Add more yeast or not?

[PhilM]

Have an imperial stout in second fv for a month or so now and am starting to think about bottling. No activity for the last 3 weeks in the air lock. Getting worried about carbonation. Should I add more yeast when bottling?
Probably good to know that it’s about 9%.
(OG 97, when transferring to 2nd FV 30)

 

[divrack]

Why do you want to add yeast? You want to be sure it's finished, yes, but i don't think the yeast will struggle to carbonate it. That said if it's been bubbling since you added it to secondary it means it's gota lower fg so it could be around ten percent easily where some yeast can start to struggle.
That said I've never had real problems getting yeast to carbonate strong Beers unless they are much older but perhaps I'm lucky. You could add some high alcohol tolerant yeast if you want with a similar attenuation.
Really you want to measure it now and see what it's at.

 

[terrym]

What was the original yeast? Look up the manufacturers data sheet and compare your 9% alcohol & 69% attenuation with the expected performance. That will give you an idea of whether its still good to go or whether its gone as far as it can.

 

[PhilM]

It’s Nottingham yeast so it should be ok for higher abv. Measure it know and it’s basically not changed. Maybe 29 instead of 30.
Had an idea and have taken out a little more into a small plastic bottle and added some sugar. If the yeast is still active I should notice it in the bottle with a few days ie the bottle should firm up.

 

[PhilM]

Thinking about the last measurement. 30 seems a bit high and it should finish at about 22 according to my recipe. Could this be a sign that the yeast has died off?

 

[divrack]

Missed your post.. I doubt the yeast is dead, it's just given up on its dinner. Given the high strength and lots of harder to process sugar I don't think 29 is out of the ball park. You could add some more attenuating yeast or some enzyme if you really want but I think you'd be better just bottling what you have.
Leave it a couple days and retest. If it's still in the same place prime and bottle and leave for a few weeks and you should have a great beer.

 

[PhilM]

When you say “attenuating yeast” what would you recommend? I was of the impression that Nottingham was quite high.

 

[terrym]

Danstar say their Nottingham yeast will go up to 14% ABV and will achieve 'high' attenuation, which Brewers Friend interpret at 77%. So even with a bit of wiggle room on these figures you should have expected your brew to go a bit further. Perhaps its those harder-to-process sugars @divrack mentioned. If I were you I would now have a taster. If its too sweet for you then you might have to resort to a Plan B. If it's not, get it bottled, but put one in PET as an indicator in case it does decide to take off again.

 

[divrack]

When you say “attenuating yeast” what would you recommend? I was of the impression that Nottingham was quite high.

Yes it's quite good. As I say I wouldn't do those suggestions. You'd have to go with a diastaticus or Brett strain probably. Or use an enzyme but that might go too low. Honestly high twenties for an imp stout is fine. Some people go to a lot of trouble getting them to stop that high.

 

[PhilM]

Ok, thanks for all the help. Waiting on my PET-bottle test. Hopefully that will show if the yeast is active. Will let you know the result regardless.

 

[PhilM]

The PET test seems to have worked. Bottled this evening so we’ll see in a couple of weeks