beer started fermenting again after 2 and 1/2 weeks?

[biggben]

okay i just brewed a brown ale and its on day 21 and about a week ago the airlock started bubbling again. i was unaware because i left it at my mother in laws house, but she said it has been bubbling for about a week now. when i opened the bucket to look at it to see if it was infected it had a head of krausen it also attenuated a little more bringing it from 5.4 to 5.8. it has recently got warmer here by about 10 degrees would this be the reason for it fermenting again? the sample tasted great but i am still worried that it might be infection! has anyone had a batch start fermenting again after two or three weeks? and did it turn out good or not?

 

[Suthrncomfrt1884]

If there's a temp drop that is drastic enough to cause the yeast to go into "hibernation" (or you were fermenting cold to begin with), then there's more than likely leftover sugars that need to be fermented. If this is the case, then yes, a temperature increase would probably restart fermentation.

 

[beerkrump]

Warming a beer in a fermenter does three things that can cause the air lock to bubble.
1) The release of CO2.
2) Increase in internal pressure as the existing gases expand due to the change in temperature.
3) Yeast may ferment a little more.

In all three cases, it's still beer and your mother in law will enjoy it.