I read about Brewers saying they ramp up their fermentation temperature to the yeasts high end, sometimes past the yeasts published fermentation range, and let it sit for a few days to let the yeast ‘clean up.’ If this is a common practice and/or a good idea, how long after fermentation can/should the hotter temperature be introduced? I have a Belgian dark strong that has been sitting at 68 for 3 weeks.
After three weeks, there probably wouldn’t be any benefit. I’m assuming gravity stopped dropping at least a week ago?
I pitch and hold at whatever the target temperature is, then ramp to 22°C once I start seeing linear attenuation (two consecutive days with large gravity drops). That’s generally day 3-4 for ales. Hold there until 3-4 days after FG is reached, and then as long as it tastes good go straight to cold crashing.
Sean is right - with a healthy pitch (cell vitality as much as cell numbers), you don’t need as much “clean up time” as was previously thought. A diacetyl rest for lagers and some colder fermented ales may be advisable as fermentation slows, because it allows for the removal of the diacetyl as well as helping reach terminal gravity a bit quicker (typically at a point which is well past any off flavors or adverse compounds arising). I brew lagers mostly, so I like to follow Marshall’s regiment of pretty strict temperature control to get the lager to finish pretty quickly compared to past methods. (Look into Brulosopher.com).
Smell and taste it. Do you get any off aromas or flavors [diacetyl (movie popcorn butter or butterscotch), acetaldehyde (sour greeen apple jolly rancher), etc.]? Those are typically the sort of compounds that yeast will clean up. If you detect any, you can always use a fresh pitch of yeast to clean up after them. It’s called krauesening. The two primary uses are natural carbonation (without having to use priming sugar) and to help clean up after high flocculating yeast that drops out of suspension too soon.
From BYO, they recommend 3 days for ales and 7 days for lagers for a diacetyl rest.