Fermentation stopped and then started again

Question

Hey friends. So I'm working on my first home brew. It's been in the fermenter for 3 days. After the second day of vigorous fermenting and hardcore airlock bubbling, the krausen started subsiding and was like that for about a half day. Today the krausen is back to the top of my carboy, but the bubbling isn't quite as dramatic. I'm unsure as to why the fermentation seemed to stop for awhile then start again. Could something be wrong or is this just a natural thing? It seemed to be a little cold in my "brew room" at one point, so I turned the temp up a bit. Seems to be good now. Here's a pic...any advice would be appreciated on how to get a consistent fermentation.

Answer 1

Nick's answer suffices for your "is anything wrong" question, so I'll answer your other one - "any advice would be appreciated on how to get a consistent fermentation."

The one thing you should do before anything else is come up with a way to control your fermentation temperature. Assume the recipe says to ferment at 68F. If you can find a way to keep that liquid at 68F for the entire week or so, your beer quality will improve drastically. Once you've come up with a way to reliably control temperature, then you can start playing with fine tuning it - such as pitching at 65F, letting it come up to 68F over 12 hours, holding it there for three days, then letting it warm to 70F slowly over the next four days to ensure the yeast stay active and re-absorb all the crap they spit out into your beer while they were making alcohol. But that's a little more advanced. For now, come up with a way to keep the temperature consistent and within a few degrees of what the recipe (or style or yeast package) calls for.

For good info on controlling fermentation temp, check out this episode of the Brew Strong podcast with John Palmer and Jamil Zainasheff.

Answer 2

If everything's OK now, relax! Your beer is probably going to turn out great.

If the temperature went below 16C/60F for ales or somewhat lower (maybe below 6C/42F or so?) for lagers, the fermentation might slow down significantly, but as long as you get it started up again quickly (i.e., not leaving enough time for an opportunistic lactobacillus to 'f' your 's' up), it shouldn't be a problem.