Time for a diacetyl rest?

Brewing my first lager. A Vienna using Wyeast 2206. Starting gravity at 1.064 fermenting 9 days at 49F, just took a reading at 1.024. I am hoping for final gravity of 1.015-1.016. Is this a good time to start the rest? Thanks in advance for any help.

I would recommend doing it soon. The typical recommendation is to do a D-rest when fermentation is about 75% complete.

+1 - sounds like now's the time, if a d-rest is necessary.

Did you taste the sample? Could you detect diacetyl? In a Bock I brewed recently, with pretty similar numbers, I tried a sample while the SG was in the mid 20's, and got a mouthfull of butter with a wierd, almost oily mouthfeel. Gave it a couple days d-rest right then and there, and the end result was a nice, diacetly-free bock.

That said, if you tasted the sample and didn't detect any diacetyl, you may not even need a d-rest.

stratslinger said:

+1 - sounds like now's the time, if a d-rest is necessary.

Did you taste the sample? Could you detect diacetyl? In a Bock I brewed recently, with pretty similar numbers, I tried a sample while the SG was in the mid 20's, and got a mouthfull of butter with a wierd, almost oily mouthfeel. Gave it a couple days d-rest right then and there, and the end result was a nice, diacetly-free bock.

That said, if you tasted the sample and didn't detect any diacetyl, you may not even need a d-rest.

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I can taste it. I pitched plenty of yeast but pitched at a little higher temp than I wanted to.

Yes now is the time.

I'm going through the same process with my first lager at about 6 days fermenting. How much airlock activity do you have? Mine is a lower gravity one 1.040 OG and target FG is 1.010. I used one pack Wyeast Bohemian yeast which took 2 days to get started, so in reality, I've only seen activity since last Friday. Is it usually time to do a D-rest when the Krausen totally falls? Or is it usually before? I'm still getting about 20 bubbles per min. When would you guess it would be ready to do a D-rest? Thanks

I took another reading. Lost another .002. I will go ahead and start the rest... it tastes like Land O' Lakes brewed it right now (I am pretty sensitive to diacetyl though). Thanks for the responses.

Losman26.. I am getting a bubbles every 8 seconds and my Krausen is about 25% of what it was at peak. I used one pack in a 650 ml starter (1/2 cup DME) but pitched about 10 degrees higher than my fermentation temp. I later pitched a second pack when the wort had fallen to 48 degrees .. paranoia or useful??? It took about 18 hours for air lock activity to start.

losman26 - don't try to judge anything based on bubbles or krausen. Some krausens don't drop, others never form (at least, not significantly), and bubbling is inexact at absolute best (completely inconclusive at worst).

Take a gravity reading. If you're expecting a total 30 point drop in gravity, then once you've dropped 22.5 points or so it's about time for a d-rest. So, once you hit right around a 1.018 or 1.017 gravity, it's time.

just out of curiosity, if you had to put a guess on home may days you waited to to the D-rest, what would it be?

Stop thinking like that, man!

Seriously, time, bubbles, krausen - none of them are going to tell you anything concrete. Bust out your hydrometer and test, it's the only way you're going to know.

There's just too many variables at play:
- Different OG's will lead to different fermentation profiles
- Different yeast will lead to different fermentation profiles
- Different temperatures will lead to different fermentation profiles
- Different grain bills, mash temps, extracts, etc will all lead to different fermentation profiles

If you're fermenting it cool like lager yeast is supposed to, keep in mind that a lager _tends_ to ferment slower than an ale. If you absolutely HAVE to put a timeframe on it, then take a look at when you typically start checking for final gravity on an ale. That's as good a time as any for a spot check on your lager. Still too high? Come back in a few more days and check again. Rinse and repeat.

If I was forced at gunpoint to give a guestimate on how long it might take for a typical lager (1.050-1.070 for me) to get to 1.024-1.020 at 50 degrees with an active starter, I'd say 7-10 days or thereabouts.

You want to try to do the diacetyl rest when the yeast is still active, but slowing down in order to encourage them to stay active. A good time is when you are 75% of the way to FG, but I don't take daily SG readings. I wait until the most active signs of fermentation slow down, then take the SG. If it's in the ballpark, I do the diacetyl rest.

losman26 said:

just out of curiosity, if you had to put a guess on home may days you waited to to the D-rest, what would it be?

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It can vary considerably by yeast strain and temperature. If I were using W-34/70 (Wyeast 2124) at 50 degrees it could be five days. If the same strain is used at 45 degrees it will be a few days longer. I am just using S-189 for the first time and I started the d-rest at 1.022 on a 1.054 lager on day 15 fermenting at 50 degrees. There has been a strong krausen for the entire fermentation.

So once again I must observe that your calendar is not useful for fermenting lagers in any way, shape or form (though it is of course useful for keeping track of the lagering [cold storage] period). Your hydrometer is what you rely on. Having said that, as you become familiar with a particular strain, you can see when it's time for a d-rest--usually when the krausen starts to thin out noticeably or fall.