Goosing a stalled ferm: How hot is too hot?

[McKnuckle]

Got a brew that has fermented from OG 1.066 down to 1.026 over eleven days. It got to 1.027 in six days (@ 68F), then only a single point in the subsequent five (@ 71F). This is with WLP001.

Being a sweet stout, it has 2 oz of lactose in 3 gallons, and 10% crystal in the grain bill. Also I mashed at 156. So a bunch of unfermentables are in there for sure, contributing to a higher gravity.

Just to be sure it was done, I moved the pail to my furnace room where it has gotten to 78F overnight. The beer is now gently fermenting again, little yeast blobs rising and falling. Is it worth doing this? I think I'm going to let it ride for 24 hours total at that temp and then move to a colder place for settling.

 

[billl]

I wouldn't worry. The off flavors you might get from higher temps almost exclusively occur during the initial yeast growth phase.

 

[McKnuckle]

Yes, that's the common wisdom I'm going with here, thanks. A bit curious why we don't employ warmer temps at the latter stage of primary more routinely. Not just 70 for a d-rest, but 75 or more to really kick the yeast in the pants a bit.

 

[winvarin]

Yes, that's the common wisdom I'm going with here, thanks. A bit curious why we don't employ warmer temps at the latter stage of primary more routinely. Not just 70 for a d-rest, but 75 or more to really kick the yeast in the pants a bit.

Jamil Z recommends just that. His advice is that your temp should always remain steady or rising until you are cooling the beer to promote flocculation. His only exception to that is the fermentation schedule used by Fullers (but that is a story for a whole different thread)

Based on JZ's recommendations I use the rising temp technique with success for almost all beers.

I pick a temp that I want to use for the bulk of my ferment based on the desired ester contribution, then get my wort to that temp before pitching.

Then I hold my beer there as primary ferment progresses. As I see signs that the beer is slowing down, I increase my temp by about 1f per day until I am 3-5f above my ferment temps. I hold the beer there for at least another week before tasting/smelling a gravity sample.

If the beer is free of off flavors and aromas an has reached my desired level of clarity, I package. If there are still some fermentation byproducts noticeable (usually acetaldehyde or diacetyl) I leave it as is for a few more days. Depending on the level of byproducts I detect, I may even bump the temp another degree or 2. And even give the fermenter a little swirl to kick up the yeast.

If everything else is OK but the beer is a little cloudy still, I SLOWLY begin dropping the temp. Temperature stress is a real thing. Any rapid large change in temperature can cause the yeast to release those byproducts they just cleaned up back into your beer.

That's why I hate the term "cold crash". The yeast will treat your beer better if you send them gently off to sleep by reducing the temp slowly over a few days rather than dropping them off a 10-15 degree cliff over a period of a few hours.

 

[McKnuckle]

Temperature stress is a real thing. Any rapid large change in temperature can cause the yeast to release those byproducts they just cleaned up back into your beer.

Interesting and a bit worrisome. I'll admit to not caring much about this when cooling down, and I'll bet it's common practice among many brewers to cold crash immediately when fermentation is over. I'll have to poke around and research this, but point taken. Thanks.

 

[winvarin]

Interesting and a bit worrisome. I'll admit to not caring much about this when cooling down, and I'll bet it's common practice among many brewers to cold crash immediately when fermentation is over. I'll have to poke around and research this, but point taken. Thanks.

All other things considered, it's a matter of degrees (pun intended). If you've done well in all other areas, I don't think you'd ever ruin a beer by cold crashing. It would be more a matter of "hmm, I didn't detect this flavor when I took my gravity sample, now I pick up a hint of X."

Based on how he's talked about it, I don't even think your chances of it happening are 100%. It's more of an increased chance that something could happen.

Just another one of the many fine tuning dials that we have at our disposal