper or something.
 
I know it's hard to get an exact reading. I've found that it really helps NOT to measure the temp until you've fully stirred well and let the grain pull in the heat from the strike water. If you're in a pocket of water, it will read high and if it's touching grain, it will read low. Close the lid for 5 minutes, let things stabilize, then go measure the temp. I like to lightly stir the mash with my instant read digital so that I'm getting more of an average rather than a pinpoint.
 
This is a good question. Thanks IowaStateFan, I wondered about this myself. I always go by the reading in the middle with my digital probe thermometer. The sides are a little lower.

I shot for a high temp of 158 degrees with beersmith and it worked well on both of my PMs so far. I was right on on the first PM and at 157 on the second one. So according to my setup and beersmith, the middle seems to be the temp to take.

I guess your mash can't all be one temp. It'd be nice to know the exact layout of the temps in the mash. for instance...

15% at 157
30% at 156
35% at 155
20% at 154

I'd bet more mash is at the outside (lower) temps than the inside (higher) temps cause the outer area is larger. Just take the temps in the same places and make them work for you.
 
Have you ever been swimming in a lake in the summer, and all of a sudden you swim past a nice warm spot? But then 5 feet later you hit a freezing cold spot? The point I'm making is that even pure liquids can develop hot/cold spots. It makes sense that a mixture (mash) with such high viscosity would behave the same way. I'm guessing if a speed boat zoomed through those hot spots, the lake would have a more consistent temperature in that area.

Try giving your mash a good stir. I watched AG video series (see the sticky threads in this forum) where (Yuri?) had a paint stir on the end of a drill - I'd imagine this does a pretty good job of distributing the heat in the mash tun.

I'd also imagine that even the digital thermometers aren't perfectly accurate... maybe something like +/- 2 degrees - so a 4-5 degree fluctuation might be right in line with the tolerance of the thermometer.

So my two cents: So stir it up well, and take the average of a few measurements.
 
I have a probe through a thermothingy into a keggle, but found this to be too unreliable. Now, I just use it as a guide and use a calibrated Taylor bi-metallic analog probe thermometer at a few different locations in the mash. I calibrate it nearly every brew, but usually find it dead on. I just don't like the fact that the digitals (all the ones I've seen) aren't calibratable.
 
First, get an accurate waterproof thermometer. This one is popular for brewers. it's NIST traceable and it's waterproof. I have 2. They work great. But just be warned, it constantly updates and is very sensitive, so you need to stir plenty while taking measurements. I routinely will leave it in the mash and it reads 153, and when I come back a few mins later, it reads 180. Stir it up, and it's reading 153 again.
 
I had the same problem and thought it was my thermometer. So I got me a dial one that is used for compost (80-195F range) and then I also got several alcohol thermometers.

The thing I found out is ever one is a little bit off. So I stopped worrying about the difference but have adjusted the compost one to read what I consider accurate at 150 (Several of the alcohol ones in water then calibrate).

When I mash I put the thermometer in the center and leave it there (small hole drilled in top of lid) I have noticed that it stays pretty constant.

This works for me. It is repeatable (have a mark so I know how deep to slide it through the lid), and I can measure from batch to batch. It is repeatable, maybe not 100% accurate, but repeatable.

Think about it this way. You want accurate, and I do mean accurate mash temps, you either need to find a way to constantly stir it, and take temps from different levels, or figure out a way to measure numerous levels at numerous points in your tun.

The thing is you have to figure out what you are comfortable with and make sure you can repeat it.
 
Thanks everyone for the responses. Based on the responses it seems that because there are hot and cold spots in the mash you need to either take multiple readings from various parts of the mash and average them, or to stir constantly. Neither seems all that practical. I'm afraid of losing too much heat by keeping the cooler open to check the temps. I pretty sure that I'm pretty close on the temps, though my anal-retentive side wants to be precise, especially considering that small changes in temp can have a large change in the finished product.
 
Have faith that the cooler will hold temp. You don't have to keep opening it up. I only measure 5 minutes after doughing in and then again at the end. I lose 2-3F over 60 minutes.
 
I have a permanent temperature sensor in my site glass for a reading down by the burner and then I use a pocket digital thermometer to take the temp from the top also.
 
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