Long fermentation

[Zoltan]

I'm making the high-gravity IPA I always make (O.G. 1.078, F.G. 1.018). Usually I leave it in the fermenter 3 weeks, and the end of which there's no evidence of further fermentation. This time, however, at the end of three weeks the gravity was still about 1.019-1.020 and on day 25 now that there is still some evidence of fermentation happening (pressing on the plastic lid of the fermenter produces bubbles in the vapor lock; wait a few hours, same). Should I worry? Why is it slower? Temperatures are about the same as they always are. Do I need to wait until fermentation actually stops altogether before bottling, or would I be risking exploding bottles?

 

[Hoochin'Fool]

Check out this post: https://www.homebrewtalk.com/threads/life-hacks-for-homebrewers-add-yours.734361/#post-10414959


But that said, it's been 25 days, for a recipe you always (frequently?) make, and it's stopped 1 or 2 points higher than it typically does. It's almost certainly finished.

 

[dmtaylor]

I assume you dry hopped in the past week or so? Hops contain varying amounts of enzymes, which will slowly convert complex sugars to simpler ones that the yeast can ferment. Your latest crop of hops just has more enzymes than previous batches did. The yeast is keeping up with whatever your hop enzymes are doing to the sugars. This phenomenon is known as "hop creep". If this is the case, you'll just have to wait it out. Don't bottle too quick, or else you will indeed end up with gushers or bombs.

 

[Zoltan]

No dry-hopping, though now you mention it I made a couple of hop substitutions this time, as the store was out of my usual. Instead of Citra, Warrior. Instead of Strisselspalt, Sterling.