[denny]

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?

[S. cerevisiae]

It should be more like 6.63 / 0.75 = 8.84%.  You have the same amount of alcohol in 75% of the volume.

[denny]

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!

[MDixon]

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%

[brewinhard]

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]

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.

[a10t2]

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

[denny]

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.