by Dave Dahl – Lo Rez Brewing
Your brew day work is done and it’s time for the yeast to take center stage in the fermentation step of brewing. This is what makes wort into beer.
Yeast fermentation actually follows a very predictable multi-phase process. But to keep it simple, just keep in mind 1) fermentation starts immediately, 2) you’ll see it within 24 or 36 hours, and 3) it will take about a week to fully complete.
Once your yeast is pitched, snap on the lid, attach an air lock filled with vodka, and put it in a cool place like your basement or a chilly closet. Why vodka? Well it kills bacteria and foreign yeast, and it’s neutral in taste and aroma (which, if things are done right it shouldn’t matter….but if you brew enough you’ll find everything will fucking happen and therefore everything will eventually matter).
Check the air lock once or twice a day. What you’re looking for is bubbling and clarity. It will start bubbling after about 25 or 35 hours because yeast eats sugar, pees alcohol, and farts CO2 – crude but true. If the vodka evaporates, add more asap. If you *ever* see gunk in the air-lock that’s likely krausen forcing it’s way up the bottom…which means you’re facing imminent explosion. If you see that, and your week-long fermentation isn’t complete, open the lid and knock down the krausen a bit with a light spray of Star San – that’s far from ideal and you might pick up some off-flavors, but it might save your beer (and your closet) from a beer fermentation explosion.
Protip: Without checking the gravity of the beer, and comparing it to the starting gravity, you can’t be exactly sure when it’s done fermenting. But letting it sit for a couple weeks is a good rule of thumb. You can let the fermentation go longer, but *don’t* let it go shorter. It’s easy to err on the short-side and produce crappy beer, it’s hard to err on the long-side and produce crappy beer. Just like smoking a brisket, you have to find that sweet spot. If you don’t understand that analogy, you need to get down on more ManBQue.