What is a "flick and crash" in coffee roasting?

At the start of first crack, evaporating moisture suddenly cools the bean probe (the "crash"). Immediately after, rapid exothermic cellulose caramelization releases sudden heat, causing the RoR to spike upward (the "flick"). A flick and crash destroys delicate floral notes and creates harsh astringency.

What does "baked" coffee taste like?

Baked coffee occurs when the Rate of Rise (RoR) stalls or crashes to near-zero during the development phase. The coffee lacks sweetness, possesses flat cardboard or stale bread flavors, and has a hollow aftertaste with no vibrant acidity.

What is the "turning point" in a roast curve?

When cold room-temperature green beans are dropped into a 400°F hot roasting drum, the bean temperature probe drops rapidly. After roughly 60 to 90 seconds, the probe temperature stabilizes and begins rising. That lowest temperature inflection point is the Turning Point (TP).

Why should the Rate of Rise (RoR) constantly decline?

A continuously declining RoR ensures the momentum of heat transfer decelerates smoothly as the beans lose moisture. Accelerating RoR late in the roast scorches bean surfaces, while an early stall prevents full internal caramelization.

What is the difference between First Crack and Second Crack?

First Crack (~390°F / 199°C) is an acoustic pop caused by internal steam pressure fracturing the bean structure. Second Crack (~440°F / 226°C) is caused by the physical fracturing of brittle woody cellular matrices as carbon dioxide gas expands, characteristic of oily Dark French and Italian roasts.

Free Coffee Roasting Rate of Rise (RoR) & First Crack Ratio Calculator

☕ Roast Timeline & Milestone Temps

Temperature Unit

Charge Temp (BT) Bean temp at charge

Yellow / Dry End Time (m:s) End of drying phase (~300°F)

Yellow / Dry Temp

First Crack Time (m:s) First audible pop

First Crack Temp

Drop / Dump Time (m:s) Roast end into cooling tray

Drop / Dump Temp

⚡ Phase Splits & RoR Kinetics

Development Ratio (DTR) -- Optimal 15% - 20%

Development Phase Time -- Post-crack development

Roast Phase Splits (Dry / Mid / Dev) --

Average Development RoR --

Maillard Phase Duration --

Roast Degree Level --

Scott Rao RoR Curve Audit --

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The Science of Coffee Roasting Thermodynamics

Coffee roasting is an endothermic-to-exothermic chemical metamorphosis where green dense coffee seeds are converted into fragile, aromatic brown beans containing over 800 volatile flavor compounds. In modern specialty roasting methodology (championed by Scott Rao and Rob Hoos), roasters monitor real-time bean probe telemetry in software like Cropster and Artisan.

The Three Cardinal Phases of a Coffee Roast

Drying Phase (Charge to Yellow ~300°F / 150°C): The beans absorb heat, evaporating 10% to 12% moisture until turning pale yellow with a bread-baking aroma (~40% to 45% of total roast time).
Maillard / Browning Phase (Yellow to First Crack ~390°F / 199°C): Amino acids and reducing sugars combine in complex Maillard reactions and caramelization, building sweetness, body, and melanoidin compounds (~35% to 40% of total time).
Development Phase (First Crack to Drop): Trapped steam and ( ext{CO}_2) violently rupture bean cell walls (First Crack). The bean transitions briefly into an exothermic reaction. Development time dictates the balance between bright fruit acidity and roasty caramel notes.

The Development Time Ratio (DTR) and Scott Rao's Rule

The single most predictive metric in specialty coffee roasting is the Development Time Ratio (DTR):

DTR (%) = (Development Time / Total Roast Time) × 100

Scott Rao's universal command: Keep DTR strictly between 15% and 20% (ideally 16% to 18%) while maintaining an uninterrupted, steadily declining Rate of Rise (RoR). If the RoR ever flattens or crashes during first crack, the coffee will taste dull, flat, and "baked."