Beer Forum

Brewed a Mexican Lager on March 20th. Pitched a very large starter of WLP940 Mexican Lager yeast. OG was 1.055. Started it at 48F, two days later raised it to 50F, four days later raised to 52F. Just six days later it stopped bubbling. Checked gravity. It's at 1.010 and 5.9% ABV (by my math). This is better attenuation than I was expecting and super fast. I've brewed this beer a few times before and it always took 2-2.5 weeks to finish...not 6 days. Was worried about infection, but the sample I took for gravity smelled and tasted fine.

Question: Should I keep it cold? It's at 54F now. Or raise it for D-rest, then lager? Does D-rest still work if it's done fermenting?

I would.

At this point, you should be able to free-rise it all the way up to 70F with no problems whatsoever. Keep it there for a week.
Any byproducts will be taken up by the yeast and you'll be left with a clean, great tasting beer.
Let us know how it goes-

Even if you are at terminal gravity, the yeast will still uptake the diacetyl unless they are really dormant. I think the only way that you can effectively shut them off like that is to drop the temperature down too cold, maybe 35F or less. The colder it is, the longer the uptake period will be. At 65F or so it happens pretty quick.

Does it taste like diacetyl? If it doesn't taste like it then you are probably in fairly good shape, though a heated diacetyl test is a good thing to do for ensuring that it is gone. If you don't know what that is, I think that 'the google' will find it fairly easily.

In really extreme cases, you can take some yeast up to high krausen in some starter wort and throw that in. That will clean up things that are total D-bombs. It doesn't sound like that is anything you require though.

Sounds like a good strain to work with.

I have been doing a lot of lagers lately (taking advantage of the colder water temps to chill faster) with WY 2206. I have found that when pitching cold (44-45F), that I get zero diacetyl carried through to the final product. This of course requires a large pitch of healthy, active yeast and a cold fermentation temp (46F).

With that being said, as Bdawg and Nate said, you can easily let this rise up to high 60's or so to continue to clean up a bit. After a week at those temps, crash it for lagering.