Originally Posted by chuckpo
As someone who has only done ales before, I'm curious about the lagering process. From what I understand when you have a wort with yeast and you throw it into a fridge the yeast will go dormant and settle. However, lagering takes place at colder temperatures, as in a fridge. Does the lager yeast just not go dormant in the colder fridge temps, or does it just slow down? Also, what is too cold for a lager yeast?
(a) "lagering" is the extended cold storage process.
(b) lager yeast strains are distinct from ale yeast strains. The most important differences are that the former are bottom-fermenting and will work at lower temperatures.
(c) yes, most lager yeast will go dormant at what most people would consider to be "refrigerator temperatures" (37 degrees or so).
(d) what is "too cold" for a lager yeast depends on the specific lager yeast strain and pitching rates. Some traditional German fermentation techniques pitch massive quantities of yeast at very low (40 degrees) temperatures then warm fermentation up to the mid-40s for a very slow, extended fermentation. At what I consider to be "normal" lager pitching rates (1.5 million cells per ml per degree Plato), some strains (e.g. W-34/70) will work at 45 or lower, while others (S-23) struggle mightily at temperatures under the upper 40's (again--just my own experience, YMMV).
For new lager brewers, the key is to pitch lots of yeast a few degrees below fermentatation temperature, which should be in the bottom third of the recommended temperature range for the specific yeast strain being used. As you get more experience and confidence, you can push your ferm temperature lower to (hopefully) get a nice, crisp, ester-free beer, especially after extended cold storage.