figuring mash temps for a system - Home Brew Forums

 Home Brew Forums > figuring mash temps for a system

04-30-2013, 03:17 PM   #1
mm1473
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Ok--decided to try my first all grain. I did all the math and figured I would need a strike water temp of 163 to do a mash at 152 in a preheated cooler using the following equation:

Strike Water Temperature Tw = (.2/R)(T2 - T1) + T2

So I did that--added the grain and was WAY low--145. Ended up having to add a little more than 1/2 gallon of near boiling water to get up to 151 and quit there because I was worried there would be too much mash water. I stirred the crap out of it while adding that water so I am pretty sure that is an accurate temp.

So--I did some math and subtracted 163-145 to see how many degrees I lost to the whole system (grain and all). Then I divided that number by the lbs of grain to get 1.63 degrees of temp loss/lb of grain. Using this equation I should have had a strike temp of 170ish.

My question is--does this math make sense or is there some other way to figure the loss for the system.

Also--how much water is too much to add when raising the temp of the mash. I used about 1.3qt/lb as my initial volume and added a little more than 1/2 gallon.

04-30-2013, 03:26 PM   #2
brewkinger

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did you pre heat your cooler before mashing?
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04-30-2013, 03:33 PM   #3
mm1473
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yes--preheated

04-30-2013, 03:39 PM   #4
brewkinger

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what was the temp of the preheat water?
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04-30-2013, 03:48 PM   #5
mm1473
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Boiling--well a little less. I turned off the stove and was getting ready to fill the cooler with it and got a phone call. But it was pretty much boiling. I let it sit in the cooler while the strike water heated and drained just prior to adding the strike water. I figure I could not have preheated any more than that.

04-30-2013, 04:09 PM   #6
brewkinger

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Yeah the near boiling water would have enough.

My SWAG would be that you have discovered a specific of "YOUR" system.

Perhaps other wiser and more experienced members could chime in on this one. I have always wondered if certain grain types absorb more or less heat than others.

Hope that you get this figured out and perhaps we already have.
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04-30-2013, 04:18 PM   #7
Varmintman
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I have fought strike temps as well and found the grain temp plays a huge role in the strike temp. My grain storage during the winter gets rather cold and would screw me up every time. Screwed me up to the point I started to measure the grain temp and plug it into a strike calculator and found that my problems laid there.

Try using a strike water calculator and stick a thermometer in the grain beforehand.

04-30-2013, 05:59 PM   #8
brewkinger

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Quote:
 Originally Posted by Varmintman I have fought strike temps as well and found the grain temp plays a huge role in the strike temp. My grain storage during the winter gets rather cold and would screw me up every time. Screwed me up to the point I started to measure the grain temp and plug it into a strike calculator and found that my problems laid there. Try using a strike water calculator and stick a thermometer in the grain beforehand.
I knew that I forgot something!!! Blame it on my 2 children, they cause me to have a twitch and be forgetful.

The starting temperature of your grains plays a HUGE role in the thermodynamics of this scenario. If you start with grains at say... 65 degrees versus grains at 45 degrees, more heat is needed to increase the grains from lower temperature. I bet this could be the culprit and given that you were only off around 5 degrees or so to begin with, this could be an easy fix.
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04-30-2013, 06:32 PM   #9
SpeedYellow
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Quote:
 Originally Posted by mm1473 Boiling--well a little less. I turned off the stove and was getting ready to fill the cooler with it and got a phone call. But it was pretty much boiling. I let it sit in the cooler while the strike water heated and drained just prior to adding the strike water. I figure I could not have preheated any more than that.
Adding then draining boiling water is probably not the most repeatable process. IMHO a better & easier way is to add the entire strike water to the cooler, wait several minutes, then check the water temp in the cooler. Then track THIS temperature as your critical factor. Adjust as needed. Don't worry about equations-- experience is the answer. Just use a consistent process, then you need only adjust for grain temp on brew day.

For example, with my system using 1.5 qt/lb, I need the water temp in the cooler to be about 168F +/- 2F depending on grain temp. That will get me a mash temp of 154F. Doesn't matter how much grain. It's actually really simple once you've done a few batches!
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04-30-2013, 06:38 PM   #10
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Quote:
 Originally Posted by SpeedYellow Adding then draining boiling water is probably not the most repeatable process. IMHO a better & easier way is to add the entire strike water to the cooler, wait several minutes, then check the water temp in the cooler. Then track THIS temperature as your critical factor. Adjust as needed. Don't worry about equations-- experience is the answer. Just use a consistent process, then you need only adjust for grain temp on brew day. For example, with my system using 1.5 qt/lb, I need the water temp in the cooler to be about 168F +/- 2F depending on grain temp. That will get me a mash temp of 154F. Doesn't matter how much grain. It's actually really simple once you've done a few batches!
All of this. I lose 13 degrees total for 3 gallon batches and with my grain at room temp. It took me two batches to dial this in.

When I made 5 gallon batches it was more like 15-17 degrees.

Forget math. Just do it a couple times. Try to overshoot by a couple degrees because bringing it down is easier than bringing it up.
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