Is five days too long for a Lager D-rest?

Brewing Processes
1

I’m getting ready to do my first lager.  Due to my schedule, I have to leave for a five day trip on day 10 of fermentation.  I think five days of a D rest at 65 or 68 is fine (from what I’ve read), just wanted to check and make sure. Here’s my plan. If anyone has any advice, please let me know as well.

Make a large starter calculated for lager.  Wlp830.
60 minute mash single infusion 148°.
90 minute boil.
Chill to around 46, oxygenate, Pitch large starter. Ferment for 10 days at 48 Degrees.
Before going out of town (day10) turn the temperature up to 68 for the five days I’m gone.
Arrive back from trip and cold crash to mid 30s for About a week, then transfer to a keg and lager at 32° for 4 to 6 weeks.
Tap and hopefully enjoy.

Any opinions? Thanks.

2

Fermenting at 50°F, my lagers hit FG in under 7 days, so if doing a D rest, it would be around day 4.  Watch your progress carefully, this may be a non issue.  As with any beer, we don’t set a schedule for the yeast to follow, they set the schedule for us.  If it does play out as you’re expecting, it  will be no problem either.  And with a high enough pitching rate and your low pitching temperature, a D rest may be unnecessary.  Again, let the beer lead.

3

That is a long time, and the beer might still have a long way to go at 10 d. Consider fermenting at 48 for 15 days and then warm when you get home.  68 seems high, you could go quite a bit lower, 60F say.  At 48, you will have created very little diacetyl to need to reduce in the first place.    Alternatively, don’t use a D rest!  I am using the same strain as you, and have quit using D-rests*.  I ferment 12-17d  at 48, and lower temp 2 deg each day until 36 or colder.  Then hold for a week and rack and lager for 8-10 weeks.  This is a traditional method, but comes at the cost of needing a long lagering time.  The D rest enables quick turnaround of lagers  Try both methods, see which you prefer.

*I have not tried this on other lager strains.

4

This is one of those questions where you ask 10 brewers and get 10 completely different answers.

Here’s mine:

A diacetyl rest is only needed if you smell or taste diacetyl in a sample.  If not, then it’s optional and you might even be better off keeping it cool – less fuss, less hassle, zero stress on the yeast.

On the other hand, it technically never really hurts to do a diacetyl rest at the right time, whether you have any diacetyl concerns, or just want to speed up the fermentation, or whatever else.  Just be sure to implement the D rest near the end of the primary fermentation.  I aim for when the gravity points are half what they started with.  So for instance with OG of 1.052, I aim to start the D rest at 52 / 2 = 26 or 1.026… IF I am going to do a D rest.

Furthermore, when diacetyl IS detected, at any amount however slight or strong, I believe nobody really does a D rest long enough.  Three days?  Four days?  Why not one week?!  Three weeks?!  Four weeks?!  The reason I say this is that I KNOW from experience that diacetyl doesn’t just disappear overnight in 1, 2, 3, 4 days like magic.  No, no it doesn’t.  After I bottle a batch, it has been very common, with many different yeast strains by the way, for diacetyl to show up as soon as the bottles are carbonated, which then tends to last for about three WEEKS… and then suddenly at some point during the third week, it magically disappears.  Mine are conditioned at cool basement temperatures of about 55-65 F by the way.  So, if you want to try a D rest for 5 days instead of just 3 or 4?  Don’t worry about it!  This is the least of your worries on this earth!!!

Some other odd insights: I am currently fermenting a Kolsch and a pilsner side by side at 51 F.  And while neither one smelled or tasted like diacetyl at all at the 1.026 halfway point, I had to leave town for 4 days, so I had a decision to make.  In this case, I figured for the Kolsch since it is already probably a bit too cold for that particular yeast (K-97), I kicked up the temperature to about 55 F for 4 days while I was gone, not so much as a D rest but more as a kindness rest(!).  Meanwhile, I left the pilsner alone (S-189) at 51 F as I know it will keep on chugging just fine.  Upon my return, as I expected, the Kolsch is almost at final gravity, maybe within 1-3 gravity points, while the pilsner (with S-189) is moving along much more slowly but steadily from what I can tell (I have not taken a second sample quite yet).

In your specific case, bottom line, I would say this:  Smell and maybe taste your beer.  Diacetyl?  If not, leave it alone.  If yes, then go ahead with the D rest, for AS LONG AS YOU LIKE.  Five days?  Five weeks?  Well maybe 5 weeks is a little excessive.  But, yes, yes, I am serious.

Cheers and enjoy.

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[emoji106]

6

I recently used the WLP830 in a German Pilsner and I still had very regular activity in the air lock on day 10.  I checked my gravity every couple days and it was still dropping until it finally reached FG on day 12.  My fermentation temperature was 50°F.  Now, I did a 4-day D-rest at 60°F only as a force of habit when brewing with a Pilsner Malt.  So, as was stated by one of the other brewers, the yeast will dictate its own progress.

Personally, I would allow it to stay at fermentation temperature until you return from your trip, then check it and make a decision on moving forward.

BTW - this German Pilsner turned out to be one of the best beers I’ve ever made.  I really like the WLP830!

7

Malt type has no bearing at all on diacetyl. Diacetyl is a fermentation product made by yeast, and if they are going to, they will produce it in any wort.  Note that it is sometimes regarded as a characteristic feature of British ales.  WLP830 is, however, a very low diacetyl producer.

8

I would check specific gravity the evening before you leave.  If SG has passed the halfway point, then I’d bump it up, otherwise I’d leave it cool and check SG upon your return.

9

Just like there is no specific temp for a d rest, there is also no specific time.  Dave’s advice is good.

10

Thanks, Robert, for this information.  I knew diacetyl is a byproduct of yeast during fermentation.  However, for some reason, which I can no longer remember, (happens when we get old) I was under the impression the D-Rest was mandatory with Pilsner Malt.  You see, we never stop learning!  Thanks!

11

Thanks everyone, making the starter tomorrow for the Brewday this weekend.  We’ll see how it goes👍🏽

12

Well, I just checked gravity seven days in when the bubbling is tapering off and I’m already at 1.010.:expressionless:. Hopefully I’m not too far in to do a D rest so I am raising the temperature slowly to 65.

13

I’m not trying to spend your brew dollars but consider purchasing a Tilt hydrometer. I have been using mine for a while now and I am completely happy with how convenient it is to check the active fermentation daily. This would definitely help avoid missing your D rest!! I think they cost approximately $100

14

Just tapped it, and very very happy with it.  Thanks for all your help!

15

Just asking.  Are you possibly confusing diacetyl with DMS, KellerBrauer?  Pilsner malt has more propensity to produce DMS because it contains more of the pre-cursor that produces it.  It boils off in a good rolling uncovered boil.  Not accusing you of not knowing the difference, just looking to clarify that you haven’t confused the two.

16

I do that. I have to look them up to keep them straight.

17

Ya know, that’s a very good possibility goose.  And, in fact, now that you mention it, I was doing a good strong rolling boil on all my worts until I read a post a while back by Mr. Brungard (SP?) where he stated it wasn’t necessary.  So, I cut back on my boil vigor and haven’t noticed any change in my finished beers.  However, I was still doing a d-rest on my brews where I used a Pilsner malt.  Now I’ve learned it’s not necessary either.  Thanks for asking!  It’s nice to reactivate some dead brain cells now and again!  :wink:

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Glad to help you reactivate them!  I have to do that here from time to time as well!  :smiley:

I also read Martin’s article in Zymurgy and have cut my boil times from 90 minutes to 60 minutes in all my beers except for my Wee Heavy (120 minutes) and my ESB (90 minutes).  Both seem to benefit from the longer boil times and seems to improve the character of the beers after fermentation, at least on my palate.  I have also reduced the vigor of the boil as well and it also conserves propane.