What is Rate of Rise (RoR) in coffee roasting?

Rate of Rise (RoR) is the speed at which bean temperature increases during roasting, expressed in degrees per minute. It is one of the most closely monitored parameters in precision roasting, allowing the operator to actively steer the heat profile and anticipate transitions between the key phases of the process.

Rate of Rise is fundamentally a derivative: it measures not the absolute bean temperature but the speed at which that temperature changes at any given moment. If the bean probe reads 160°C at t=5 min and 170°C at t=6 min, the RoR at that instant is 10°C/min. It is this dynamic — not the temperature value itself — that guides decisions for professional roasters.

A well-managed RoR profile typically describes a declining curve: high early in the roast (sometimes 15–20°C/min just after charge), then progressively reduced as the batch advances. This controlled deceleration is intentional — it reflects the growing energy contribution of exothermic reactions (Maillard, caramelization) that partially self-sustain the process. A RoR that remains flat or spikes too late can create baked profiles or uneven development.

RoR is closely tied to the distinct phases of roasting. During yellowing (the drying phase), RoR is moderate and declining. As first crack approaches, it tends to drop more steeply — a sharp RoR crash just before first crack often signals insufficient energy in the system. After first crack, RoR management determines the speed of development and therefore the final flavor profile: a higher RoR during development produces brighter, more acidic coffees; a lower, extended RoR favors body and chocolatey notes.

In Cropster and Artisan roasting software, RoR is displayed in real time as a secondary curve overlaid on the temperature graph. Experienced roasters read this secondary curve as carefully as the temperature itself. Spikes or troughs in the RoR signal thermal imbalances — for instance a gas adjustment that was too abrupt, an inappropriate charge weight, or a variation in bean heat capacity due to origin or processing.

There is no universally 'correct' RoR value: everything depends on the coffee (density, moisture, processing), the equipment (drum, air roaster, capacity), and the target flavor profile. What matters is consistency and reproducibility: the same coffee, roasted with the same RoR profile, should produce a similar result batch after batch. This is what distinguishes reproducible artisan roasting from intuition-based approximation.

The Dynamic Variable That Defines Roast Quality

Rate of rise (RoR) — the temperature increase per unit of time in the roasting drum, typically measured in degrees per minute — is the single most discussed and debated metric in contemporary specialty coffee roasting practice. Its elevation from a simple measurement to a central craft concept can be traced partly to the influence of Scott Rao's The Coffee Roaster's Companion (2014) and partly to the proliferation of software like Artisan and Cropster that made real-time RoR graphing accessible to small roasters without expensive proprietary equipment. What these tools revealed was that the shape of the rate of rise curve — how it changes over the course of a roast — was as important as absolute temperature and time in predicting cup quality. A roast with a declining RoR (the standard "coasting" approach) produces different results than a roast with a "flick" — a deliberate acceleration of temperature shortly after first crack — even when both reach the same final temperature at the same total time.

The general consensus among specialty roasters is that a steadily declining rate of rise, without crashing to zero or going negative (indicating that bean temperature is actually falling despite continued heat application), produces the most consistent and quality-positive results. A RoR that crashes — often called a "flick" when followed by a brief acceleration or a "crash" when it simply drops to zero — typically indicates that the roaster reduced heat input too aggressively in the post-first-crack phase, creating the conditions for baked character. A RoR that stays flat or accelerates through development (without deliberate intent) risks scorching or tipping. The ideal declining RoR through development is a controlled, gradual descent that reflects ongoing but moderating chemical reactions — the roast is productive throughout but decelerating smoothly toward the drop point.

Practical Recommendations

For home roasters without software-assisted RoR tracking, the same principles apply but require more attention to manual observation. If your roaster has a bean temperature probe and a timer, track bean temperature at one-minute intervals through the roast and calculate the minute-by-minute temperature gain manually — or use a spreadsheet to automate this from timestamped notes. A simpler proxy is to listen for the rate and intensity of first crack and monitor how long the development phase feels relative to the total roast time. Experienced home roasters often describe developing an intuitive sense of RoR without numerical data, based on the smell of the developing coffee, the visual colour progression of the beans through the sight glass, and the acoustic character of first crack. This intuitive knowledge is legitimate and valuable, but anchoring it periodically against data — even manual temperature-and-time logs — prevents the gradual drift in judgment that can occur when intuition is the only calibration tool.