Mash Temps irritate me.

So, as the title explains this has become my biggest foe in brewing. I started doing 1.5 gal batches to test new recipes and cut the cost of doing so. I adopted the BIAB method, although I'm using a three gallon cooler for my mash.

Anyway to the brew this morning. I preheated the cooler with Boiling water for 10 minutes. Dumped out the water right before adding the calculated 166 Strike water (1.02 gallons) for a rest at 151. This is for 4.27 lbs of grain. I doughed in and shut the cooler for five. Came back and the water was 161!. I stirred it around again and moved the thermometer to a couple of places and it read 155. So I start thinking I just need to let it set and let the temperature settle. So I closed it and came back in 10 minutes. This time it's back to 161. (I left the glass lab thermometer in the cooler). I stirred and checked a few more places. It was all 152 or 151, except one corner I had know I stirred up at 158.

What's going on? I have the lab thermometer submerged up to a point while it sits in the closed cooler. I bring it up so the tip is half the depth of the total mash when I check several places of the mash. Just frustrated. I don't think I've ever been able to hit a temp right on but maybe once. Is my calculation wrong (double checked it with a phone app and beer alchemy)? Or is my method of reading the temp wrong? Or something else that's not right?

I know one of the draw back to a square MLT is hot spots in the corners. They are notorious for this. My advice would to be not to worry so much about one little area of the MLT and focus on the overall average temp that was held for the 60 minutes or however long you are mashing.

How much do you stir when you dough in? I don't use a square cooler, I use an old keg, but it's really important to mix thoroughly as you're finding out. I drove myself crazy when I started AG for the same reason you are. I just mixed mroe and worried less.

I'd stop pre-heating with boiling water. I almost wonder if your cooler walls are hotter than the strike/grain and are warming it up some. That or you need a faster response thermometer....

What I do is take the amount of strike water and get it to 175-180. Then put that in an empty cooler, close the lid and wait 5 minutes. Open up and check the temp. It still should be above the dough-in temp. Stir/wait until the water gets to your dough-in temp. Add your grains and go from there.
I use a 60qt cube cooler and don't have hot-spot issues.

integrator said:

I'd stop pre-heating with boiling water. I almost wonder if your cooler walls are hotter than the strike/grain and are warming it up some. That or you need a faster response thermometer....

What I do is take the amount of strike water and get it to 175-180. Then put that in an empty cooler, close the lid and wait 5 minutes. Open up and check the temp. It still should be above the dough-in temp. Stir/wait until the water gets to your dough-in temp. Add your grains and go from there.
I use a 60qt cube cooler and don't have hot-spot issues.

Click to expand...

That's the method I've seen used most often by the guys in my local club...

Definitely the boiling water preheat that is throwing you off (unless you've adjusted your strike calculations to account for a MLT that is at like 180 degrees).

The method integrator stated above is what I use and temps are spot on.

So you think even though I am dumping the pre-heat water before adding strike water the cooler is holding enough heat throw off the mash temp with 1.02 gallons of strike water?

I've used the pre-heat method on my 5 gallon batches with pretty good results. But these small batches, it just sin't working.

Yes. The cooler walls will retain heat, and with a much smaller amount of strike water, it will heat it up even faster. With your 5 gal batch, you have a lot more water to dissipate that cooler wall temp.
Try my method above next time. Actually I got my method from Bobby.

Sounds like it's worth a try. Thanks.

or just quit preheating your mash tun at all and mathematically account for temp loss. Beer smith has been accurate for me every time. I am normally exact on the temperature I shoot for. Sometimes its a degree off at most.

Mash temps drive me crazy whether I'm doing a half batch BIAB or a full batch in my mash tun!! ugh.

This is an interesting topic. Since I don't have a HERMS, mash temp is still this annoying issue, which I can't really control very well.

You're saying add water first, wait 5, then add grain. Interesting. I usually add water to grain.

Yea, I'm moving to put water in cooler, wait 5, adjust temp with cold/hot water or stirring and then add grain. Just haven't been consistent enough with the water to grain method.

I was getting crazy readings all over the place. It doesn't help that my thermapen reads horribly wrong when near steam...lol, ended up mashing my last beer for two hours; got fed up with crazy readings and took the dog for a nice long walk. Good beer That's when I learned that two of my thermometers weren't reading right, which probably accounts for some of the craziness I've been seeing.

Edit: I think that this could be a support group. I thoguht that I was the only one who's mash temps would irritate them. Everyone's like, yup hit 152F right on the dot. Then I open up my mash tun, well it's 154F here near the edge halfway down. 157F here further down, 149F here along the edge....hmmmm....stir like mad, get similar results....maybe a touch hot, add a bit of ice, stir like mad. Open it back up and get higher readings.....crack open a beer and stop caring, and then watch the beer come out very good still.

I’ve got a rectangular 52 quart Igloo. My process has changed in just the last 2 batches. I now add a couple of gallons of boiling water, let it stand for 10 minutes, then dump out. Afterwards, I immediately add the water for the mash then stir in the grain. My initial strike temps have actually been right on as tested in at least 3 different spots in the mash. The problem I am noticing now, my temps drop 4-6 degrees in 60 minutes.

Yeah, I was just frustrated. ....Maybe next time...it'll be alright.