Partial Mash Temp Issues

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RunBikeBrew

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I've been doing partial mashes for about a half dozen batches now. I use a 2 gal cooler with a grain bag. I've been getting some very odd temperature behavior in the mash tun recently. (I use two floating thermometers, both have been calibrated at 32F and 212F. I also preheat the tun with ~1qt of boiling water.)

Here are three recent cases:

1. 3.5lb grain, 4.5qt of 166F water = 153F mash (perfect!)

2. 3.5lb, 4.5qt of 163F water = 142F mash (expected 150F, WTF?), added 0.5 qt boiling water = 149F mash (good!)

3. 3.5lb, 3.2qt of 146F water (protein rest) = 120F (should have been 131F), added boiling water = 129F (OK)
Added 1.5qt boiling (sacc. rest) = 142F (expected 154F), added small amounts of boiling water a couple of times, only got to 149F.

I want better control than this. Anybody have a PM/cooler process that's really accurate on temps? Maybe put water in first, get temps right, then add grain?

(By the way, case 1 above was Yooper's Dead Guy Clone. We cracked open the first ones last night...easily the best beer I've ever made. Well done, Yooper!)
 

944play

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Exactly, use your strike water to preheat the tun. Add grain after temp has stabilized.

Also, don't ignore the temp of the dry grain.
 

imherb

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I have been doing partial mashes using a Presto Kitchen Kettle. Basically a Fry Daddy with an adjustable thermostat. Works GREAT! I can mash up to 3 pounds. Just have to stir consantly until next rest temp. is reached.
 

AFAJ Brew Guy

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I also do PM brews in a 2 gallon. I don't use a grain bag though. It has taken me about 6 batches now to figure out the temps in it, but I pretty much have it dialed it. The two things that I do that really make the difference is that I preheat the tun with hot tap water. I fill it all the way to the top. I let this sit while I am waiting for the mash water to heat. The other thing that I do is that I put a towel on top of the lid. This made the biggest difference as a lot of heat is lost through the top of those things.

Like others have said make sure you take your grain temp into account. I use the spargepal app for the iPhone to get my "target" temp and then I add 4-5 degrees to that number. You can also use the formula in How to Brew, I get the same results. This gets me within 1 degree of my target temps.

Hope this helps.
 

ArcaneXor

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I'll second what others have said: Pre-heat your mash tun with your strike water, adjust the strike water temperature for the temperature of the grain, and stir the mash well, giving it a couple of minutes to reach a stable temperature. I use Beersmith to calculate my temps, and usually end up within a degree or so of my target. Having some ice and a cup or two of boiling water nearby is good, just in case you need to do some adjusting.
 
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