lefty913

Recipes 

I just bought an generic 5 gal igloo container and converted it into a mash tun. I have been testing out the temperature control ability of this cooler by putting in a known volume of water at a specific temperature and letting it sit for an hour.

To do so, I first add about 1 gal of 160 degree water (as a way of pre-heating the mash tun) and let it sit while I bring 2 gal of water to about 152 degrees. I then dump the 160 water (which by now is around 152-ish) and replace with the 152 degree water, close the cooler, and let sit for one hour. I have done this now about 5 times and each time the temperature drops about 10 degrees (after an hour the water drops to about 142 degrees).

My question is, obviously this experiment is performed without any grain, so I wonder if I add grain would the temperature not drop so much after an hour? That is, does the grain help stabilize the temperature? Not sure I want to waste grain testing this thing out...

Also, should I worry about this sort of drop? What are some people's experiences with temperature control using an igloo-type mash tun.

Yooper

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Grain and water hold the temperature better than just water. Plus, if it's a 5 gallon cooler, you'd want to have it pretty full to really gauge the temperature.

I have a 10 gallon cooler, and I preheat it with water that is close to 180 degrees. Those couple of gallons cool pretty fast, but then it hold the temperature very well afterwards.

Keep in mind that you'll preheat your cooler, and even then your strike water is about 11 degrees higher than your desired mash temp. Starting with 160 degree water in your experiment just isn't hot enough.

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ChshreCat

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More thermal mass will help keep the temp steady longer, yes. One point of heat loss though is the lid. The lid is hollow with a hole in it. I put a folded up bath towel on top of my cooler (same one you have) to slow the heat lost. Some folks will even fill the lid with some expanding spray foam insulation and have good results with that.

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scinerd3000

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+1 for spray foam. and i still use a blanket. With my 5 gallon cooler over 60 minutes i lose about on degree

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lefty913

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Thanks for the replies so far. I tried increasing the pre-heat water temperature to about 180 instead of 160. This resulted in a slightly less of a drop in temperature (152 -> 146), though not sure if it was this or because I put a towel on top of the cooler. I think I may get a can of expanding insulating foam to fill the lid -- I imagine this will help quite a bit.

DeafSmith

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Do you use the stuff labeled "For windows and doors", or the regular "Great Stuff" to fill the lid?

azscoob

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I used the regular great stuff, works pretty good for me! I put masking tape all over the top of the lid so when I shot the foam in and it oozes out the hole it doesnt stick to the lid, makes cleanup easier when it is dry.

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lefty913

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Hey Azscoob~ can you explain the size of the opening you are talking about in your lid? I don't see a hole in my lid, so I will probably make my own with a drill.

Do you have any pictures of your lid by chance?

EO74

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I have this same cooler with the lid foamed, i fill the cooler with very hot tap water for 10 min drain add the grain then strike water about 10 degrees above mash temp and i usually only loose 2-3 degrees in a 90 min mash!Watch out though u run out of room quick in the 5 gal cooler,but it suits my needs

smurfjuice

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how much grain will a 5 gallon cooler hold roughly?