Some of the most common beer fermentation problems I see new brewers come across are 1) beer doesn’t start fermenting right away 2) beer starts fermenting too soon…
The first problem is usually the one new brewers worry about the most… if they don’t see their airlock bubbling, they immediately begin to think of reasons why…
They pitched the yeast while it was still at 80 °F, they forgot to add irish moss, they took longer than expected to cool… etc…
I’ve heard them all…
But the main reason why the airlock doesn’t start bubbling right away it’s usually because of lack of oxygen in the wort and not using ‘active yeast’…
Most brewers will pitch yeast right out of the vial and that is not ‘active yeast’… which is why I strongly recommend brewers make a yeast starter or re-use yeast… this is key to brewing better beer…
What concerns me the most when a new brewer ‘thinks’ their beer is not fermenting is that they immediately begin to think of ways to ‘fix it’ without making sure their beer is truly not fermenting…
Airlock activity can be a good indicator, but to really find out if your beer is fermenting, you must take a gravity reading…
When you take a gravity reading 2 or 3 days in a row, you’ll see your gravity drop as the yeast eat sugars and turn them into alcohol… if you don’t see your gravity readings drop, then you may be one of the few brewers who does actually have a problem with their beer not fermenting… at which point, pitching more yeast would be recommended…
If your beer starts fermenting too soon, then once again, you want to take a gravity reading to make sure that fermentation is indeed complete… sometimes the airlock will stop bubbling, but your gravity will continue dropping as fermentation can continue a few days after bubbling ceases…
Brewers that have this problem usually have it for two reasons… the first is not pitching enough yeast or active yeast or both… which is another reason why I recommend using a yeast starter or re-using yeast…
The second, and possibly the most common is because they do not control the fermentation temperature… yeast are very sensitive to changes in temperature… a change in one degree is like a change of ten degrees for them…
If you leave your fermentor in a basement or somewhere where the temperature can swing up to 20 or even 40+ °F, then the drop in temperature at night will usually cause the yeast to go to sleep and fermentation can stop… again, take a gravity reading to make sure, and if needed, warm up the fermentor and move the yeast around to re-start…
Better yet, control the temperature of your fermentor…
Cheers!
