Carbonation, a Lesson Learned

A while back I packaged, read bottled, a Koelsch.  It was a delicious green beer, perfectly clear after gelatin fining, cold from the lagering refrigerator so I used the bottling calculators basing the calculations on a 32 degree beer.
The equations for bottle conditioning rely on two sources of carbon dioxide.  The first is a contribution from the bit of residual yeast in the beer.  A beer can appear bright, that is, clear, and still have 100,000 cells/ml in suspension.  Bottle conditioning uses this yeast.  You add back a bit of sugar, generally in the neighborhood of 4.5 ounces, to the beer and let the yeast cells do their thing.  It’s such a small fermentation there will be no perceptible off-flavors generated.  The second source is the carbon dioxide dissolved in the beer.  The assumption is that the beer is saturated with carbon dioxide at the temperature of packaging.  A beer saturated with carbon dioxide at 32 degrees needs just a bit of sugar to prime where a beer at 68 degrees needs the full amount – very little carbon dioxide remains in solution at room temperature.
So I packaged the Koelsch using the priming equations at 32 degrees and got an under-carbonated beer.  What happened?  The beer was fermented completely quite a bit warmer than the 32 degrees I was “lagering” it so it wasn’t saturated with carbon dioxide.  I can fix this, I take the caps off, drop a couple of priming tabs into each bottle and recap, little risk since the beer has already got a bit of carbonation, but work I didn’t need to do.
Lesson learned, let the beer warm up to room temp before bottling and use the full amount of priming sugar.  There’s no question about priming that way.

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