Should I Reduce Heat When First Crack Starts?
Yes — for most roasters and profiles. The exothermic reaction at first crack releases its own heat. Without reducing input heat, temperature can climb faster than intended, compressing development time and risking uneven roasting.
⚡ Quick Answer
Yes — reduce heat by 10–20% at the start of first crack in most cases. First crack is exothermic (the beans release heat), so even without adding more heat the temperature will continue rising. Without a heat reduction, Rate of Rise (RoR) often spikes and the development phase rushes past before flavors fully develop. Exception: if your RoR is already low and slowing, hold heat or increase slightly.
🎯 Popcorn Popper / Basic Roasters: If you can't control heat, work with what you have — adjust your batch size and charge weight to slow the roast. Less coffee = slower roast = more development control.
⚙️ Why Heat Reduction Matters
Exothermic reaction at first crack
First crack is triggered by a pressure release, which releases energy (heat) from the beans themselves. If you maintain or increase input heat simultaneously, RoR can spike dramatically — compressing the development window and causing uneven extraction later.
Smooth rate of rise through development
Ideal roast profiles maintain a declining but positive RoR through development. You want temperature to keep rising — but more slowly. A declining RoR (not flat or negative) through first crack produces the most complex, sweet cups.
When not to reduce heat
If your RoR has already dropped significantly going into first crack (below 3–4°C/min), hold heat or slightly increase. A "crashed" or stalling roast (RoR approaching zero) produces baked flavors — flat and lacking sweetness — regardless of development time.