Diacetyl Rest For Lagers

[Snow]

Guys, can anyone offer me advice on when is the best time to give a lager a diacetyl rest? I have a bock in the fridge with White Labs Oktoberfest yeast that's been sitting at 9C for about 11 days. It has been bubbling slowly but regularly the whole time. I racked it to secondary yesterday and the SG has dropped from 1.051 to 1.020. It is now bubbling at the same rate as it was in primary. Should I leave it at 9C until fermentation has completed fully or should I bring it up for a diacetyl rest now?

Is there a formula I should use for SG levels to guide me?

Cheers - Snow

 

[Snow]

Oh, come on.... doesn't anybody have an answer to this??

 

[deebee]

I've been leaving this one to someone with more know-how, but I got some good info from John Palmer and then basically just brought the temp up to about 20C fro 36 hours before lagering.

 

[PostModern]

John Palmer reckons:

To remove any diacetyl that may be present after primary fermentation, a diacetyl rest may be used. This rest at the end of primary fermentation consists of raising the temperature of the beer to 55-60 F for 24 - 48 hours before cooling it down for the lagering period. This makes the yeast more active and allows them to eat up the diacetyl before downshifting into lagering mode. Some yeast strains produce less diacetyl than others; a diacetyl rest is needed only if the pitching or fermentation conditions warrant it.

I haven't brewed any lagers yet, but plan to put on a Bock this week, now that temps are nice and cool. I was kinda researching this myself

 

[Barry]

Good Day
I went to a talk by Chris White of Whitelabs a year or so ago and he said that the diacetyl rest is best when the SG is 1.020 because there is more suspended yeast to "eat up" the diacetyl. The beer is then cooled down again to finish fermenting. The need to have the rest might depend on the type of lager yeast used, some are noted diacetyl producers and some are not.

 

[Snow]

Thanks, Barry. As it turns out, The SG was exactly 1.020 when I racked it, so it looks like I was on the money! I'll give it 3 days at 18C then pop it back in the fridge for lagering.

- Cheers - Snow.