When to do diacetyl rest?

[MikeB]

I just brewed my first lager 12 days ago. It started slow, but has since been fermenting steadily for eight or so days. I plan on raising the temp 5-8 deg (from 50 deg) to do a diacetyl rest and wondered when I should do this I'm getting a bubble from the carboy about every 10-12 seconds. Do I wait until just before I transfer it to my lagering vessel (corny)

Cheers,
Mike

[BrewTa2]

Now is a good time to raise the temp, but go higher, 65-68F. Click HERE for more information on diacetyl.

[dmtaylor]

+1, what he said.

The unofficial rule of thumb is to do the diacetyl rest when fermentation is about 2/3 done. So, if you have a beer at an OG of 1.050 that you expect to finish at 1.013, you'd want to do the diacetyl rest when the gravity reaches (50-13)/3 + 13 = 25 gravity points = 1.025. Make sense? Otherwise, if you don't want to dick around with math or taking gravity readings (I don't always), just give it about 8-10 days fermentation, then raise it up to about 60 F for about 3 days, by then your fermentation might be done, or if not, you can bring 'er back down to the 50s again to finish up before lagering. It may look like rocket science but it really doesn't need to be. You can wing it and it'll turn out fine.

[MikeB]

Thanks for the info. I thought you'd want to have a fairly active fermentation while doing the rest. It's at 60 and climbing.