### Author Topic: Eisbock math  (Read 835 times)

#### denny

• Retired with too much time on my hands
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• Noti OR [1991.4, 287.6deg] AR
##### Eisbock math
« on: October 10, 2015, 09:00:16 PM »
Just pulled the ice out of my first ever eisbock.  The bock was 6.63% ABV.  The ice accounted for about 25% of the total volume. So I'm assuming the ABV is now 6.63+ (6.63*.25) or about 8.28%.  Sound about right?
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#### S. cerevisiae

• Guest
##### Re: Eisbock math
« Reply #1 on: October 10, 2015, 09:08:29 PM »
It should be more like 6.63 / 0.75 = 8.84%.  You have the same amount of alcohol in 75% of the volume.

#### denny

• Retired with too much time on my hands
• Posts: 19858
• Noti OR [1991.4, 287.6deg] AR
##### Re: Eisbock math
« Reply #2 on: October 10, 2015, 10:10:15 PM »
It should be more like 6.63 / 0.75 = 8.84%.  You have the same amount of alcohol in 75% of the volume.

Thanks, Mark.  I always get that backwards!
Life begins at 60.....1.060, that is!

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#### MDixon

• Senior Brewmaster
• Posts: 1940
##### Re: Eisbock math
« Reply #3 on: October 10, 2015, 10:15:57 PM »
Or %ABVi x Vi = %ABVf x Vf rearranged to %ABVf = %ABVi x Vi / Vf

So exactly what he said if simplified

or

longhand assuming a 5 gallon starting volume and a 3.75 gallon finished volume: 6.63% x 5 / 3.75 = 8.84%
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#### brewinhard

• Official Poobah of No Life.
• Posts: 3250
##### Re: Eisbock math
« Reply #4 on: October 11, 2015, 12:27:52 PM »
How did you freeze the bock?  In a keg? Jumped the remaining bock into another keg?  How long did it take to freeze that portion?  I have been wanting to do one for a few years but have yet to have my chest freezer open for the freezing stage.

#### denny

• Retired with too much time on my hands
• Posts: 19858
• Noti OR [1991.4, 287.6deg] AR
##### Re: Eisbock math
« Reply #5 on: October 11, 2015, 04:51:59 PM »
How did you freeze the bock?  In a keg? Jumped the remaining bock into another keg?  How long did it take to freeze that portion?  I have been wanting to do one for a few years but have yet to have my chest freezer open for the freezing stage.

In a bucket.  I fermented in a bucket, then xferred t another bucket to freeze.  Made it easy to see what was going on and remove the ice.  I initially set the temp at 29, but it didn't freeze.  My controller/sensor may be off by a degree or two.  Frustrated, I turned it down to 23-24.  The next morning it was frozen solid!  I turned the temp back up to 26-27 and by the next afternoon it had thawed to the point where there was a layer of ice on top of the beer.
Life begins at 60.....1.060, that is!

www.dennybrew.com

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#### a10t2

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##### Re: Eisbock math
« Reply #6 on: October 11, 2015, 05:10:56 PM »
My controller/sensor may be off by a degree or two.

I'd say it's right on. To a first-order approximation, every 1% ABW drops the freezing point by 1°F.
http://www.engineeringtoolbox.com/ethanol-water-d_989.html
« Last Edit: October 11, 2015, 05:12:32 PM by a10t2 »
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#### denny

• Retired with too much time on my hands
• Posts: 19858
• Noti OR [1991.4, 287.6deg] AR
##### Re: Eisbock math
« Reply #7 on: October 11, 2015, 05:34:59 PM »
My controller/sensor may be off by a degree or two.

I'd say it's right on. To a first-order approximation, every 1% ABW drops the freezing point by 1°F.
http://www.engineeringtoolbox.com/ethanol-water-d_989.html

Thanks for that, Sean!  I was using an estimate I'd heard that 29F was the right temp. I'm gonna bookmark your link.
Life begins at 60.....1.060, that is!

www.dennybrew.com

The best, sharpest, funniest, weirdest and most knowledgable minds in home brewing contribute on the AHA forum. - Alewyfe

"The whole problem with the world is that fools and fanatics are always so certain of themselves, and wiser people so full of doubts." - Bertrand Russell