Restarting a stuck fermentation

3qsmavrod5twfe

Hi all. I am new to the world of homebrewing and I have a story/question for all you gurus.


I am working on a St. Peter's Stout kit, and I encountered the dreaded stuck fermentation - the SG was stuck at about 1.018 for about 4-5 days. I read up a bit about options to try and get it going again and considering there were no temperature spikes (up or down) or infections or anything like that that I could have put down to, I decided (with my exceptionally limited knowledge) the best course of action was to repitch some yeast back in there.


I spoke to the folks in homebrewwest and I asked for a neutral ale yeast figuring that I didn't want to get any "interesting" flavours in there - they gave me a Munton's Gold yeast. I also transferred the partially fermented wort into a secondary to try and get it off the trub - this I might add I did for no other reason other than I felt like I needed to do *something* with it. Also, when I asked the guys about making a starter out of the dried yeast they suggested it wasn't really worth the effort. So I lobbed in the packet of yeast and hoped for the best.


Since that, the fermentation has kicked off again and seems to be plodding along fairly consistently actually. The most surprising thing I have found though is that after about another 12-14 days it is still going! There was vigorous bubbling through the airlock when I repitched the yeast but I'm putting this down to outgassing due to adding a shedload of nucleation points for the gas to form on. Since then it has been a fairly consistent flow of bubbles - now I know this is not an indication of much, but when I did a SG and *ahem* quality test on the batch it had gone down to 1.012 (and still going) and tasted just fine albeit a bit green.


This has been going on for the better part of 2 weeks now - I guess all I am just looking for some reassurance that everything is going to be OK . Seems like it has been rescued from the jaws of defeat, but is there anything I should be worried about here. I know the real test will be drinking the finished product. Any ideas?

Bogwoppit

Just keep testing the gravity until it stops moving.

oblivious

What was the original gravity ? 1.018 is not to bad

You could try rousing the yeast with a sanitized long spoon

3qsmavrod5twfe

The OG was 1.048, so exactly where it was meant to be. At 1.018 you could still taste a fair bit of sweetness in it. The main fear was that if I bottled at that point with a fair bit of residual sugar in it (that is meant to be fermentable - this is a kit) that I'd end up with bombs.

oblivious

Izabella Glamorous Babysitter wrote: »

The OG was 1.048, so exactly where it was meant to be. At 1.018 you could still taste a fair bit of sweetness in it. The main fear was that if I bottled at that point with a fair bit of residual sugar in it (that is meant to be fermentable - this is a kit) that I'd end up with bombs.

Try gently rousing the yeast then

RasTa

1018 is the perfect gravity for a stout unless it's meant to be a dry Irish one.

oblivious

RasTa wrote: »

stout unless it's meant to be a dry Irish one.

That's just a meaning less term made up by the BJCP

RasTa

oblivious wrote: »

That's just a meaning less term made up by the BJCP

I disagree, I don't want a thin 1010 dry finish for a stout.

dukeellington

my general advice is not to stop a ferment just because SG is where you expect to end, if you stuck get it restarted, but in my opinion, you've got to let the yeast run its full course. once it's finished let it age in the bucket until you get the best flavour then bottle. if the sg is lower than you aimed for and you want it less dry or whatever thats something to look at changing yeast for the next batch of the same recipe, not to be worried about on this brew.

3qsmavrod5twfe

Finished up at 1.012 measured 2 days apart.


In summary re-pitching some yeast (dry yeast at that) seems to have done the job in terms of finishing a fermentation, real test is a taste test in a few weeks.

neoanto

Just a note on dry yeast. No need for a yeast starter with them, but make sure you rehydrate the yeast.
Without rehydration I think you can kill off up to 50% of the yeast but pitching them dry.

loyatemu

neoanto wrote: »

Just a note on dry yeast. No need for a yeast starter with them, but make sure you rehydrate the yeast.
Without rehydration I think you can kill off up to 50% of the yeast but pitching them dry.

there's no harm in making a starter, at least you'll know the yeast is alive.

neoanto

Its not needed for dry yeast.
With liquid yeast you cant be sure of the viability of the yeast and thats one of the reasons for the starter.
Dry yeast is much more hardy and so only rehydration is only required.

Also if you're making a starter it will cost more as you will need some DME and a stir plate.

loyatemu

neoanto wrote: »

Its not needed for dry yeast.
With liquid yeast you cant be sure of the viability of the yeast and thats one of the reasons for the starter.
Dry yeast is much more hardy and so only rehydration is only required.

Also if you're making a starter it will cost more as you will need some DME and a stir plate.

OK - I didn't mean a full starter in the liquid-yeast sense, just rehydrating with some sugar or DME to start it working before pitching. Palmer calls this "proofing" the yeast.

neoanto

Ah ok, I thought you meant a full starter.
Yup just as you said, rehydration is grand for dry yeast.