I brewed an English Pale Ale with wlp-002 3 days ago. I just checked the gravity and it is 55% attenuated. The airlock is still bubbling slowly and the yeast is starting to flocculate. What do you think the chances are that I will get to my desired attenuation of 65-70% by just rousing the yeast and raising the temp a couple degrees? I have had problems with under attenuation in my last couple of batches.

That yeast tends to floc out quite quickly. I have noticed that even though the krausen drops it still seems to be fermenting happily away. What was your OG? What temps did you mash at, and what FG were you hoping to hit? Did you aerate properly? Did you pitch enough healthy yeast (starter?)? Are you confident that your thermometer is calibrated properly? Just a few questions to try to help guide you in the right direction.

But to answer your question, I would try to rouse the yeast 1-2x a day until fermentation is fully complete. Bumping the temps a couple degrees and holding it there can also help it finish out properly while cleaning up any diacetyl that that strain loves to produce.

Also most yeast strains, especially the highly flocculant English and Dry English strains don't usually fully attenuate in 3 days. Give it more time and let the yeast break down those more complex sugars.

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