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?
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!
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%
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.
I’d say it’s right on. To a first-order approximation, every 1% ABW drops the freezing point by 1°F.
Thanks for that, Sean! I was using an estimate I’d heard that 29F was the right temp. I’m gonna bookmark your link.