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Low mash temp on my first partial mash

I brewed a partial mash kit for the first time, and of course messed up. The kit I brewed was John Palmer’s Elevenses partial mash. Previously I have only done extracts. I did the mash my 5 gallon brew kettle. My starting mash temp was 152 F. (Later I realized it should have been 154 F). I wrapped the kettle in 6 old bath towels. So I figured it would keep the temp fairly steady but at the end of the hour it was down to 145 F. Because the mash started 2 degrees low and dropped 7 degrees from there I put the kettle back on the stove and slowly raised the temperature. Using a low flame I kept the temp between 150-155 degrees for an additional 30 minutes.

So, how bad did I mess up? What can I expect the effects of the low mash temp to be? And did my attempt to compensate help or hurt?

No worries, you basically did a 2 step mash and your beer will turn out fine. Awesome beer by the way, it is a standard in my rotation.


I wouldn’t think the difference between 152 and 154 would be that great. With the temp dropping through the mash, though, my understanding is that it basically made the wort more fermentable. That could result in a lower final gravity and a somewhat thinner beer.

I did something similar a few months ago with a different recipe, except on purpose. I started the mash ~154 and just left the pot on the stove top to see how much the temp would drop and what effect it would have. It ended up ~145. I think the expected FG was around 1.013-15 and it ended up below 1.01. The beer was tasty but a bit thin in the body. It’s hard for me to say what effect raising the temp for an additional 30 minutes has, buy my guess is not much since you already mashed for 60 minutes. I think most of the “work” was done at that point.

My normal MO is to preheat my oven to 170F (the lowest it will go). I get the mash to whatever temp I’m shooting for and put the kettle (with the lid on) in the oven and turn the oven off. One hour later and the temp is maybe one-two degrees lower at most.

You did perfectly fine, and in fact you really didn’t even need to heat it up. Anywhere from upper 140s to low 150s is just fine for a mash temperature. Cheers!!


Whew! Thanks for the replies! Really put my mind at ease. I have been wanting to make this one for a year but wanted to get comfortable with extracts first. I figure anything with John Palmer and Lord of the Rings has got to be good!

And thanks for the tip Mabus. I’ll give that a try next time. What I like most about the oven method vs wrapping the kettle in towels is that it would be easy to monitor the mash temperature. I didn’t want to do that this time because I didn’t want to lose heat by removing the towels and lifting the lid.

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