Mash temp rising during mash?

[blanchmd]

So my last two batches I have experienced my mash temp actually rising during the mash. I have a rectangular cooler system. Anyone have this happen? It is discouraging to hit the mash temp on the nose and then come back an hour later to see another 4 degrees there. Maybe I need to just monitor the temp frequently throughout the mash? Thanks

 

[schematix]

Probably temperature stratification or a non-homogeneous mixing. Where are you measuring? Are you stirring?

 

[TheMadKing]

It sounds like you need to stir better when you mash in. It's impossible to actually gain heat without a heat source, so you are likely just seeing pockets of strike temp water that weren't properly mixed. I usually stir my mash vigorously for 2-3 minutes at dough in, then every 20 minutes during the mash (and check temps at each stir)

Hope that helps!

 

[Stillraining]

Cool Perpetual motion beer.. gimie, gimie..

 

[blanchmd]

I stir pretty well, I thought, but perhaps not well enough. I am definitely going to be paying more attention to the mash. Thanks

 

[RM-MN]

I think that the starch to sugar conversion may be slightly exothermic so a small temperature rise in the middle of the mash may happen. If you stir you'll mix that warmer part of the mash with the cooler mash next to the edge of the tun where it has lost some heat and hit your mash temp perfectly.

 

[MagicMatt]

I find the temp doesn't stabilize until 15-20 minutes into the mash. It will slowly rise until it plateaus.

If you've "hit your mash temp on the nose" within a couple of minutes of dough-in, then you've likely actually overshot it as it hasn't had time to stabilize yet. If my mash temp is targeted as 154°F, then my strike water will be 163°F. Right after dough in, my temps are around 145°F, and slowly climb to 154°F over the next 15 minutes or so.

 

[The_Bishop]

If those are your results, you need to stir more during your dough-in. Any case of temperatures rising during the mash without adding heat is evidence of temperature pockets in the mash tun, and the way to fix that is to stir more.

 

[TheMadKing]

If those are your results, you need to stir more during your dough-in. Any case of temperatures rising during the mash without adding heat is evidence of temperature pockets in the mash tun, and the way to fix that is to stir more.

I tend to agree. I measure my mash temp after several minutes of stirring and every 20 minutes and I've never observed anything but a slow temp drop. Maybe I just have a really crappy mash tun though? I just built a new mash jacket so maybe I will start seeing temp rises with better insulation.

 

[MagicMatt]

I tend to agree. I measure my mash temp after several minutes of stirring and every 20 minutes and I've never observed anything but a slow temp drop. Maybe I just have a really crappy mash tun though? I just built a new mash jacket so maybe I will start seeing temp rises with better insulation.

I hear y'all but not sure what to say. Other than maybe it just takes a few minutes for my thermometer to adjust?

I use a wooden mash paddle and stir the bejezus out of it while I have someone else slowly pour the milled grain. I use a 10g Igloo round cooler with domed false bottom. I don't preheat. I usually overshoot my strike temp by a couple degrees, dump all at once into my MLT, drop in a floating thermometer (the same one that was just in the kettle with the strike water) and close the lid while I mill my grain (2-3 minutes). When I open and read the temp, I'm either spot on or 1 degree over. Either way I dough in, and continue to stir for a good 60-90 seconds afterwards, making sure to get all the way to the bottom as well. Drop the thermometer back in and close it up.

Five minutes later, it shows about 5°F lower than my desired mash temp. At 10 minutes it's 50/50 that I'm either right on my temp, or a degree(ish) below still. At 15 mintues I'm always right on, and I lose a fraction of a degree on average over the next hour.

I've only very recently gotten a Thermapen clone that's really accurate but only 1/4 the cost. So far I've only used it for one brew, but I did not use it to check the initial mash temps (only near the half way point and the end). Next brew I'll check to see if it's just lag from my floating thermometer.

 

[MagicMatt]

I tend to agree. I measure my mash temp after several minutes of stirring and every 20 minutes and I've never observed anything but a slow temp drop. Maybe I just have a really crappy mash tun though? I just built a new mash jacket so maybe I will start seeing temp rises with better insulation.

I hear y'all but not sure what to say. Other than maybe it just takes a few minutes for my thermometer to adjust?

I use a wooden mash paddle and stir the bejezus out of it while I have someone else slowly pour the milled grain. I use a 10g Igloo round cooler with domed false bottom. I don't preheat. I usually overshoot my strike temp by a couple degrees, dump all at once into my MLT, drop in a floating thermometer (the same one that was just in the kettle with the strike water) and close the lid while I mill my grain (3-5 minutes). When I open and read the temp, I'm either spot on or 1 degree over. Either way I dough in, and continue to stir for a good 60-90 seconds afterwards, making sure to get all the way to the bottom as well. Drop the thermometer back in and close it up.

Five minutes later, it shows about 5°F lower than my desired mash temp. At 10 minutes it's 50/50 that I'm either right on my temp, or a degree(ish) below still. At 15 minutes I'm always right on, and I lose a fraction of a degree on average over the next 45 minutes.

I've only very recently gotten a Thermapen clone that's really accurate but only 1/4 the cost. So far I've only used it for one brew, but I did not use it to check the initial mash temps (only at 15 minutes and the end). Next brew I'll check to see if it's just lag from my floating thermometer.

 

[mattdee1]

I see this happen, too. I use a cheap analog glass-tube thermometer in my mash; I just drop it in there and put the lid on the cooler. Normally what I do is let it sit in the mash for 10 minutes and then check the temperature. There was only once when I was compelled to adjust the mash temperature based on this initial reading. Just about every time, after I put the lid back on and check the temperature at the end of the mash (40-50 minutes later), the reading on the thermometer is actually higher than the 10 minute reading.

I know there is no reason why the temp should go up, so I figured it was probably due to the slow rise time of the analog thermometer and/or some slow temperature distribution phenomenon. I also stir the crap out of the mash and it doesn’t seem to matter, I see the same rise every time. Now it’s part of my process to add 2 degrees to the 10 minute reading and consider that my “achieved mash temp” and it works pretty much every time.