Explosion, then nothing

[Painter]

I brewed a 5 gallon batch on Monday and used a starter that I had prepared the day before. By mid-day Tuesday the fermentation was so strong that it was coming out through the air lock (next time I think I might use a blow off tube). By Wednesday all activity had ceased. I can't believe that the fermentation was complete in that short period and I haven't yet taken a hydrometer reading. Any ideas on what may have happened.

By the way, I swirled the fermenter and put a brew belt on and now it is bubbling again.

 

[JonM]

I bet you just had a really aggressive fermentation, and the bulk of fermentation occurred over those first 24 hours. What was the yeast and temperature?

even if it looks like nothing's happening now, it's likely doing something - just much slower than before. Cheers.

 

[RM-MN]

Here's what is happening: http://www.brewgeeks.com/the-life-cycle-of-yeast.html

You've likely let the beer ferment warm and the yeast can go crazy over the sugars then. The next time you brew try keeping the fermenter cooler. I think you will like the results.

 

[Painter]

I used Wyeast 1056. My basement is pretty cool, typically 58 to 65 degrees, but I put a sleeping bag around the fermenter and so maybe it got too warm at the start.

 

[NewWestBrewer]

I used Wyeast 1056. My basement is pretty cool, typically 58 to 65 degrees, but I put a sleeping bag around the fermenter and so maybe it got too warm at the start.

The fermenting temp is generally 5-8 degrees warmer than the air temp so no need for a sleeping bag for you. Your basement is perfect temp.

 

[RM-MN]

The fermenting temp is generally 5-8 degrees warmer than the air temp so no need for a sleeping bag for you. Your basement is perfect temp.

This is often repeated but it really isn't always true. If your wort starts out in the low 70's, the yeast will get real active and yes the temperature will be the 5 to 8 degrees warmer but at lower temperatures the yeast just aren't as active and they don't raise the temperature by very much. When I start my beer at 62 degrees in a 62 degree room the fermenter temperature only goes up to 64 degrees, a 2 degree increase.

 

[BigFloyd]

This is often repeated but it really isn't always true. If your wort starts out in the low 70's, the yeast will get real active and yes the temperature will be the 5 to 8 degrees warmer but at lower temperatures the yeast just aren't as active and they don't raise the temperature by very much. When I start my beer at 62 degrees in a 62 degree room the fermenter temperature only goes up to 64 degrees, a 2 degree increase.

That's consistent with what I've observed and a very good reason to cool the wort a few degrees lower than the low end of the optimal range for the yeast being used before pitching and keep it in the cool range until it settles down.

Pitching warm and/or having the fermenter in a room with a temp at or above the upper end of optimal (with no effort to cool it) is when the fermentation tends to run several degrees over ambient.