Rate of Rise (RoR) is the first derivative of the bean temperature curve: it measures how many degrees per minute (or per 30 seconds, depending on the logging software) the bean mass temperature is increasing at any given moment in the roast. A bean probe reading 180°C and climbing at 8°C per minute has a RoR of 8. Two minutes later at 195°C and climbing at 5°C per minute, the RoR has dropped to 5. The absolute temperature matters; the rate of change matters more.
The metric gained widespread adoption in specialty roasting circles through software platforms like Cropster and Artisan, which began making real-time graphical RoR curves accessible to small and mid-sized roasters in the 2010s. Before logging software, experienced roasters read RoR intuitively through bean color progression, chaff behavior, crack timing, and smell — valid methods, but imprecise and difficult to reproduce. The curve visualization formalized what master roasters had always sensed, making RoR legible to a much wider audience and enabling data-driven quality control across multiple operators.
The Declining RoR Principle
The industry consensus — built on the work of roasting educators including Scott Rao, Willem Boot, and the trainers at the Specialty Coffee Association — is that a steadily declining RoR produces better cup quality than a flat, rising, or erratic one. The logic is thermodynamic and chemical. Coffee beans are poor thermal conductors and absorb heat unevenly. A declining RoR means the roaster is applying progressively less aggressive heat input as the roast proceeds, allowing the developing bean to process heat uniformly rather than receiving a constant or increasing external push.
In practical terms, a declining RoR supports what roasters call “even development” — the conversion of starches to sugars, the Maillard browning reactions that create caramel and chocolate notes, and the pyrolysis reactions that produce the aromatic complexity of a well-roasted bean. When RoR declines smoothly from a peak of perhaps 12 to 15°C/min at the midpoint of the roast to 3 to 5°C/min at first crack and through development, the bean mass develops with relative uniformity from surface to center. When RoR is flat or rising, the exterior of the bean risks overheating relative to the interior — producing the surface scorching and underdeveloped center that characterizes many common roast defects.
The declining RoR model is not absolute. Certain roasters, particularly those working with fluid bed (air) roasters or with very high-density, very high-altitude beans, deliberately hold a flatter RoR through specific phases to compensate for lower thermal mass or to extend development time without adding total color. The principle is a starting framework, not a law — but deviations from it require a specific reason, not ignorance of the baseline.
Reading Flicks, Stalls, and Crashes
Three RoR events are diagnostic red flags that every roaster should be able to identify on a curve. A flick (also called a RoR spike) is an upward deviation — the rate of rise increases when it should be declining. Flicks commonly occur around first crack, when the exothermic crack reaction releases heat and can temporarily inflate the bean probe reading. A brief flick at crack is expected and can be managed with a gas reduction ahead of crack. A flick that is not managed — that results in sustained elevated RoR through development — is associated with underdeveloped centers and hollow cup character.
A stall is the opposite: RoR drops to zero or near-zero, meaning the bean temperature has plateaued. Stalls most commonly occur when a roaster charges a large batch relative to drum capacity, drops the batch at too low a charge temperature, or reduces gas aggressively after turnaround without adequate airflow. A stalling RoR is problematic because the beans are continuing to undergo chemical transformation — they are browning — but without the thermal driving force to complete development properly. Stalled coffees frequently cup flat and baked, lacking both brightness and depth.
A crash is a sustained, steep RoR decline that goes too far too fast — from a high peak to near-zero well before crack. Crashes often result from applying maximum airflow too early in the roast, pulling heat away from the bean mass before adequate development energy has been absorbed. Crashed curves produce coffees that may measure correctly on an Agtron but taste underdeveloped: grassy, astringent, thin. Identifying a crash on the curve in real time — by watching for RoR dropping faster than a degree or two per minute at the right phase — and compensating with a modest gas increase is a core live roasting skill.
RoR and Development Time
Rate of Rise connects directly to development time (DT), the interval between first crack and drop. Development time is typically expressed both in absolute seconds (e.g., 90 seconds) and as a percentage of total roast time (e.g., 22 percent). The specialty industry’s general guideline — based on empirical work by Scott Rao and subsequent refinements — is that 20 to 25 percent DT produces well-developed coffees without excessive roast flavor. But DT percentage means little without RoR context.
A coffee dropped after 90 seconds of development with a RoR of 8°C/min at drop is not the same as a coffee dropped after 90 seconds of development with a RoR of 2°C/min at drop. The first bean has continued to develop aggressively during those 90 seconds; the second has developed slowly, accumulating less total thermal energy. The practical implication is that target DT must be calibrated to RoR at drop — faster RoR at drop requires less DT to achieve similar development; slower RoR allows longer DT without over-roasting. Roasters who learn to read RoR at crack and during development, rather than watching the clock alone, produce more consistent results across varying green coffee densities, moisture contents, and batch sizes.
Why RoR Matters for Flavor
The connection between RoR management and cup flavor is real but not always intuitive. The core mechanism: coffee’s most delicate aromatic compounds — the aldehydes, esters, and terpenes responsible for floral, fruit, and citrus notes — are volatile and degraded by excessive heat. A well-managed declining RoR limits the total thermal energy applied to the bean, particularly in the development phase, which preserves more of these volatile compounds in the finished roast. Over-roasted coffees — produced with high RoR, long development times, or excessive total roast time — lose these volatile compounds first, leaving behind the more thermally stable pyrazines and furans associated with roasty, nutty, and dark chocolate notes.
This explains why lighter, faster roasts often show more origin character (the terroir and variety-driven aromatics) while darker, longer roasts show more roast character. RoR management is the tool roasters use to position a specific coffee on that spectrum intentionally. A roaster who understands RoR is not just avoiding defects — they are making deliberate decisions about how much of the bean’s genetic and geographic potential to preserve versus how much to transform through the chemistry of heat.