First Crack

First crack is an exothermic event where built-up steam and CO2 break through the bean's cell walls. The beans visibly expand, double in volume, shed silver skin, and transition from green-yellow to light brown. Roasters targeting light, origin-expressive profiles often drop the batch shortly after first crack completes. The sound, timing, and energy of first crack provide critical feedback about the roast's heat application and the coffee's moisture and density.