tags: [] - coffee/roasting aliases: - First crack - Second crack - Crack in roasting

First & Second Crack¶

Tags: #coffee/roasting Aliases: First crack, Second crack, Crack in roasting Related: Roasting Methods MOC | Roast Profile | Roast Development Ratio | Light Roast | Maillard Reaction Status: ✅ Complete

Overview¶

First crack and second crack are two distinct audible events that occur during coffee roasting, each produced by the physical fracturing of the coffee bean's internal structure under the pressure of expanding gases and moisture. First crack (occurring at approximately 185–205°C) marks the transition from raw to roasted coffee and is the reference point for all roast level definitions — light roasts drop shortly after first crack; dark roasts develop through second crack. Second crack (approximately 220–230°C) marks a more violent structural fracture as oils emerge from the bean and carbonisation begins.

First Crack¶

Temperature: Approximately 185–205°C bean temperature (varies by roaster, batch size, and green coffee density)

Cause: Water vapour and CO₂ generated by Maillard reactions inside the bean build pressure until the bean's cellular structure fractures. The fracture produces an audible "pop" similar to popcorn; the bean expands significantly as the internal cell structure opens.

What it marks: - Transition from endothermic to exothermic reaction in the bean - Bean expansion and colour darkening - Significant CO₂ release - The beginning of the roast development phase

Sounds like: A rapid series of pops; similar to popcorn but generally softer; rolling crackle lasting 1–3 minutes

Light roast drops here: Coffee dropped within 30–90 seconds of first crack start is a light roast. Coffee allowed to develop 2–4 minutes after first crack is medium.

Second Crack¶

Temperature: Approximately 220–230°C

Cause: The bean's cell wall structure (primarily lignin and cellulose) fractures further as expanding gases exceed the tensile strength of the carbonised outer shell. Oils, previously trapped inside the bean, are forced to the surface.

What it marks: - Dark roast territory (medium-dark to dark roast) - Oil emergence on the bean surface - Beginning of significant carbonisation - Loss of most origin character - Bittersweet, dark chocolate, roasty flavour dominates

Sounds like: More rapid, higher-pitched cracking than first crack; more frequent; continuous crackling

Between First and Second Crack¶

The space between first and second crack is where most specialty coffee development occurs: - Light roast: stopped shortly after first crack - Medium-light: 1–2 minutes after first crack - Medium: 2–3 minutes after first crack; nearing second crack - Medium-dark: at the onset of second crack - Dark: into or through second crack

Key Facts¶

First crack: ~185–205°C; bean fractures as CO₂/steam pressure exceeds cell wall strength; marks start of development phase
Second crack: ~220–230°C; cell wall carbonises and fractures further; oils emerge; dark roast territory
First crack is exothermic — it releases heat; rate of rise may stall briefly, then continue
Specialty coffee typically targets light to medium development between first and second crack; rarely proceeds through second crack
Development Time Ratio (RDR) is measured from the start of first crack to drop

References¶

Changelog¶

Date	Change
2026-04-28	Note created
2026-05-03	Compliance review: added `---` separator before copyright

This article is part of All-About-Coffee.com - The comprehensive coffee knowledgebase.