Flick and Crash

In the context of specialty coffee roasting, the 'crash and flick' refers to a specific, undesirable behavior of the Rate of Rise (RoR) curve—a metric that tracks the speed at which bean temperature increases over time. The 'crash' occurs when the RoR drops precipitously as the coffee enters first crack, while the 'flick' is the subsequent, often reactive, surge in the RoR. This phenomenon is widely recognized as a failure in roast management, as professional standards generally favor a smooth, steadily declining RoR throughout the entire roasting process.

The physical mechanics behind this pattern are rooted in the thermodynamics of the coffee bean. As coffee approaches first crack, it undergoes an endothermic-to-exothermic transition. The internal pressure generated by steam—which can reach over 350 psi—shatters the cellular structure of the bean. This rapid release of energy and moisture can cause the bean probe to register a sudden cooling effect, leading to the 'crash.' If a roaster has reduced heat too aggressively in anticipation of this event, the RoR may stall or plummet, prompting the operator to increase heat input to regain momentum, which then triggers the 'flick.'

For the roaster, the crash and flick is a diagnostic indicator of poor thermal control. The 'flick' is particularly problematic because it often results from an overheating of the roasting environment or the drum surface. When the drum surface temperature spikes, it can sear the outer layers of the beans, similar to searing a steak. This creates an uneven roast where the exterior is over-developed or charred while the interior may remain underdeveloped, leading to a loss of the coffee's inherent delicacy and sweetness.

From a sensory perspective, the impact on the final cup is significant. Coffee that has undergone a crash and flick is frequently described as 'baked' or 'flat.' Even if the roast color appears uniform to the naked eye, the chemical changes caused by the flick often introduce harsh, charred notes that mask the nuanced flavor profiles of high-quality specialty beans. This makes the phenomenon a primary concern for roasters aiming to highlight the unique characteristics of a specific origin.

Managing this issue requires precise energy modulation. Roasters must learn to anticipate the exothermic nature of first crack without over-correcting. By maintaining a consistent, gentle decline in the RoR, roasters can avoid the reactive adjustments that lead to the flick. Modern roasting software, such as Cropster, has become an essential tool in this process, allowing roasters to visualize their RoR in real-time and refine their gas and airflow adjustments to prevent these sharp fluctuations.

While the crash and flick is a staple topic in home roasting forums and professional training, it remains a subject of ongoing study in coffee science. Research into roast profiles—such as studies examining the development of titratable acidity—continues to quantify how different energy inputs affect the chemical composition of the bean. Understanding these dynamics is crucial for the industry, as it bridges the gap between raw agricultural product and the refined sensory experience expected by the consumer.

Ultimately, the story of the crash and flick is one of mastery over the roasting environment. It serves as a reminder that coffee roasting is a delicate balance of thermodynamics and timing. For the farmer, who works to produce high-quality green coffee, the roaster's ability to avoid such defects is the final step in ensuring that the labor and care invested at the origin are preserved in the cup.