Diacetyl Rest Method?

[John Sand]

I have a small batch fermenting at 56 right now. Rather than warm it in the fermenter, I plan to carb it with sugar in the keg and warm it there.
Thoughts, opinions and especially experience?

[Beer-lord]

I did this once in a 2.5 gallon keg. I just pretended it was a big bottle and used the carb calculator. I think it was a Cascadian Dark Ale and it turned out fine. It did take a little while for the sediment in the bottom to clear out ( the first 6-8 pours or so). I brought it to an event in a cooler with ice and just used CO2 to push the beer out. Took about 2 weeks to be ready.

[John Sand]

Thanks. I have hardware to draw from the top. Maybe I'll use that.

[mashani]

Yes, but it will likely take longer. The diacetyl (also acetalahyde) uptake is due to the presence of the yeast, and the more yeast that is present and the more active the yeast is the faster it will happen. (warm temps don't do something magic to make the yeast decide to "uptake" it during a rest, it just makes it happen faster, it will still happen if you leave it cool, as long as it's not so cool the yeast become inactive, it will just take much longer). People want it done in 2 days, so big yeast cake and warm temps = win.

If you have a huge amount then it might be problematic. If you take it off the yeast cake and there is a lot of diacetyl (like say some English yeast can make) then even bottle conditioned with yeast present the diacetyl can persist for a good long time if not forever, because there wasn't enough yeast present and active to do the job.