Planning for my Diacetyl Rest

I've got two lagers going in my fermentation chamber right now. This is my first attempt at a lager and I'm planning out when to do my rest. I've read the threads, but I would like some specific advice if you guys can offer it.

I've got 2 five gallon batches that went into the fermenters on Sunday. Beer 1 is a 1.043 gravity shiner bock extract clone using WLP833. Beer 2 is a 1.056 gravity all grain mexican lager (151 F mash) using WLP940.

I pitched 2 liter starters for both at 65 F and when i got first signs of activity (the next morning) I dropped chamber temps to 50 F.

This morning I checked gravities and temps again. Beer 1 is at 51.9 F and 1.022 (after correction to 70). Beer 2 is at 51.2 F and 1.033 (after correction to 70).

Now for the question:

I've read that you should start to move to your rest temps at about 2/3 of a complete fermentation, but I've read that most people hit that point at about 10-12 days. It looks like I'm moving a little quickly and will hit 2/3 earlier than that. Should I pull them at 2/3 even if it's only a week at 50, or is that premature? Based on these yeast, can you give me an estimate of what gravity you would head towards a rest? Finally, from what I've read, if beer 1 hits 2/3 before beer 2 I can leave it at rest temps longer and bring them both down to lager temps together, correct?

I know I'm over-analyzing here, but as a scientist myself, I like to have a complete understanding of the process.

Thanks for the help! Sorry for the barrage of data, hehe.

I normally do my diacetyl rest at about day 5-7, depending on the OG of the beer. You want to do it when you're about 75% of the way to FG, when the yeast is still active but slowing down. You want active yeast to digest the diacetyl, but you don't want the flavor impact of fermenting lager yeast too warm.

Incidentally, next time instead of pitching at 65 and holding there and lowering the temperature, try pitching at 48 degrees or so, and raising it up to 50. You may avoid any excess diacetyl creation in the first place by cold pitching, and the yeast love being warmed but not cooled so the flavor from pitching cold tends to be "cleaner" in my experiences.

Thanks

I hesitated to pitch at 48, since this was my first lager. Beersmith said a 2 liter starter was sufficient, but from what I was reading other places it seemed a little small, so I wanted to give the yeast an easier time.

So does it matter if 75% comes really quickly?

jinjosavior said:

Thanks

I hesitated to pitch at 48, since this was my first lager. Beersmith said a 2 liter starter was sufficient, but from what I was reading other places it seemed a little small, so I wanted to give the yeast an easier time.

So does it matter if 75% comes really quickly?

Click to expand...

+1 on what Yooper said about pitching cool. The warm pitch method is done to compensate for under pitching. Like Madam Yooper, I don't consider it a good brewing practice.

I usually check my lagers in 7-9 days. By then, because of a healthy pitch rate, they're normally 75-80% of the way to expected FG, so I'll bring it up to 62-64 for the d-rest.