Originally Posted by wired247
Ive never brewed a Lager before but I gave it a shot over the weekend. Starting gravity was 1.058 . Two days into it I'm down to 1.025 and its still fermenting hard. I'm using S-23 saflager yeast from the pack into the wort. I am running the brew at 49 degrees in the chest freezer. Like i said Ive never done a lager before and the ferment seems crazy fast to me but I aerate with O2 through a stone so this seems to be what my Ales do as well. Anyway is this the time to pull the carboy out for a diacetyl rest?
You can either do it when you're about 75% of the way to Fg (about 1.018-1.020) or wait until visual clues show that it's active but slowing down some. If you miss that period, and do it later, it'll probably still be fine. The thought is just to do it before the yeast go dormant.
Sometimes you don't even need a diacetyl rest- if you pitch cold, do a long primary, and don't use a notorious diacetyl producer, for example- but it never hurts to do one.