I have a Coleman 70 Quart Xtreme cooler that I've modified for my mash tun. I seem to be losing a lot of heat out the top. Are there any good ways to insulate it to help prevent heat loss?

3 Answers 3


A towel on top helps prevent a lot of the heat loss. A plastic cooler, by itself, is pretty good insulation, though. In a single-infusion mash, you should only be losing a couple of degrees in an hour.

  • Yep, I add a blanket to the top. Seems to be enough.
    – sgwill
    Nov 14, 2010 at 12:49
  • Towel or blanket on top is the way to go. You will get better insulation though if you put a soaking wet towel on top.
    – Matt Utley
    Nov 14, 2010 at 15:05
  • @Matt I never heard that about a wet towel. That seems counter-intuitive. I mean, if I wrapped a wet towel around myself, I would expect to feel a lot colder than if I used a dry towel.
    – pkaeding
    Nov 14, 2010 at 16:41
  • The wet towel on the outside of the mash tun is better at insulating because the towel is saturated with water. It's thicker and has more density and retains more heat.
    – Matt Utley
    Nov 15, 2010 at 1:31
  • Thanks everyone, I've used a blanket before and it worked. I thought I had a bad cooler, but it seems pretty common. I'll just keep using the blanket.
    – Fanzoo
    Nov 16, 2010 at 13:54

You might want to test for leaks around the hinges. I had some warping on a cooler there that I used to bring to the beech. Pour some water in it, go outside, flip it over and hold the top on tight. If there are leaks, then you will probably want to put some foam adhesive strip around the lip of the cooler. Something like Scotch Foam Tape.

But Nick and swgill definitely have the simplest solution. And it always handy to have a towel. :)


I'm thinking you must have some sort of leak or crack in your cooler. I use one of those orange home depot coolers and it maintains a very consistent temp while mashing. Maybe try filling it up with hot water and see if the outside springs any leaks. If the top doesn't fit properly, maybe try a layer of that spongy tape along the rim and a weight on top.

The cooler I use is this one, btw. You can unscrew off the spigot and screw in a valve really easily as well.

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