My fermentation process is a mashup of several different methods, both traditional and innovative, from a variety of sources.
Fermentation begins with the yeast starter. My starter process is a little different than most, and is based on the drauflassen and kräusening methods used by German breweries. While I’m transfering the cooled wort from the boil kettle to the carboy, I draw off around 10% of my batch volume into a small glass fermentor. This volume of wort will serve as my yeast starter/activator, and will be used to inoculate the main batch of wort. The small fermentor receives the yeast pitch for the batch, and is fitted with an airlock and shaken to aerate before being placed in an area slightly higher than the target fermentation temperature.
I shake the carboy to aerate, then place it in the fermentation chamber – a 1960’s-ish GE refrigerator. The fridge and heat source, a hair dryer, are controlled by an STC-1000. I tape the controller’s temperature prob to the side of the carboy, then it usually takes 4 hours or so to reach lager pitching temperature.
After the wort has cooled to the intended fermentation temperature, I shake the carboy again to ensure sufficient aerarion. Somewhere between 4 and 24 hrs after preparing the yeast starter, it will be into krausen. When both the wort and the starter are ready, I pitch the entire contents of the starter into the main batch of wort, save for the last bit of trub. This method seems to shorten the lag time before I see active fermentation, but I mostly do it because it’s easy and I don’t want to spend a bunch of money on a stir plate, flask, etc. Maybe I’ll change my method somewhere down the line, but it works for me.
I leave the chamber set at pitching temperature until the beer reaches high krauesen, usually 3-6 days, depending on the yeast strain.
When the foam on top of the beer seems like it’s reached its highest point and is covered with scum, I’ll move the probe from the side of the fermentor to a pint mason jar of water placed in the chamber, so it measures the ambient temperature and not the beer temperature. I then bump the temperature setting up a few degrees, to the middle or high end of the yeast strain’s recommended range.
When fermentation starts slowing down significantly and the foam cover is receding noticeably, I again bump the temperature up for a diacetyl/conditioning rest, as outlined by Braukaiser.com. I typically hold the beer at 22°C/72f for about 3 or 4 days.
When FG has been reached and all fermentation activity has stopped, I drop the temperature for lagering. I set the controller for 0°C, but the fridge usually shuts itself off around 2-3°. After some time at lagering temperature, the beer is kegged and fined with gelatin, and the yeast cake is harvested for future brews. The time spent lagering in the chamber depends on how soon I need the chamber for the next batch. I prefer to give it at least 2 weeks, but sometimes I’ll move the carboy to the keezer (also at 2°C) if there is room. As a last resort, I’ll keg the beer early, and hold off on the gelatin for a week or two.
Using this method, I can turn around pale lagers in 3-4 weeks easily, grain to glass. Most of the lagers improve with more time spent at lagering temperature, up to a point. 6 weeks from brew day is generally the peak of flavor and freshness for my light lagers.
Further information on lager fermentation schedules can be found at Braukaiser