https://beerandbrewing.com/homebrewing-a-kolsch/ Place the wort in a 60?F (15?C) fermentation chamber for 5–7 days. Raise the temperature to 65?F (18?C) for 1 day for a diacetyl rest. Rack the beer and age at 35?F (2?C) for 21–30 days, then keg or bottle.