Expert: Spencer W Thomas - 4/10/2008

Question
I was just wondering if there is a noticeably sign when it is done brewing, other then measurements, I take measurements, every so often but I don't know the limit on the yeast I used I would like to know if there is a way of telling when it is done, thank you.

Answer
Are you asking how to tell when fermentation has finished?  The most reliable way is to measure the specific gravity.  Fermentation is almost certainly done when the specific gravity hasn't dropped from one day to the next.  Generally, you can also tell because there are no more bubbles coming out of the airlock.

It can sometimes seem that fermentation has finished if you let the temperature of the fermenting beer drop too much below room temperature, which can cause the yeast to stop working.  If you think it may have stopped early, you can take a small amount, using a sanitized turkey baster, and put it into a beer bottle.  Cover the bottle top with foil and put it in a warm place (above the fridge is usually good) for 24 hours.  If the specific gravity in the bottle drops a lot, your beer is not finished fermenting, and you'll need to warm it up a bit so that it can finish.