Diacetyl rest question?

[Allekornbrauer]

Hello I am pretty new at brewing lager beer’s an I am wondering at what specific gravity would one want to start the ramping up for a Diacetyl rest. I do know it based on the recipe’s original gravity an the project Final Gravity.

 

[SoCal-Doug]

I don't subscribe to an exact gravity to begin a d-rest. Their needs to be live yeast and should be above 63F to 64F. The yeast should be well past "peak fermentation activity" (when most of the diacetyl's are being created) and slowing down. I've read anything from 75% to 95%. In theory, anything in that range or a bit beyond should be fine. Consider what we say about diacetyl in ales... "don't take it off the yeast too early, give it a couple days after fermentation is complete. Give the yeast a chance to clean itself up".

With most of my lagers, I ferment for 2 weeks at the desired temp (typically 49F to 54F depending on the recipe and yeast). Then the chamber is raised to 65F to 66F for 3 days. After that, it's reset to 33F and crashed for 2ish weeks prior to kegging. Nobody has ever detected diacetyl's in my lagers.

Side note on lagers... Some lager yeasts are notorious for generating sulfur. If you smell rotten egg farts, simply relieve the pressure in the keg once or twice a day for a week or so.

 

[LLBeanJ]

Like SoCal-Doug, I also don't pay much attention to SG as it relates to the D-rest. I will generally start raising the temp about 5 days into fermentation, hold it in the low to mid 60's for a few days and then cold crash once I've taken a gravity reading to verify it's at the expected FG. My lagers are typically in the keg and tapped at about 2 weeks after brewing, and they really start to hit their stride about 4-6 weeks post brew day.

 

[Gnomebrewer]

As Doug said, 75% to 95% is about right.
But, I've brewed dozens of batches of lager and used 6 different lager yeasts and NEVER had diacetyl. I pitch cooler than my ferment temp with a healthy pitch and plenty of yeast and a good burst of pure O2. So it's not compulsory to do. YMMV.
English ales, however, I have had some diacetyl.

 

[SoCal-Doug]

In judging (and tasting fellow club members beers) I see way more diacetyl in ales than lagers. I attribute this to when someone brews a lager they know they have to wait and can't get into a hurry. Most commonly with ales, the brewer looks at his airlock for 15 seconds and says "hey, no bubbles, let's keg it".

Patience grasshoppah!

 

[Dland]

Usually I bring a lager up to low-mid 60sF for a few days if the fermentation has been in the 50sF. For the D rest to work well, yeast should still be somewhat active.

As others have stated, it is not so much a specific temp or time. When fermentation starts to slow down, but is still going some is when I try to do the D rest.

 

[Jag75]

I've only done ales . I was taught to just let it do its thing and be patient. My beers are always 3 weeks in a fermenter.

 

[OceanBob5]

I have my first batch, a dark ale, in the fermenter, so you know how new I am to this brewing. At the end of the third day, I no longer saw any activity in the air lock for at least half a day ( I know a reading would be a good idea but I don't want to contaminate so I'm trying to avoid it on this first attempt). I moved the fermenter, which was sitting for the past two days at 66 degrees after I found the right spot in the house, to the floor near a heater vent. This brought the temp up to 72 this morning, and now, it is slowing showing bubbles again. Is this normal? Reading about a D-rest in Palmer, I thought it should be 'resting' (= no bubbling), or is this a good thing in that the yeast are still working and the temp rising caused them to clean up more?? I have much to learn!

 

[ESBrewer]

When you heat it up, gases will expand and also co2 is released from the beer so it may be bubbling slowly even if there is no more active fermentation. That being said, the higher temperature may increase the rate of fermentation if there is still something going on. The only way to know for sure is to measure the gravity.

So there is nothing wrong with the bubbling, just give it some time at 72F before you move forward.

 

[jack13]

Side note on lagers... Some lager yeasts are notorious for generating sulfur. If you smell rotten egg farts, simply relieve the pressure in the keg once or twice a day for a week or so.

hmm...I noticed that if a beer has a bit of a sulfur smell (it's usually much more smell than taste), that smell will go away as the beer sits out. Maybe within 10 minutes, even.

I had wondered if that was just my smell adapting (as smell tends to do).

I guess, then, the method you describe works because of the same phenomenon?

 

[SoCal-Doug]

Sulfur is very volatile. Meaning, it's a compound that easily transfers from a fluid surface to the air. If CO2 bubbles are present, or it is being stirred up, it helps the sulfur outgas and go away even faster.

Sulfur can "shut down" your sniffer making it harder to detect but I dont think the quantity of sulfur in fermenting beer has the strength to do that. That would be a good question for a chemical engineer. However things like hydrogen sulfide that smell similar (created in low and no oxygen environments, i.e. black mold) can shut down a sniffer (and hurt you) very quickly. Fortunately, beer does not generate such things unless something went horribly wrong.

 

[seatazzz]

Great post. I'm currently fermenting my first "true" lager at 50; it's still got krausen and plenty of action down below, so will probably wait another day or two before bringing it in the house for a d-rest. Haven't given it a sniff yet, but the ferment fridge smells fantastic if that means anything.