Is my Imperial Sweet Stout fermentation stuck? The million dollar question

[HopHead73]

Imperial Sweet Stout
5.75gallons in fermentor
OG: 1.091

Mash @ 157degrees:
15lbs 12oz - Pale Ale
1lb 2oz - Caramel 40L
1lb 2oz - Chocolate
9oz - Black Malt

Boil:
1lb 2oz - Lactose Milk Sugar (15mins)
110grams - Unsweetened Cocoa Powder (15mins)

Pitched 1.25L starter with 3smack packs of Wyeast 1318 London Ale III
Aerated with pure O2. Dissolved O2 reading around 11ppm before pitching.

Started fermentation at 66degrees. Raised temp 1degree each day until sitting at 72-73.

After a week took a reading and it was at 1.038.
Two week mark, when adding cocoa nibs and vanilla beans, reading is at 1.034.
Sample is a little on the sweet side obviously.

Beersmith estimates a final gravity of 1.025.

I'm probably nitpicking here, but who thinks the yeast have enough life to get those final 9 points?
I gave the SS Brewbucket a good heavy swirl to try to rouse the yeast.

But, I just want to pick everyone's brains to see what you all think.
Just keep rousing the yeast for the next week and see where its at?

 

[GoeHaarden]

You have to remember that there are many variables that go into where the final gravity ends. Beersmith does a decent job of getting close, but in no way can it account for everything going on in your brew that effects FG. You can use it as a guide, but don't get hung up on the number.

As for your brew. It's only 2 weeks old so I would give it 2 more weeks and see where it lands. I bet it'll chew up some more points by then, but 1.034 is not terribly high for a big beer.

Cheers!

 

[Oldskewl]

I think the yeast may just be finished. With that high of a mash temp and 1lb 2oz of lactose that sounds like a realistic FG. I just brewed a porter with a 158 mash temp and only 4oz of lactose along with 1cup malto-dextrine. I did a 1.5L starter of WY 1028, ramped temps from 66 to 70F. I ended at 1.027FG.

 

[isomerization]

Yes, looks like beersmith didn’t factor in Lactose (9-10 points of gravity) as unfermentable? Factoring that in, attenuation seems appropriate for 1318.

 

[HopHead73]

Ugh yeah that would be what we call at work a "user error".
Forgot to check the "not fermentable" option box on the Lactose addition.

Checked it off and estimated FG went up to 1.033.

Just took another reading and its a 1.032.
Tastes great so probably keg it this weekend.

 

[Calder]

I don't think it is going anywhere. You have roughly 70 + points of unfermentables with the Lactose, Crystal, Choc, and Black malts, so that is a gravity 1.014+ all on it's own. Taking that from the OG and FG readings gives you (1.078 to 1.020) roughly 75% attenuation. Add to that a mash of 157 which should put your attenuation on he lower side, I think you did well to get down to 1.034.

None of the numbers I have used are accurate; just estimates to try and understand if your FG is in the expected range.

To see if BeerSmith accounted for the lactose as non-fermentable, you can change it to (1) Sugar and (2) Liquid extract to get the same OG, and see if either make any difference in the estimated FG. Would be interested in what the result is (I only have a really old version of BeerSmith, which doesn't differentiate any simple sugars.

 

[bracconiere]

Ugh yeah that would be what we call at work a "user error".
Forgot to check the "not fermentable" option box on the Lactose addition.

Checked it off and estimated FG went up to 1.033.

Just took another reading and its a 1.032.
Tastes great so probably keg it this weekend.

damn, and i was all excited about another, 'stuck fermentation' thread.....solved before i got here! sounds like a calorie bomb, be sure to post back with results after kegging, and pouring!

 

[HopHead73]

ChocolateRain

• HopHead73
• Apr 1, 2019

This came out perfect.
Lactose and lower CO2 level makes it super soft and smooth.
Loaded with deep chocolate layers throughout.
Definitely keeping this one in rotation.
Its a great base too for variants like coffee or peanut butter.

 

[bracconiere]

That's a pretty glass of beer there....