Author Topic: Eisbock math  (Read 733 times)

Offline denny

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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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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.

Offline denny

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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!
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Offline MDixon

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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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Offline brewinhard

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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. 

Offline denny

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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.
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Offline 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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Offline denny

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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.
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