If there is one moment to listen for in a roast, it is first crack. It is the point where a batch stops being toasted green coffee and starts becoming drinkable, and it is the reference point nearly every roasting decision hangs on. Understanding what it is — and what you do with the time after it — is the single biggest lever a home roaster controls.
Open the roast log →As beans heat past roughly 196°C (385°F), the moisture and gases trapped inside build enough pressure to rupture the cell structure. The bean physically expands and audibly pops — a sharp, irregular sound a lot like the start of popcorn, though quieter and snappier. That popping is first crack. At the same moment the beans visibly swell, smooth out, and start shedding their papery chaff.
The exact temperature varies with your roaster, batch size and bean density, so don't fixate on a number. Train your ears instead: the start of first crack is what you log, and from that timestamp everything downstream is measured.
Before first crack, the beans are mostly drying and browning — there is little of the flavor you actually want to drink. First crack marks the beginning of the development phase: the stretch between first crack and the drop, where the heat finishes the chemistry that produces sweetness, body and balanced acidity. Stop the roast right at first crack and the cup tends to taste sour, grassy and underbaked. Carry development too far and the bright, origin-specific flavors flatten into generic roastiness.
The time you spend after first crack is where you shape the cup. A short development (pull soon after the pops begin) keeps a light roast vivid and acidic. A longer development rounds acidity into sweetness and builds body, leading toward medium and then dark roasts. Push far enough and you reach second crack — a quieter, crackling snap — which signals you are entering dark-roast territory.
Roasters quantify this with the development time ratio, the share of the total roast spent after first crack:
Most balanced roasts land somewhere around 15–25%. There is no single correct figure, but logging it lets you connect a number to a taste and repeat what worked.
Note first crack the instant you hear the first clear pops, then note your drop time. Pair those with green/roasted weight and a tasting note and you can see, batch over batch, how a bright cup differed from a baked one. RoastLog records first crack and drop in mm:ss and computes DTR for you automatically as you type.
Track your next first crack →Related: Development time ratio · How to roast at home · RoastLog app