Diacetyl Rest

dan_s · January 14, 2012, 3:05pm

Hello Everyone,

I have a question about when to start a diacetyl rest. Eleven days ago I brewed a Maibock with White Labs 833. Brew day went well and I pitched a big yeast starter at 50* that took off quickly and has since settled down. The carboy has been sitting at 50* in our basement fridge since brew day and yesterday’s gravity reading showed 1.030, down from 1.065.

My question is: when should I start raising the temperature for a diacetyl rest? I’ve read that the last third of fermentation is considered to be a good time to start raising the temperature – is this idea based on achieving roughly 2/3 of the expected gravity loss due to fermentation? If I expect to get down to roughly 1.016 or so, I think this would mean starting to raise the temperature at about this time.

Any help would be appreciated!

bothfeet · January 14, 2012, 3:49pm

Others may have a different opinion but i let mine finish, then give it a D rest. I love 833 and that has been my procedure with great results. I think if you move the temp up to soon the yeast will start to throw off some undesired esters ect. I usually give my lagers at least 2 weeks and usually 3 in the primary then transfer for lagering. You know that whole axiom about being patient with your homebrew??? Its multiplied by 10 with lagers.

bothfeet · January 14, 2012, 3:54pm

BTW i should mention that later this afternoon i am transferinng a Munich Helles off a 833 yeast cake and brewing up Ken L’s red lager to pitch on the yeast cake. I brewed the Munich on Christmas eve.

tg · January 14, 2012, 4:38pm

That is the standard teaching. The thought is that most of the esters are produced at the beginning of fermentation during the yeast growth phase. Others report just leaving it at fermentation temperature with good results. Some yeasts are prone to producing more diacetyl. I don’t recall 833 being one of them.[quote=“Dan S”]Hello Everyone,

I have a question about when to start a diacetyl rest. Eleven days ago I brewed a Maibock with White Labs 833. Brew day went well and I pitched a big yeast starter at 50* that took off quickly and has since settled down. The carboy has been sitting at 50* in our basement fridge since brew day and yesterday’s gravity reading showed 1.030, down from 1.065.

My question is: when should I start raising the temperature for a diacetyl rest? I’ve read that the last third of fermentation is considered to be a good time to start raising the temperature – is this idea based on achieving roughly 2/3 of the expected gravity loss due to fermentation? If I expect to get down to roughly 1.016 or so, I think this would mean starting to raise the temperature at about this time.

Any help would be appreciated![/quote]

dmtaylo2 · January 15, 2012, 1:16pm

If you want to do a diacetyl rest, you are correct. Right now is exactly the right time to do it.

tom_sawyer · January 15, 2012, 1:55pm

Seems like cheap insurance with no real down sides. I do it as a normal part of my lager process.

dan_s · January 15, 2012, 2:46pm

Thank you all for the help.

I think I’d like to go ahead and do one, but I have a new challenge this time around in that:

The temperature in my basement is now in the mid 50’s and will likely start to fall now that winter has officially arrived here in SE Minnesota, so I can’t us my ambient basement temperature to get to 60*
For the same reason, my Johnson temp. coltrolled fridge in the basement will not reach 60* if I simply reset the cut off from 50 to 60
I have a swamp cooler set up with an aquarium heater that works great for controlling ale temperatures, but the aquarium heater only regulates temperatures down to 64*
The temperature in the rest of the house is warmer than 60

In other words, I’m aiming for a temperature that seems to be right in between what I am set up for.

One thought I had was to somehow use the temp controlled basement fridge as a heating chamber, maybe making use of a light bulb? Not sure if this would produce enough heat, but I’m thinking there must be some way I can use the temp. controller and the fridge to reliably bring up the temperature by 10*.

tom_sawyer · January 15, 2012, 3:52pm

I think the house temp would be fine, I don’t think it would be a problem to use 65F. I’ve used low 60’s for mine. It certainly isn’t above the yeast’s tolerance and would probably speed the finishing of the fermentation. Then you can put it back downstairs, then into the lageing chamber for a step-down in temp.

conroe · January 15, 2012, 9:14pm

I let mine go until I see them slowing down then move into the house. It’s usually 10-15 above FG.

You can just let it ferment out and not raise the temp at all. The diacetyl rest is not really a necessity. I do it because it speeds up the process. It’s a attenuation and maturation rest. After that it’s crashed to freezing. There no reason to worry about the yeast. There is no more food for them and they have gone in to dormancy.

Traditionally at about four points above FG they’d move it to secondary and put somewhere near freezing. As it cooled slowly the last few points would carbonate the beer due to high solubility of CO2 at the lower temperature. It also scrubbed off any O2 picked up in the transfer.

Most homebrewing info on lager is a mix of traditional and modern brewing methods.

dan_s · January 16, 2012, 7:16pm

Thanks, guys – the carboy is now sitting in our back room, which hovers in the lower to mid 60’s.

Will take another reading in a week or so…

dmtaylo2 · January 16, 2012, 7:40pm

Even 70 F would be fine. It won’t hurt the flavor or make the lager taste overly fruity. It’s the first ~week of fermentation that really matters. After that, you can take the temp up and back down for lagering and you are good to go.