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Igloo Cooler - Trouble Holding Mash Temp

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vallonswayla

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Hey All-

I am doing small batch MIAB(2.5-3 gallons), and have had trouble holding mash temps in my cooler(link to my cooler below). I had done 5 gallon MIAB batches before in a 10 gallon home depot cooler which held temps great, but this cooler doesn't seem to hold temps very well. Any suggestions? Home Depot also sells a smaller 5 gallon cooler, maybe that's got better insulation on the sides or at the lid.

Here is what I have:
 

McKnuckle

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No suggestions other than that I have the standard Igloo branded, red and yellow version of that cooler and I agree with your assessment. It's "fine" but always loses a few degrees, even when I heat the water in it directly with a heat stick, cover it with a winter coat, and leave it in my 74 degree workshop next to the boiler.
 

slayer021175666

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I have 2. A 5 gal and a 10 gal. Both are rubbermaid brand. They hold quite well with a 1 degree drop at most. Preheating should help. Also, the lids on either brand are just air filled. Its good to fill them with canned foam insulation or cover them with a sleeping bag or both, while mashing.
Another consideration is, you aren't filling it up much. The headspace and overall weight of the mash are a big part of heat retention.. The less headspace in the tun, the better. But, the more important factor is the weight of the mash. The mash acts as it's own insulation and the bigger amount (heavier) of mash there is, the more it self insulates.
Hope this helps, man.
 
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cubalz

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Try this: Pre heat the cooler with very hot water for 15 mins and then drain prior to mashing in with your strike water. I had the same problem back in the day when I was using coolers. This lessons the thermal wicking considerably
 
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vallonswayla

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So you just drill a hold in the lid on one side and fill with canned foam? Seal off with some kind of tape?
 
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vallonswayla

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Try this: Pre heat the cooler with very hot water for 15 mins and then drain prior to mashing in with your strike water. I had the same problem back in the day when I was using coolers. This lessons the thermal wicking considerably
I actually did do this, it seemed ok for about 20-30 mins but after that it started losing a degree every 5 minutes or so. Steady decline.
 

cubalz

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vallonswayla: I think you are worrying unnecessarily as most of the conversion happens in the first 30 minutes anyway.
 

slayer021175666

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I added to my statement above so, take a look at that too but, about insulating the lid:
Drill a few holes in the underside equidistant from each other in such a manner as to fill the center of lid first expanding out to the edges. The foam will gush out of the holes for quite some time so do this operation outside. When it stops coming out of the holes, Break off and clean up the excess. Last, cut the foam off flush with each hole. No tape required. Bam! Insulated mash tun lid. :)
 

jerrylotto

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When you are losing heat, measure the temperatures on the outside of the mash tun. If you have an IR thermometer, it is simple but any way you can take a survey of the surface temperature all around, you can find the hottest points and improve the insulation there.
 

Romex2121

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I also do 2.5 / 3 gallon batches and use a 5 gal. Igloo cooler , I lose maybe 1 ta 2 degrees in an hr long mash ,
One thing that I did was cut a circle
the Same diameter of inside of cooler of the silver bubble wrap stuff used to insulate hot water tanks
(Seen the idea on this forum) , I slide it down into the cooler and rest it just above the mash level , It helps keep the heat from escaping up into the upper part of mash tun not being used when doing smaller batches.
This has worked pretty well for holding the heat , pre heating mash tun helps a lot too.
I’m betting the cooler your using is less insulated than say an Igloo or bigger name brand cooler.....
 
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jerrylotto

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One thing that I did was cut a circle the Same diameter of inside of cooler of the silver bubble wrap stuff used to insulate hot water tanks
(Seen the idea on this forum)
Awesome idea! Just cut one out of 2" foam board and epoxyed a plastic sheet on the underside. Cut a 1/2" hole in the center so I can hook my finger through it and pull it out.
 

bracconiere

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Its good to fill them with canned foam insulation
thanks, have to try that out :mug:

The headspace and overall weight of the mash are a big part of heat retention.. The less headspace in the tun, the better.
so vallonswayla should use something like this for a 3 gallon batch?

 
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vallonswayla

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I am mashing with around 4 gallons of water to boil down to a little over 3 gallons. Usually have about 2.75 going in the fermentor. I don't think deadspace is a big issue with 4 gallons in a 5 gallon cooler.
 

slayer021175666

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I'd say all is well if you're using 4 gallons of water. Just preheat the tun and insulate the lid. It should be fine. The only thing I couldn't tell you is the thickness of insulation built into your cooler walls. I have only used Rubbermaids. It will STILL work fine though if, you wrap it in a blanket or something. I have used my Carhartt coat to insulate fermenters before and I think it would work great for you. Simply throw the heavy coat around your cooler mash tun and zip it up. You should insulate the lid but, the hood on the coat might cover the lid nicely, as well!
 

Romex2121

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Awesome idea! Just cut one out of 2" foam board and epoxyed a plastic sheet on the underside. Cut a 1/2" hole in the center so I can hook my finger through it and pull it out.
I would like to be able to take credit for the idea “ but that would be wrong ”
I seen it in somebody’s post on this site awhile back while browsing thru older post...
I was gonna use foam board or styrofoam before the silver bubble wrap stuff but I was worried about little pieces of the exposed edges coming off and falling into the mash.
I’m curious to see how it works out for you , I know It helped with heat retention in my 5 gal. cooler ..
 

-Dan-

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Thought of a smaller cooler? Probably too big for the small batch. I used to have a similar problem for a while with a different setup years ago
 
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