My First Lager - When to Start Diacetyl Rest?
 

I brewed my first lager (a simple marzen) 8 days ago. I have read about the diacetyl rest and how to do it. My question is when do I need to start it? Right now I still have a very active fermentation with a nice krausen but I am nearing the point where I need to start the rest (at least according to the instructions; it suggest 7-10 days after brewing).

Do I need to wait for the krausen to fall, or do I need to start the rest soon? Thanks!

Ideally you would do the diacetyl rest when fermentation is about 75% complete (using hydrometer, compare OG to anticipated FG). I'm not that anal though and just give mine a flat 10 days fermenting (remember that lagers usually take much longer to ferment than ales). Then raise to room temp (66-72) for a few days for the diacetyl rest. Then I transfer to secondary and drop the temp 5 degrees per day until I'm at lagering temp... I leave it at lagering temp 35-42 days.

Thanks for the information! Just waiting for 10 days, or for fermentation to all but stop, was what I was thinking, but I did not want to ruin the beer. It is good to hear that I was on the right path.

When you raise the temperature do you do it all at once or gradually? Right now my fermenter temperature reads 52-53.

I just let it raise naturally. I just take it out of the fermentation chamber and set it in a room that is at 66-72. I don't worry about raising it gradually.

10 Days sounds like a fine rule of thumb if you aren't keen on taking a lot of samples.

Also, I'm no lager expert, but I believe that if you do a proper diacytl rest, then you don't necessarily need to do the "slow crash" (couple of degrees a day). You can just cold crash straight down to lagering temps. The slow crash was used to not shock the yeast because the beers were traditionally lagered for a while, then warmed up and krausened to remove diacytl. If you've done a proper d-rest at the end of primary, you have no more need for the yeast (assuming you are kegging) and can crash them down to 32F as quick as you like.

Caveat: that's some Internet learnin' I dun, I'm not an expert.

I just looked at mine(i have glass) to see when it was tapering (about a week)i then raised it to room temp about 68 for 2 days then racked and lagered 15 degrees lower than its ferm temp for 3 weeks,worked out good except i used the temp difference for priming which had me use less which was a mistake. Now i think i have undercarbed lagers, so just use your normal amount of priming sugar and dont pay attention to those temp differences on brewing calcs.Im going on week 3 of priming and going to wait one more to check on carbonation.I then may reopen and add priming sugar-theres no way im drinking a flat lager. I just hope opening them at that point warm wont cause them to gush,if they do ill just leave them i guess.Probably a few more weeks then just refrigerate them.


Actually after i wrote this i kwick chilled one of my lagers at about 3 weeks, i poured it into a SS lager glass with etching and it is carbed and a beautiful lager good head and foamy lacing clear crisp and super tatstey! sucess one of my best so far and my first lager,definatly may post the recipe. I guess i was wrong about the temp carbonation factor.Another impatient noob error on my first lager.
I guess i should know better than thinking how sweet a 1.01 lager was after a week or two of bottle conditioning, guess i was paranoid it wouldnt carb up with such a low priming rate.Time,and time again...

Interesting theory... seems plausible... I would be curious to read more. Got some links to share?

Thanks for all the info guys. I raised the temperature in my cooler to 70 for ~40 hours. Then I transfered to a secondary. It has been in the cooler, set at 40, for a week now. I plan on leaving in there for at least two more weeks before kegging.

You don't have to let it sit in secondary at 40 degrees. I'd probably keg it and lower the temperature if you can. I like to lager at 34 degrees, for a longer period of time. I think it makes a much smoother lager than a lager kept at 40 degrees.

Not being a math wizz would I be correct in calculating a diacetyl trigger at 1.030 for an OG of 1.060 and expected FG of 1.020?