Fixing diacetyl

Make a big active starter with a neutral ale yeast and pitch it once you bring the beer up to around 70F. That's your best bet. Active yeast will metabolize diacetyl. If you can, purge the headspace when pitching the starter to avoid any oxidation that might happen so that you can lager the beer afterwards.

 

Should be just fine. If you get additional fermentation and a little more attenuation, I think that'll be the least of your worries.

 

FWIW, make sure to a diacetyl rest BEFORE your fermentation is completely finished (usually 2/3rds the way through is suggested) and this won't happen in the future.

 

I don't believe in diacetyl rests, but I do believe in pitching plenty of active and healthy yeast. Pitching new active yeast should help here. ( though I have never tried it or had to do it, in my over 1200 batches).

 

I have never brewed with Fermentis 34/70 but I have brewed many, many times with Wyeast 2124 which is reportedly the Weihenstephan 34/70 strain. I have never conducted a diacetyl rest and I have never perceived diacetyl in any of the resulting beers (and I am very sensitive to diacetyl). My 'take away' here is that if you conduct a healthy fermentation with this yeast strain a diacetyl rest is not needed.

Cheers!

P.S. Jim (@premierpro), have you ever experienced diacetyl in your beers where you utilized 34/70?

 

Is this beer still in primary? If so, I'd warm it up to D-Rest temps for a few more days and see.

If that doesn't do the trick, then pitch more yeast as others mentioned.

 

I wouldn't seal it after pitching an active starter.

 

Leave it warm for 3 weeks. Diacetyl will magically disappear.

I have diacetyl in a W-3470 lager right now. I ain't worried at all, not at all. It's pretty slight anyway. And it's still in primary, which is nice.

 

I would "airlock" it in some way that excess pressure can escape, unless you're sure that the amount of fermentables you are adding won't make too much.

 

That will certainly be safe from a keg pressure standpoint. I don't know if the yeast will like it (the pressure) from a diacetyl eating standpoint, but it should make for an interesting experiment. Maybe @TheBeerery has some insight there...I think he spunds before fermentation is complete.

 

I have rescued at least three beers from diacetyl as follows:

Warm the beer. Make a small starter of neutral dry yeast. I have done this with notty, us 05, and even lager yeast 34/70. It really shouldn't matter. You probably could use t59 and it wouldn't matter. When the starter shows signs of active fermentation pitch into your keg or secondary. Forget about the beer for 2-4 weeks. Drink.

 

What ever you do, don't just dump the keg. I had a horrible diacetyl problem in a batch of Czech Pils, but I did not need the keg so it just sat in a hot garage all summer long (probably 5-6 months). Before I dumped it, I gave it a try and the diacetyl was gone, ended up finishing the keg, not the world's best beer, but not worth dumping either.

TL;DR don't dump the keg unless you need it for another beer. Just let it ride at room temperature and see what happens. Or pitch more yeast