What are roasting milestones in coffee roasting?

Roasting milestones are the key reference points during a roast that mark transitions between phases or signal important events in the bean's development. The primary milestones are: yellowing (beans turn from green to yellow, marking the end of the drying phase), first crack (beans begin audibly cracking as internal pressure is released, marking the start of the development phase), end of first crack, and second crack (if the roast continues into darker territory).

Milestones are what roasters use to navigate the roast in real time. Rather than relying solely on temperature targets, experienced roasters track the time between milestones - how long from charge to yellowing, yellowing to first crack, and first crack to drop. These time intervals, and the temperatures at which each milestone occurs, tell you how a roast is tracking against the intended profile.

Roasting software like RoasTime, Cropster, and Artisan allow roasters to mark milestones as they occur, automatically calculating the time spent in each phase. These logged milestones become the diagnostic record that helps you understand why one roast tasted different to another, and how to adjust the next batch to get closer to your intended result.