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Old 04-14-2012, 10:33 PM   #1
ASantiago
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Default Mash temp increasing on its own?

What I'm describing below has been consistently happening for every batch I've brewed in the last year.

Why does the end temperature of my mash end up higher than the beginning temperature?

  1. I have a 10 gallon round cooler (the typical orange type from Home Depot), with a false bottom, etc, which I use for mashing.
  2. I take both the grains and the cooler out to the garage about two hours before mashing to let their temperature stabilize (I brew in the garage).
  3. I measure the temperature of the grains and enter that into BrewSmith so it can figure out for me the initial temp of the mash water before putting it into the mash tun.
  4. Five minutes after I put the water into the mash tun, I measure the temperature. Let's say it's 152F and it's where I want it to be.
  5. 30 minutes into the mash, I measure the temperature again. Invariably, it's about 4F over the initial measurement and above where I wanted it to be. This temperature usually holds until the end, although sometimes it may be higher by a degree or two by the end.

What's going on? I figured five minutes of settle time should be plenty. And in any case, why would the temperature *increase* over time? If anything, I can see it decreasing. Enzimatic activity doesn't generate that much heat, if at all, does it?

This has me very, very puzzled.
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Old 04-14-2012, 10:45 PM   #2
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Tough to say, but when I'm starting my mash, I usually end up overshooting temps by just a hair, so I end up stirring quite a bit until I hit my target temp. I think stirring gently helps equalize hot spots. Usually I will check multiple areas in my mash tun to get an average. My final (60 min) temps are typically either the exact same as start or sometimes 1 degree lower.

Are you using a probe thermometer?

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Old 04-15-2012, 02:03 PM   #3
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I use a floating glass type of thermometer.

Maybe I'm not stirring enough. But my concern with stirring more is that the software calculated a specific temperature for the water given the current temperature of the grain and mash tun and their respective thermal mass. I could be letting too much heat go.

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Old 04-15-2012, 02:11 PM   #4
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I always stir my mash before taking its temperature. This evens out the water temperature between the hotter water on top and the cooler water at the bottom.

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Old 04-15-2012, 02:18 PM   #5
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You gotta stir it up good. No way around it unless you recirculate. The temp isn't rising on you, it just didn't get stabilized before you took your initial reading. Either that, or you didn't give the thermometer enough time to adjust before you read it.

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Old 04-15-2012, 02:19 PM   #6
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Sorry guys, I don't think I was clear enough. I do stir the mash after putting in the water. I do it for a minute or two and try to mix it up well. The first temp reading I take, 5 minutes in, is after I've stirred the mash.

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Old 04-15-2012, 02:21 PM   #7
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are you using the same thermometer for all the measurments?this seems odd.i used the same type of mash tun you are for quit a few batches and i always had an initial temp drop,hhmmmmmm.maybe you need a new thermometer?i used and still do for calibrating my probe therms the floating type/dairy therm and i have noticed that it does need a good amount of time to get an accurate reading.

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Old 04-15-2012, 02:42 PM   #8
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Did you stir the mash before you took the temperature 30 minutes into the mash?

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Old 04-15-2012, 02:45 PM   #9
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I do use the same thermometer for all mash temp measurements.

Indeed, if any change at all would be expected, it would be a temp drop.

Do you think the thermometer needs more than 5 minutes to level off? I put it in right after I stir the mash, close the mash tun, and then set the timer for 5 minutes. After I read it, I leave it in until the very end, so by the time I take the mid-point measurement (30 minutes or so), it's been sitting there for a good while.

The funny thing is that you'd expect the temp to be really high initially. So, if the water in temp is supposed to be 164F so it stabilizes at 148F (my last batch), you'd think the 5 minute reading may be something like 155F if I don't stir well, with a 30 minute reading below that. Instead, I get a 149F reading at 5 min and a 153F reading at 30!

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Old 04-15-2012, 02:45 PM   #10
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Quote:
Originally Posted by BobC View Post
Did you stir the mash before you took the temperature 30 minutes into the mash?
No, I don't. Should I be?
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