While ale fermentation at home can be done quite easily at room temperature lager fermentation had been a bit more of a challenge to get just right. These days we've got a few advantages and tricks to make everybody's favorite it's hot I'm thirsty beer easier to brew at home.
There are generally two types of yeast we ferment beer with, lager and ale yeast. While ale yeast ferments at the top of the fermenter in an ideal temperature range of 65-70F lager ferments at the bottom of the fermenter at cooler temperatures in the range of 50-55F. Because of this fermenting lager at home requires either a temperature controlled space like a chest freezer or refrigerator plugged into a thermostat to maintain the ideal temperature range or a space in the home that maintains that temperature range, usually your basement in the winter time. That said lager yeast will work at ale temperatures but will result a very different finished beer than one fermented in the typical range. We tried this at the shop once fermenting a split ten gallon batch both five gallons with lager yeast but one was fermented at ale temperature and the other in the ideal lager range. The cooler fermented Oktoberfest resulted in a very true to style crisp, clean, refreshing, albeit malty beer. The warmer fermented lager resulted in a beer with a pronounced richness of the malty character and more pronounced fruity esters that resembled more of an amber ale. Neither one was perceived as bad or off and I personally was astonished by how many customers preferred the warmer fermented one.
Lager is the German word for storage and lagering is a controlled decay at cold temperature, just above freezing, for the purposes of conditioning and clarification. Although a process commonly used to condition a lager it can be used on any beer style. For instance one could lager a saison. We lager beer to cold crash the beer which will precipitate down any particulate in the liquid and also to round out any sharp edges in the beer's flavor for more of a mellowed and drinkable beer. It's this technique that can take a lager fermented at ale temperature or faked somehow with an ale yeast the rest of the way to tasting much more like an example fermented with the traditional temperatures.
Pseudo Lager is that faked beer using a very clean fermenting ale yeast, today's favorite choice being Scandinavian farmhouse yeast called Kviek, specifically the Lutra strain. These yeasts are a game changer for home brewers because of their versatility specifically their very wide temperature range. In this specific application a pseudo lager fermented with Lutra Kviek at ale temperatures will still have very low to zero ester production resembling a properly fermented lager. Now employing the lagering technique will carry a pseudo lager the rest of the way to tasting as much like a cold fermented lager with that clean, crisp, refreshing beer one might like on a hot day or to go with a schnitzel and some sauerkraut.
Prost.