Rate of Rise (RoR)

Rate of bean temperature increase during roasting, expressed in °C/min. A stable and slightly decreasing RoR indicates a clean roast. A RoR that rises at the end (stall) may produce a baked taste.

Background & Context

Rate of Rise (RoR) is the rate of temperature change within the coffee bean during roasting, typically measured in degrees Celsius per minute (°C/min). It is the most important roast control variable for producing consistent, high-quality coffee. RoR is not the same as drum temperature — it measures how quickly the beans themselves are absorbing heat. During a standard specialty roast, RoR follows a characteristic curve: starting high at charge (20–30°C/min) as the cold beans absorb heat rapidly, then declining through the Maillard phase and development phase toward a gentle slope (typically 2–5°C/min at first crack). The ideal RoR curve for specialty coffee is a smooth, controlled decline — 'a mountain with a long, gentle slope on the right side', as roast trainer Scott Rao describes it. A RoR crash (sudden sharp decline) during the Maillard phase produces baked flavours. A rising or flat RoR at development (termed 'RoR inversion') can produce harsh, spiky acidity. Modern roasting software — Cropster, Artisan, Ikawa Data — plots RoR in real time, allowing roasters to make interventions by adjusting gas, airflow, or drum speed. The integration of RoR monitoring with flavour analysis has been the biggest technical advance in specialty roasting since the 1990s.

Practical Use

For those using a home drum roaster or an entry-level roasting machine: even without live RoR plotting, you can observe RoR by timing when first crack begins and how fast it progresses. A first crack that begins explosively and ends within 30 seconds suggests a steep, uncontrolled RoR. A rolling, even crack that lasts 60–90 seconds suggests a well-managed RoR decline. Software is available (Artisan is free) for many home roasters that adds RoR logging capability.

Related Terms

Related terms: Development phase — where RoR control is most critical. First crack — the roast event where RoR monitoring intensifies. Baked roast — the defect caused by RoR crash. Agtron — the end-point measure complementing RoR during-roast monitoring.