Every coffee roast moves through three phases in the same order: the drying phase, the Maillard (or browning) phase, and the development phase. Each one transforms the bean differently, each is bounded by a recognizable event, and the proportion of time spent in each is one of the clearest ways to describe — and reproduce — a roast.
This guide explains what happens to the bean in each phase, where the boundaries fall in temperature and time, how the phases typically divide up a roast, and what to watch for in each to roast more consistently.
The Three Phases at a Glance
A roast is a continuous process, but it's useful to divide it at two natural boundaries: the dry end (when free moisture is gone and browning begins) and first crack (when the bean fractures and development begins).
| Phase | Bean temp range | Typical share of roast | What's happening | What to watch |
|---|---|---|---|---|
| Drying | Charge → ~300–320°F (150–160°C) | 40–50% | Free moisture driven off; bean goes green → yellow; endothermic | Even heat, no scorching; a clean turning point |
| Maillard | ~300–320°F → first crack (385–415°F / 196–213°C) | 30–40% | Sugars + amino acids react; browning; aroma precursors form | Smooth, declining RoR heading into first crack |
| Development | First crack → drop | 18–25% (this is DTR) | Flavor finishes; acidity mellows; roast character builds | RoR positive and declining through the drop |
The percentages are typical proportions, not rules — they shift with bean density, roast level, and total roast time. But the order never changes, and the boundaries are always the same two events.
Phase 1: Drying
The drying phase begins at charge — the moment green beans hit the hot drum — and runs until the free moisture in the bean has been driven off. Green coffee holds roughly 10–12% moisture by weight, and most of that has to leave before the bean can begin to brown.
This phase is endothermic: the bean is absorbing far more energy than it releases, and much of that energy goes into evaporating water rather than raising bean temperature. Visually, the bean shifts from green to a pale yellow, and the smell moves from grassy and vegetal toward something closer to hay or toast.
Early in this phase, the bean temperature reading actually falls before it climbs. The cool beans pull heat out of the hot drum, the probe registers the drop, and the curve bottoms out at the turning point — typically 30–90 seconds after charge — before bean temperature begins rising for the rest of the roast. The turning point is the first repeatable landmark in a roast; a consistent turning point is a good early sign that charge temperature and batch size were consistent.
The drying phase usually accounts for the largest share of total roast time — often close to half. Rushing it tends to scorch the bean surface before the interior has dried; dragging it out risks a flat, baked character later. The goal is steady, even heat that ends with the bean fully dried and uniformly yellow, ready to brown.
Phase 2: Maillard (Browning)
The Maillard phase begins at the dry end — roughly 300–320°F (150–160°C) bean temperature, once free moisture is gone — and runs until first crack.
This is where the chemistry that defines coffee flavor really starts. The Maillard reaction is the same family of reactions that browns bread crust and sears meat: amino acids and reducing sugars combine under heat to form hundreds of new aromatic compounds and the brown pigments (melanoidins) that give roasted coffee its color. Caramelization of sugars overlaps here too. The bean darkens from yellow to tan to light brown, and the aroma turns bready, nutty, and sweet.
What you do with heat in the Maillard phase sets up everything that follows. The rate of rise should be declining smoothly through this phase — beans are warming steadily but the rate of warming is easing as they approach first crack. A RoR that's still climbing or spiking late in the Maillard phase usually means too much heat is being carried into first crack, which sets up a "flick" and a rushed development phase.
Many roasters think of the Maillard phase as the place where body and sweetness are built. Spend too little time here and the cup can taste thin; the right amount of controlled browning is what gives the finished coffee its depth.
Phase 3: Development
The development phase begins at first crack — the audible pop, typically 385–415°F (196–213°C), when internal steam and CO₂ pressure fractures the bean's cell walls — and ends at drop, when you remove the beans from the heat.
First crack is exothermic — the bean shifts from steadily absorbing heat to releasing some of its own as the cell walls fracture. That shift makes the rate of rise lively around the crack: a brief dip as moisture vents is common, sometimes followed by an upward "flick." This is the phase where the roast's final character is decided. Acidity mellows, sweetness integrates, and roast-derived flavors build. Drop early — during or just after first crack — and you get a light roast that emphasizes origin character: fruit, florals, brightness. Carry it further and the coffee moves through medium toward dark. Push far enough and you reach second crack — a second, sharper fracturing of the bean (typically 435–455°F / 224–235°C) that marks the threshold of dark-roast territory, where roast-derived flavor dominates origin character. Most specialty roasters drop before second crack.
The length of this phase, expressed as a fraction of total roast time, is the development time ratio (DTR) — usually targeted around 18–25%. But time alone isn't enough: the rate of rise has to stay positive and declining through the drop. A development phase that hits a good DTR on the clock but stalls (RoR falling to zero) will still taste baked, because the beans were held at temperature without the energy flux needed to finish developing.
First Crack calculates DTR automatically from the first-crack and drop events in your roast log — including on imported Artisan .alog files — so you can see how each roast's phase breakdown compares to the last twenty without doing the arithmetic by hand.
Why the Phase Breakdown Matters
Describing a roast by its three phases is the most portable way to talk about what happened. Two roasters with different drums, burners, and batch sizes can't directly compare burner percentages or airflow settings — but they can compare "50% drying, 30% Maillard, 20% development." The phase proportions abstract away the equipment and describe the bean's actual experience.
That makes phases the right unit for consistency work:
- —Dialing in a new bean: roast it a few times, cup the results, and note the phase breakdown of the one that tasted best. That's your target.
- —Diagnosing a bad cup: a thin, grassy cup usually points at a rushed drying or Maillard phase; a flat, baked cup points at development that ran long or stalled.
- —Tracking drift: green coffee changes through the crop year. If your phase proportions start shifting on the same profile, the bean is telling you something before it shows up in the cup.
The phases don't replace the underlying metrics — turning point, RoR, DTR, drop temperature, and weight loss all live inside this structure. They give you the frame those numbers hang on.
How the Phases Connect
The two boundaries between phases are themselves the most-watched events in roasting. The dry end marks the handoff from moisture removal to browning. First crack marks the handoff from browning to development — and it's important enough that roasters log its exact timing to anchor the development clock.
The thread running through all three phases is the rate of rise: it starts high after the turning point and should decline steadily across drying, Maillard, and development, staying positive all the way to the drop. A roast where RoR declines smoothly through every phase and ends positive is, in one number, a well-controlled roast.
See also: Rate of Rise in Coffee Roasting · Development Time Ratio (DTR) · What Is First Crack in Coffee Roasting? · FAQ