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Trouble with my mash temp

I am using my mash tun and it is having trouble keeping temp. I did a strike of 162 degrees and I was shooting for 148 degrees on a 90 min mash but it only wants to stay around 140 degrees. I keep adding 170 degree water but it really won’t warm up. Do I do my best to keep it warm as possible and just mash for 2 hours or is this mash a wash and I won’t get the conversion?


I Since I basically doubled the water amount of the mash I drained some out, heated it up, and put it back in the mash and now I am getting temp. This leads me to this question: What are the implications of a mash with double the recommended water amount? I used my sparge water so in the end I will end up with my projected amount of water and I am letting it mash for two hours.

You could have added boiling water instead of 170 F water to bring up temperature. As long as the combined temperature does not exceed 170 F, you won’t kill the enzymes. Also in the future, if you know you need a little higher temperature to get to the temperature you want, use hotter strike water, e.g., strike with 170 F water instead of 162 F.

The extra volume won’t hurt a thing, the starches will still convert to sugars just fine, etc. However, if you are skipping the sparge because of it then your efficiency will suffer quite a bit, so your original gravity will end up kind of low. You can fix this either by sparging and boiling for an extra long time, or boiling down to a smaller volume, e.g., if you’d planned on making 5 gallons, boil it down to about 4.5 gallons instead or something like that, if you still want to get a good original gravity. Or just beef it up with a little extract. All good options.

Thanks for the advice.

I normally mash in a kettle so this my first attempt at using my tun as a mash tun and I was not expecting that much of a temp drop but I knew I would need to use my sparge water to heat it back up. In the end my SG was 10 points under projected and my OG was 8 points under so it was a good learning experience. Chances are I have way too much room in my mash tun vs the amount of mash that is actually in the tun so there was lots of room for the heat to escape.

I usually use strike water of about 170-172 and then creep up on my mash temp. Then sparge with 190-200.

Also consider insulating your MT. It can be as simple as wrapping a heavy blanket over it or as elaborate as making a jacket of insulation.

It sounds like you may not have considered the thermal mass of the cooler at strike. Preheating it helps eliminating this effect, or adjusting whatever calculation or software to take this into consideration may help.

As for adding volume, I prefer a thin mash (1.8 - 2 qts / lb), but others will share other opinions. If you find yourself consistently undershooting target temperature, beginning at 1.25 to 1.5 is fine, and allows you to add volume without thinning it beyond whatever level you find to be acceptable. The previous comment about adding boiling water is correct; adding a small amount won’t have any detrimental effects.

Finally, I’ve seen this same thing happening with those who vigorously stir their mash when water and grain are combined. I stir quite a bit, but since it does indeed bring the temperature down a bit, I like to shoot for a couple of degrees above my target, and stir until I reach it.

Yes the amount of temp to “preheat” the tun is usually 6f during the height of the summer months and up to 12-15f in the extreme lows of a Minnesota winter.

So If I wanted 162 strike for 70f grain, I typically use the 8f figure for the preheat addition for most common brewdays. So 162+8 = 170 initial strike temp, transfer to cooler, leave lid on for a minute or two to ensure tun is good and heated. Then I find I may need to stir down a point or two or am spot on to lets say 162, mash in and find my strike temp on the money. Seal it up again and it usually will only drop a half to full point during 60 min on the norm maybe two if super cold out…like -15f cold.

I use a blue cube cooler as my mash tun. I started using a phone app “Brewzor Calculator” for 'Droid to calculate my temps. It takes the ambient temp of the grain, the weight of the grain, and the water volume used and calculates the strike temps. It’s been right on every single time for me.

I bring my cooler MT into the house the night before brewing when brewing in the winter, along with the grains, so both are a little warmer than my cold garage. Hitting mash temps is easier that way. When using a keg MT, I preheat with an electric bucket heater on a timer, so I start with well warm MT and strike water.

Decocting a little of the mash is always another option to raise the mash temp without further dilution.


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