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Mash temperature readings all over the place (for PM)

Hi all,

I did my first partial mash over the weekend. Everything went pretty smooth, except I had an interesting experience regarding mash temp & thermometers. I brought my water to the strike temp, doughed in and then stirred for a couple minutes before reading the mash temp. The readings with my digital thermometer bounced all over the place (literally jumping 10* - 20*) depending on where I put it in the mash. It confused the hell out of me because I would see it read my desired mash temp of 154* in some spots, and then a slight movement of the thermometer would suddenly result in 162*, 144*, 138*, 156*, etc. It was not stable at all. So I put the lid on the kettle and went to the basement to get my old school glass lab thermometer. Couple minutes later I dropped in the glass thermometer and the mercury (eventually) stabilized around my desired temp (I admit, I’m not the greatest at reading exactly where the mercury is on those).

My question is… anyone else had this same experience? Is a digital meat thermometer not ideal for reading a mash? Or did I perhaps not stir enough?

All thoughts and ideas are welcome. Just looking for something to try on my next PM.


Sounds like you didn’t stir the mash up enough to distribute the heat evenly. Like you later found out, it most likely stabilized around where you wanted it to anyway.

Also, your strike water may not have been uniformly heated. With my stove the water over the fire is a good 6-8 degrees warmer than the sides of the pot. I counteract this by slowly stirring the water.

Interesting. Thanks for the info. I’ll slowly stir the water when its heating up next time to get it to heat evenly. Also, how long do you typically stir the mash before recording the temp? I felt like I stirred for a good 1-2 minutes at least, but who really knows. I didn’t time it or anything.

what kind of thermometer do you have?

There isn’t an exact time you have to stir when doughing in. Every beer is different. Just stir until there are no more dough balls and take a temp reading in a few different places. If they aren’t very close then stir some more and take another round of temperature readings.

Good question. I’m not sure who makes them, and I’m not at home to check. But I have an old school glass thermometer that came with my NB Deluxe Starter Kit, and the digital thermometer is my wife’s meat thermometer from the kitchen. I’m planning to stop at my LHBS this week and pick up whatever they recommend. I’m looking for one that’ll clamp to the side of my kettle because I’m tired of having to hold my thermometer in there until I reach desired temps.

Ah, okay. Thanks for the info. I’ll do that next time. If my temp readings vary in different spots, I’ll stir more and try again until they’re consistent.

I have one more question about mashing. When your temp readings stabilize and are a little on the low side, what is your method for raising the temp? I’ve heard of some people having extra water heated up on the side and adding that to the mash to raise temp, if necessary. But why not just apply low heat and stir? Wouldn’t constant stirring prevent scorching the grains? It just sounds easier to me than having to heat up extra water…


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