Wee Heavy 5 months conditioning in carboys and still fermenting

[StrathclydeTaff]

I brewed my first high OG - a Wee Heavy - last November. OG 1.080. After several batches of pitched yeast (fermentation kept stalling after very vigorous primary phase with large kraeusen), I managed to get the gravity down to 12Bx, 1.026 after 7 weeks. Transferred into carboys with airlocks and put under the stairs at 20C, where its been for over 5 months.
It is still fermenting, microbubbles are regularly rising in the brew, pressure in positive and the airlocks are burping regularly. Current gravity readings are 10Bx giving ABV of 8%. it tastes ok so I think the activity is the yeast rather than any infection.
My question is how long is activity likely to continue for before I can bottle?

[Kev888]

There can be some residual activity, especially in big or difficult beers, but it should really have reached nominal Final Gravity looong ago. Bubbles and airlock activity aren't a good indicator (other things can cause them) so gravity is the best of your measures to trust.

You need to check if the gravity is no longer falling, say by measuring a week or two apart, if it isn't then there is a chance it is done. The FG is high but then so was the Original Gravity; it seems you have nearly 70% attenuation which isn't out of the question for it being finished - depending on what yeast were used, the pitching rate and how well the wort was aerated.

Also, you mention Bx which suggests you 'may' be using a refractometer; if so then have you compensated its reading for the presence of alcohol and/or compared it against a hydrometer?

[StrathclydeTaff]

Kev
Thanks for your comments which are reassuring as I was worried that I might create bottle bombs.
I've been using a refractometer and the Northern Brewer calibration tool for alcohol effect. My latest reading at end May was the same as that taken in March and the only reason not to bottle was the continued activity in the carboys.

Sounds like I can go-ahead and bottle but some further explanation of what is causing the activity would be appreciated. Is it residual sugars that are being digested very slowly?

thanks

ST

[Kev888]

After this long and with the gravity going nowhere over weeks, it seems safe to say that it has pretty much stopped, the concern (as always) is whether it could potentially start again, which is more of a worry with high FGs. In this case with nearly 70% attenuation and such high OG and alcohol content there isn't necessarily reason to think it has stuck prematurely, that could well be all it will do - though to judge the risk further it could help to know what yeast and mash temperatures were used, in order to get an idea of what would be expected here.

Yes, to a degree the yeast do work away after the fermentation has outwardly subsided. Residual activity on the difficult sugars can tail off quickly but go on very slowly for quite a long time, and they also metabolise other things including some undesirable by-products of the main fermentation (part of the reason for maturing beer). When activity dies down, they change themselves somewhat in preparation for going to sleep (as it were), though as time goes on more die which can release things too - they are more stressed in very high ABV brews such as this one. There will additionally be particles or haze settling out, and there will be a little CO2 dissolved in the beer and perhaps trapped in sediment. So yes, for one reason or another small bubbles can appear for quite a long time. Another key culprit for airlock activity other than from the beer is any changes in temperature (or movement of the fermenter), which can cause the vessel to either suck or blow (or both in a cycle).

There is also the outside possibility of infection/contamination; something else having a go at the residual worty goodness but not producing alcohol in the same way that yeast do. Usually there would be some other signs, such as in flavour, though it might take a while for them to show.

[StrathclydeTaff]

Kev

Thanks for that great insight into conditioning and fermentation of high OG beers. This is my first effort with high OG - my usual brews are normal strength and I've usually bottled about three weeks after pitching when FG has been static and the airlocks show balanced pressure.
This brew is from LME. Conditions under the stairs have been constant during conditioning.

I bottled on Saturday with 2.5oz of priming sugar for the 23 litres. My plastic tester bottle has been expanding slowly with some trub accumulating so I'm getting some secondary fermentation so we'll see how that reacts when I open it in three weeks time.

cheers

ST