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Old 12-20-2012, 08:53 PM   #1
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Default Mash Tun Heat Loss

I have a new 48 QT igloo marine cooler, and I'm trying to plan out my brew day configuration. First brew has 12 lbs of grain. With that much head space do you think it will drop much in temp? I'm thinking about reinforcing it with some additional insulation be required for a stable temp? I always preheat the tun for about 5 min before mash in. Also planned on putting it in the sun. Thanks for the advice!

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Old 12-20-2012, 09:28 PM   #2
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I normally have a lot of headspace in my cooler for average beers. If I pre-heat and cover the mash with a sheet of aluminum foil I lose no more than 1 degree during the mash.

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Old 12-20-2012, 10:15 PM   #3
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I've tried one of those microwave massage pads and placed it on top of cooler lid, then wrapped around the whole cooler with sleeping bag. Most heat is lost from lid and the pad stays warm for about 1/2 hour. Can microwave again for 1 minute as needed during mash. Couple weeks ago I mashed 5 gallon batch in 52 qt rectangular with lots of head space and only lost 1 degree over 60 minutes. Simple but works.
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Old 12-20-2012, 10:17 PM   #4
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If you strike at the correct temperature, and hit your desired mash temp, heat loss should be negligible.

Just get that lid on tight and relax.
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Old 12-20-2012, 10:21 PM   #5
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You can do a number of things. I add 180-185* water and let it sit until it starts to come down near my strike temp. I then dough-in above desired strike temps and stir like a beast with a wire whisk until I reach mash temps. Then I close the lid and cover with two blankets. I don't lose even 1* over 60m mash, even with just 20lbs. in a 70qt cooler.

Others wrap the lid/top of cooler with saran wrap to mitigate air coming in/out. The foil over the grist is also supposed to help. As BM said though, it's negligible if you lose a degree or two.

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