General Category > Extract/Partial Mash Brewing

Partial Mash Brewing using Homemade Mash Tun


Fellow Brewers.

I converted a 10 gallon circular igloo cooler into a Mash tun and have brewed one batch with it...I'm I was wondering if anyone has any straight forward instructions on how to brew a partial mash with this type of converted mash tun.  For me, the biggest issue was getting the temperature in the mash tun up to where I needed it to be.  It seemed like it dropped 10 degrees when I transferred the water from the stove into the mash tun.  This didn't seem right to me...I would add hotter water to try to compensate, but still didnt seem like I was doing it correctly. 

Anyone care to help a brewer out?!


The temp/thermal mass of the grain and cooler need to be taken into account.  This can be done w/ brewing software or you can just take good notes of how your system works for your next brews.

For me I usually need to be 10-16F hotter depending on the temp outside and the thickness of the mashh.

right on - that sounds like a good plan.  Should I put the water in the tun, then add grains or vice versa?

It's a bit easier to make sure all the grain is wetted if you add the grain to the hot water in your cooler.  
Doing a few brews and playing with the hot water temps needed will help you figure out your system.  I preheat my cooler with a gallon or so of really hot water, dump it out and then I just add about 12 - 13 degrees to my desired mash temp and add my mash water ("hot liquor") at that temperature.  Brewing with your system will help you figure out what works best for you.

Best bet for you might be to first..

Decide what temp you want you strike water to be.  Brewing software like Promash or Beersmith can do this for you.  Also a program someone distributed called MashWater.  Or you can just guess and use 12-13 (like Gail said above) degrees higher than your desired mash temp.

second... heat your strike water to 10 or so degrees higher than the temperature you came up with in the first step.  Dump this water into your cooler/tun and monitor its temp.  Once you lose the 10 degrees that you said it took for preheating the cooler, you should be down to your desired strike temp AND the cooler/tun is preheated.  Dump/stir in your grains and things should eventually settle down to your desired mash temp.


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