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-   -   New Mashtun - mash temp, correct water volume... (http://www.homebrewtalk.com/f36/new-mashtun-mash-temp-correct-water-volume-358834/)

spleefy42 10-04-2012 09:10 PM

New Mashtun - mash temp, correct water volume...
Hi everyone,

I'm hoping someone can point out a flaw in my system here. I recently switched from a five to a ten gallon cooler mashtun. I'm having a lot of problems hitting my mash temperature. I'm using 1 1/4 quart per/lb and pre-heating the mashtun with boiling water before I mash in. For example.

I'm making a porter, and went with 10.5/lb of grain shooting for a mash-in of 154. Using 3.5 gallons, I heated my water to 166, dumped the pre-heating water from the mashtun, poured the strike water in, dumped the grain in, stirred briefly and tried several temp readings. 140 degrees, unless I was making contact with the grain, then it was like 120. What am I missing?

Thanks for any help!

FuzzeWuzze 10-04-2012 09:36 PM

I say you need a new thermometer.

In an UNHEATED Igloo cooler tun i routinely do 13# grain bills with 4 gallons of 162-163 degree water and it hits 150 every time.

If yours is preheated you should be way higher, the only thing i can think of is

Bad thermometer
Your grain is super cold(refrigerated? Left outside in cold garage all night?)

If your preheating your tun through 166 for 154 degree water may actually be too high...hard to say.

duboman 10-04-2012 09:44 PM

+1 to all above!
IF you are using a good calibrated thermometer and are not dumping in cold grain you should not be having this problem:)

Nagorg 10-04-2012 09:49 PM

I have an Igloo Marine 48Q converted into a mash tun. I have to heat strike water to ~170, add it to the MLT and let sit for ~5-10 minutes then dough in with grain that should be ~72-75. This gets me around ~154 and I loose about 4 degrees over the 60 minute mash.

spleefy42 10-04-2012 10:31 PM

FuzzeWuzze, I think you're right about the thermometer. After an hour I checked for conversion and it was completed. That, combined with the few small splashes I received on my hand while stirring, there's no way that water was only 120... Thanks!

BBL_Brewer 10-04-2012 10:48 PM

What I prefer to do is use the infusion equation instead of the strike water equation. Vi = (T2-T1)(0.2G+Wm) / Aw-T2 Where Vi = The infusion volume, T1 = starting temp of mash, T2 = target temp, G = Total grain in lbs, , Wm = the total amount of water in the mash in quarts, Aw = Actual temperature of infusion water. Normally this equation is used to calculate infusions. But, you can also use it to calculate your strike temp and account for heat loss by solving for Aw. To solve for Aw, the equation looks like this Aw = [(T2-T1 )(0.2*G + Wm) / Vi] +T2. In this case, T1 = your grain temp, Vi = your strike water volume in quarts and Wm will be used to account for your heat loss. Since the mash doesn't have any water in it yet, Wm would normally be zero in this case. But, you can convert your heat loss to an equivalent volume of water in quarts and use that value for Wm. For more information on equivalent volume of water and how to calculate it follow the link http://www.haandbryg.dk/mashcalc.html#heattun I don't know what your grain temp was, but I'll walk you through this.

We'll assume 70F for your grain temp. I ran your numbers from above and got an equivalent volume of water of ~5.2 quarts. You used 3.5 gallons, so that's 14 quarts.

According to the data you provided, we can calcuate what your stirke water temperature should have been to achieve 154.

T1 = 70, T2 = 154, G = 10.5 lbs, Wm = 5.2 quarts, Vi = 14 quarts

Aw = [(154-70)(0.2 * 10.5 + 5.2) / 14] + 154
Aw = 197.8 F So, according to what you've told us, your stirke water temperauture should have been ~ 198F.

198 seems pretty high for a strike temp, so Fuzze may be right, you might have a bad thermometer. Once you are sure you are getting accurate temperature readings, you should be able to dail this in real quick.

spleefy42 10-04-2012 10:59 PM

That, by far was the most intense answer to my question I could have asked for. More importantly, seeing the temperature determined backwards (to traditional logic), kinda makes me feel tingly. My inner geek bows before you.

FuzzeWuzze 10-04-2012 11:04 PM

Note, most digital thermometers like meat thermometers arent water proof. Ask me how i know.

I was using one blissfully ignorant, then one day i went to turn it on and it said it was 100F in my house, which was probably 70 at the time...i then pinched it between my fingers and it said 150F ..thank god for return policies even if i was at fault.

BBL_Brewer 10-05-2012 01:40 AM


Originally Posted by spleefy42 (Post 4470818)
That, by far was the most intense answer to my question I could have asked for. More importantly, seeing the temperature determined backwards (to traditional logic), kinda makes me feel tingly. My inner geek bows before you.

My inner geek likes to drink homebrew :mug:

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