Lager Diacetyl rest

When is the optimal time to do a diacetyl rest for a lager. I have done an extract recipe where I did not do a rest at all and did not have any off flavor of diacetyl and done an all grain where I have done a diacetyl rest for the last 2 days of primary fermentation and have had substantial diacetyl flavor. Thoughts? Maybe I have done something else wrong during the process to have left over diacetyl in my beer.

"By the book" you followed a good process for your ag batch. Depending on the yeast strain used, a rest may not be "required", and some may need an extra day or two. What temp did you use for your rest, and how did you lager afterwards?

Ideally, you are supposed to do the D-rest when you have reached 75% of FG. For example, if your OG is 1.05 and your expect FG is 1.01, then 1.05-1.01=1.04; 75% of 4 gravity points = 3; 1.05 - 1.03 = 1.02; So you would do the D-rest at 1.02. 48 hours at 70ish, IDEALLY ramping up from your fermentation temp to 70ish at about 5 degrees/hour, then following the D-Rest, ramping down to lagering temps at about 5 degrees/hour.

When I do lagers, I generally follow those rules, but I'm pretty lax about getting everything perfect, and my lagers turn out great, but ideally, that's what the procedure would be. As a benchmark, 75% FG is generally right about when you start to notice the fermentation slowing down as far as airlock activity.

501irishred said:

"By the book" you followed a good process for your ag batch. Depending on the yeast strain used, a rest may not be "required", and some may need an extra day or two. What temp did you use for your rest, and how did you lager afterwards?

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I used WL Octoberfest yeast and the rest was done at 68F. I know the rest should be at a higher temp but my basement does not get that warm in the summer time and I do not have the equipment to raise the temp. I lagered at 45F for 4 weeks and kegged at 42F for 3 weeks.