Reasonable final gravity?

[ndrice]

I just brewed a really big Russian Imperial Stout and I'm starting to have some concerns about my fermentation.

These are the recipe specifics:

14 lb. Golden Promise
3.0 lb. brown malt
2.0 lb. amber malt
2.0 lb. Piloncillo sugar
0.75 lb. black malt
4 oz. Challenger hops (120 mins)
4 oz. East Kent Goldings hops (30 mins)
WLP 0013 (London Ale) yeast

Step by Step
Mash at 158 °F (70 °C) for 120 minutes at 1.32 qt./lb. Boil for 120 minutes. Half of black malt is added to the boil (in a hop bag). Ferment at 65 °F (18 °C).

I made a 3L starter of the London ale yeast using a stir plate and shook the hell out of the carboy when I pitched (no O2 system for me).

My OG was 1.116 The recipe says the FG should be 1.019, but I can't believe this will get that low given the high mash temp and large amount of dark grain. All of my recipe calculators say this should finish out at around 1.030-1.033 which seems more reasonable.

Given the mash temps, boil times and yeast selection, what sounds like a reasonable final gravity to expect?

After 3 days, the beer is down to 1.051, but seems to be slowing down considerably. Time to go into yeast babysitting mode, I guess.

 

[EarlyAmateurZymurgist]

You could always pitch Saccharomyces diastaticus (S. diastaticus). S. diastaticus is kind of like Saccharomyces cerevisiae without limits. It can even break down starch and dextrins; hence, the "diastaticus" part of it's name. Oh wait, what was I thinking? That would be an incredibly stupid thing to do because S. diastaticus is a bugger to eradicate from brewery.

 

[karzak]

You're correct that your FG will be higher than 1.019 due to the high mash temp.

I brewed a large beer recently (OG 1.090) that I mashed at 162F (!) in order to pitch brett after primary with plenty of sugars remaining. Using WLP 001 it came out around 1.029. I would expect yours to finish up in that range and be fine flavor-wise. Maybe give the yeast a stir and raise the temp to around 72F after 10-14 days if you are worried.

 

[Calder]

I don't think you will get down to 1.019 because the yeast will give up due to high alcohol. That would be a 13% beer.

Remember you have 2 lbs of sugar in there that will help bring it lower than the calculators say; probably by about 5 to 6 points.