Fermentation of my IIPA

[Paradigm]

Hi all, another stuck fermentation post. Our brew day was 2 weeks ago yesterday and our fermentation stuck at 1.020 starting last week. Since then we've had it at a steady 20C ambient and we checked the gravity yesterday and it was still dead on 1.020.

The OG was 1.072 and the target FG is 1.01 or lower. It was an all-grain batch and we used 2 satchets of US-05 (rehydrated). We also have about a 3" thick layer of trub at the bottom. We've tried rousing the cake and it looks like it's fermenting (dozens or tidy "bubble rafts" on the top of the beer that I've come to associate with fermentation).

At this point we're just going to dry hop, cold crash and bottle next week and be done with it, but do you think we should keep waiting? Maybe a solution without adding more yeast? The wort itself tastes great, just a little too sweet. (we drink the wort we use for gravity readings)

 

[peterj]

What was your recipe and mash temp (if all grain)? You're using a hydrometer not a refractometer right? Were there any temperature drops during fermentation?

If this was extract, that might be all you're going to get. Extract usually has a fair amount of unfermentable sugars in it. Next time I would try adding a good portion of simple sugar (corn sugar or table sugar) to your wort in place of some extract.

EDIT: I forgot to say that I would probably bump the temperature up to 22-23C for a while to see if you can eek out a point or two more.

EDIT #2: I'm dumb, just saw you said it was all grain in the post! Disregard all that extract talk! Sorry. What was your mash temp and grain bill?

 

[Paradigm]

Grain Bill:
9.3 lbs 2-row
10 oz 40L Crystal Malt
6 oz Carapils Malt
2 lbs Corn Sugar.

We mashed at 155F for an hour and sparged with 170F water. We added tbe Corn Sugar at the end of the boil.

 

[agrazela]

Do you trust your thermometer? Could you have mashed higher than you think?

Did you get a mash pH? Could that have been a bit high? Is the wort darker than you expected?

 

[4D_Glenn]

Corn sugar may have gotten your yeast drunk (too lazy to process the maltose). I suggest adding the corn sugar to the primary after initial fermentation settles down next time. That should get you a nice dry finish.

 

[peterj]

155F is a pretty high mash temp. That's gonna lead to a high fg. I would mash at 150 or lower for an IIPA (I actually just brewed one yesterday and mashed at 150F). I think that was your main problem.

Also what 4D_Glenn said is good advice. With that much sugar it's best to add it dissolved in a little water just after high krausen so the yeast don't lose the ability to ferment maltose.

I would heat it up a bit and maybe repitch an active starter of yeast or transfer onto a fresh yeast cake. That may get you a few more points.
If all else fails and your very unhappy with the sweetness you could try pitching more attenuative yeast like a lager yeast or even a saison yeast. They might contribute a little flavor though, and the saison yeast might dry it out too much.