Chapter 11 - Priming and Bottling
11.7 Priming and Bottling Lager Beer
Ninety five percent of the time there is no difference between priming for lager beer and priming ale. But once in a while you will need to add fresh yeast for priming and carbonation purposes. This is most common when the beer is given a long cold lagering for more than two months. If the beer is very clear at bottling time, then the majority of the yeast may have settled out and there may not be enough left to carbonate the beer in the bottle. Prepare some fresh yeast of the same strain and mix it with the priming solution when you rack the beer to the bottling bucket. You will not need as much as you originally pitched to the wort, only about 1/4 - 1/2 cup of slurry for 5 gallons.
Since the yeast is being added for carbonation during the storage phase of the beer, there are a couple of differences in procedure from that used to ferment the original wort. Grow the yeast at the temperature you will be carbonating and storing the beer at (usually room temperature) instead of the original pitching temperature. This will produce more esters than the yeast normally would, but the percentage of sugar that is being fermented for carbonation at this stage is so small that the added difference in taste is unnoticeable. The reason for doing it this way is to avoid thermally shocking the yeast and to speed up the carbonation time. It is not necessary to store the beer cold after lagering. The beer can be stored at room temperature without affecting the taste of the beer.