brewerTristan wrote:It now looks like it might be fermenting a little more (visible yeast on the surface). Does this have a good chance of success? I feel like the change in temperatures can't be good. How long should I continue lagering for after it finishes up?
For future batches, the best way to ensure complete attenuation is to leave the beer on the primary yeast until you have reached terminal gravity. If you run into problems and have already transferred, there is less yeast to finish the beer up. I think some commercial brewers like the Dan have talked about transferring off the yeast with a couple of points left to go and finishing the fermenation cold, but I haven't tried this. It probably takes quite a long time.
You need to raise the temperature to finish out the fermentation. You're only dropping 10 points and the bulk of yeast growth has already occurred, so you will not get a noticable amount of ester production or funky flavors by raising the temp now. Since you don't have much yeast in there and it's a pretty hostile environment, it could take quite a while to get to TG. If it gets stuck, you can try pitching in a 1 pint starter at high krausen of any yeast, again the small amount of attenuation is not enough to get significant off flavors. Just ferment the starter at or below the beer temp to give them the best shot at knocking off the rest of that sugar.
As for lagering time, your palate should really be the final judge there. I've had lagers that were great right out of the fermenter, and some that took 4 weeks of lagering to be drinkable (especially if there was a lot of sulfur in the fermentation).
Last year I brewed 5 lagers with the JZ method (4 weeks primary at 50F then package), most of these tasted very good right away with no lagering, at least the 'normal' gravity ones. The problem is that I only have space for one fermenter in the fridge, so I wanted to try to get them into the package faster without sacrificing quality.
This year, I'm doing a primary at 50F until TG is nearly reached (7-10 days with a healthy yeast pitch), then raising up for about a week or so until I detect no acetylaldehyde or diacetyl. It's very important that you have a clean product going into the package, because in the best case it will take a long time to clean up, and at the worst you'll be stuck with an off flavor. Using this method I had a pilsner that was in the fermenter for 2 weeks at 50 and 1 week at 65 and did not start to taste really good until 4 weeks of lagering. Also had a dunkel at 50 for 10 days and at 65 for 7 days and tasted great right out of the fermenter. Grist bill, yeast health, and a host of other things are going to come into this equation, the best way to know for sure is to taste the beer as it lagers and drink it when it tastes good.
