Second crack
also: 2C
A later, quieter, faster crackle in roasting as the bean's structure breaks down and oils surface; the door to dark roasts.
Second crack is the second wave of cracking sounds during roasting, arriving after first crack at higher temperatures, typically somewhere around 224 to 230 C (435 to 446 F). The sound is different: quieter, faster, and snappier, often compared to crackling cereal or breaking twigs, because it comes from the bean’s cell structure giving way rather than steam pressure.
Why it matters: second crack marks the transition into dark roast territory. Around here oils begin to migrate to the surface, the bean’s origin character fades, and roasty, smoky, bittersweet flavors take over. Roasters use it as a clear signal of how dark they are going.
Pushing well past second crack leads to very dark, oily, increasingly carbonized coffee. Many roasters stop at or just into second crack for a classic dark roast, or drop before it for medium and light. So like first crack, second crack is a decision point on the roast spectrum, not just a sound. The time between the two cracks is part of the development time.