New airlock activity after 4.5 weeks in primary.

I have an Autumn Amber Ale that I brewed a little over a month ago fermenting in the closet. It went fast and furious right from the start and then calmed down after the first week. After the 2nd week there was no visible activity in the fermenter and no bubbles in the airlock.

This morning I went in the closet to grab a jacket and the airlock was bubbling slowly but steadily and there was a little visible activity in the fermenter. It doesn't look infected but what else could cause this? The temperature has been relatively stable at around 67-70. Any ideas?

 

Changes in barometric pressure?

 

+1 Barometric changes/Temp changes/ A truck rumbling by on the street/The cat brushing against it/Vacuum Cleaner....Bubbling of an airlock, especially if it's been idle for awhile, is usually a product of changes in the environment, rather than anything else.

 

Very interesting I never would have thought of that. In the past week or so we've had all sorts of thunder storms and tornado warnings so that seems very plausible.

Will bottling now be inviting bottle bombs?

 

You need to check your specific gravity and see if it is stable over the course of a few days, if it is you are good to go.

 

No, you're thinking in terms of bubbling = fermentation.... Think of an airlock as it's supposed to be thought of, as a VENT a VALVE to release gas, NOT as a fermentation gauge. All that more than likely happened is gas that has been present ALL THE TIME in solution got released, either from it being trapped in the yeast at the bottom of the vessel, because of some physical shaking of the vessel or the room it is being stored in, or the change in barometric pressure putting pressure on the liquid in the vessel or a rise in ambient temp causing the co2 to expand beyond the layer that was in the headspace.

It's probably not fermenting again, more than likely it's off gassing. You won't have bottle bombs or anything like that. You're not increasing the amount of co2, what's happening is the already present co2 is working itself out.

That's what so many brewers into trouble, they keep thinking an airlock is a fermentation gauge, that any time it acts up or doesn't act up they think fermentation is or isn't occurring. If you think of it as it's REAL purpose, as a release valve to keep the beer off the ceiling, then you realize that you dealing with gas which is fluid in it's own right, it expands, contracts, and comes out of solutions form many reasons beyond JUST fermenting....

 

Use the Force Luke. And by force I mean hydrometer. The airlock is like the targeting computer that Luke turns off and ignores.

(Wow, that's a bad analogy)