Question for users of cooler tuns

I just purchased a 10 gallon rubbermaid cooler from Lowe's. I tested 6 gallons in it at 162 degrees for an hour with blankets on top. It ended at 158. I've read that some fill the lid with foam to help heat loss. This may even be better?

My question is, for those of you who've gone that route, are you happy with results? Or should I return this cooler and look into one of those more expensive coolers that make claims about holding temp for long periods of time. If you had it to do all over again, what would you do?

Thanks in advance.

I'm no scientist, but I believe you'll get better heat retention when you have 10-13 pounds of grain in there as opposed to just hot water. The grain acts as its own insulation.

Naggs said:

I'm no scientist, but I believe you'll get better heat retention when you have 10-13 pounds of grain in there as opposed to just hot water. The grain acts as its own insulation.

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+1 to this. I loose maybe 1 or 2 degrees max on a 60 minute mash with my 10 gallon igloo. Also, pre-heating the tun helps a lot.

+1 What Naggs said. I usually start out with near boiling water in my cooler and wait for it to drop to the strike temp. This can take an hour but can be speeded up by opening the lid and stirring the water. The idea is to get the cooler well preheated (oxymoron). Once you dough in, the mash will hold within 1 or 2 degrees for a full hour with the lid closed. Don't forget to factor in the temp of your dry crushed grain to end up with the correct mash temp. Sorry muthafuggle, you beat me to it.

Oh yeah, mine is a cheap cooler. On cold days I'll wrap a blanket around it. It works fine.

Gotta preheat that sucker. I preheat mine with 180F water for 30 minutes, then if it's still above strike temp, I'll "stir it down" or even add a touch of cold water.

9 out of 10 brews, I loose less than a degree.

Boodlemania said:

Gotta preheat that sucker. I preheat mine with 180F water for 30 minutes, then if it's still above strike temp, I'll "stir it down" or even add a touch of cold water.

9 out of 10 brews, I loose less than a degree.

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Yep, me too. Add 180 degree water and let sit while you crush your grain. You should be at strike temp. If you're in a hurry, you can preheat with one gallon of hot water and cover it for 10 minutes, then drain. But I like adding all of my strike water and letting the temp come down to strike temps- it is easy, and it seems to really preheat the MLT perfectly. It will only lose a degree or so over an hour.

As was mentioned, the grain also helps insulate and unless you're doing a tiny grain bill (under 7 pounds), you won't need to worry about the headspace in there.

+10 to the suggestion for preheating the mash tun... I was losing 4-6 degrees initially until I figured that out...

Thanks for the replies. Here's a little additional info.

My actual test first involved 3 gallons and no blanket and I lost over 15 degrees. I then reheated the 3 gallons to 165, closed the lid. Heated another 3 gallons and added that and then blankets. So in a sense I think it was preheated? But maybe not high enough. Loss was 5 degrees.

The Rubbermaid coolers don't melt/warp with boiling water?

I also noticed the sides weren't warm but the top was. Heat rises, so would grain slow down heat loss from the top? This is what made me wonder about foam in the lid to help.

+another1 I just overshoot my strike temp by 10F and let it sit until I get to where I want it.

I did pour 5 gallons of boiling water into my cooler one time when I wasn't paying attention to the strike water temp. It didn't warp or anything. Even the food grade buckets can take boiling water. I wouldn't move them though...

Yes, they will warp/crack with boiling water. I have proof. But you're totally safe with 180 degree water.

Yooper said:

Yes, they will warp/crack with boiling water. I have proof. But you're totally safe with 180 degree water.

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Lol...ok. I won't do that again!