How bad will it be?

Yesterday I pitched 2 different Brett-B yeasts into a split 5 gallon batch for a side-by-side comparison, and will be using both cakes for separate 7 gallon batches later.

They are both in the same swamp cooler and I had planned to keep the temperature somewhere between 70 and 75, but when I checked this morning, both were going strong (foam up the blow-off tubes), and the water temperature in the swamp cooler was 82 F.

I checked the heater and sure enough it had been set high - don't really know what happened.

It is now only 18 hours since pitching and I have lowered the temp to 77 F. Will probably lower it again later; don't want to do it too quickly.

How much damage have I done, if any?

Wyeast lists 75 F as the top of the range for it's Brett products. White Labs doesn't list any temperatures.

Should be fine, I let my Brett go like a saison yeast, pitch around 70 and let it rise as high as it wants. 80 is about as warm as it gets and no complaints here.

I've never pushed Brett B that high. Brett has the same variability (or maybe even greater) than Saccharomyces. I’ve had Brett luck fermenting White Labs Brett C in the 80s, very bright peachy. On the other hand Wyeast Brett A was terrible that warm, loads of burnt rubber bands. Hopefully it turns out well (let us know), best of luck!

I'll update as I find anything else. Planning on taking a sample tomorrow to see what is going on. Currently it is at 75 F. I'm thinking I'll keep it there for a couple of days and then push it back up above 80 to finish it off.

After 3 days I took a gravity reading, and both were 1.022/1.024, down from 1.058 (60% attenuation) and still working. I was adding 5% simple sugar which I had as part of the original recipe.

Taste was fine. Plenty of flavor (difficult to describe), not really fruity as expected, but certainly no off flavors. Looking good.

Started to increase temps today (day 5) since activity is just about done. Going to increase it a couple of degrees a day up to 82 again and leave it for a few days to finish off before dropping it again.

Probably be a couple of weeks before I check it again.