Roasting is heat applied for time. Green beans go in tasteless and dense; out comes coffee. Where the roaster stops the process — measured in colour, time, and internal bean temperature — decides how much origin character survives versus how much "roasted coffee" character takes over.
The landmark everything is measured against
Roasters navigate by two audible events: first crack, when the bean's moisture flashes to steam and ruptures it, and second crack, when the structure breaks down further and oils reach the surface. Every roast level below is defined by where the roaster stopped relative to those two. If you want the temperatures, the sounds, and the chemistry behind them, that's how coffee is roasted.
What matters here is simpler: past first crack the coffee is drinkable, and past second crack you're in dark-roast territory.
Light
Stopped shortly after first crack. Bean is dry, light brown, no surface oil. Internal temperature ~205–215 °C.
Origin character is loudest here. Acidity is highest. Sweetness is more delicate, more crystalline. Tasting notes will mention specific fruits and florals. This is the specialty default for filter coffee.
Light roasts are dense and harder to extract — they want hot water (94–96 °C), longer brews, and a slightly finer grind than medium.
Medium
Stopped well after first crack but before second. Bean is medium brown, no oil, often a uniform tobacco colour. Internal temperature ~215–225 °C.
Balanced between origin and roast. Acidity softer, sweetness rounder, body fuller. Tasting notes lean toward chocolate, caramel, nuts, dried fruit. The most forgiving roast level — works across V60, Kalita, AeroPress, French press without much fuss.
The most popular roast level worldwide. If you're unsure, this is the safe default.
Medium-dark and dark
Stopped at the start of second crack (medium-dark) or well into it (dark). Bean is dark brown to nearly black, often with surface oil. Internal temperature ~225–235 °C.
Roast character dominates. Smoke, dark chocolate, molasses, sometimes ash. Origin nuance is mostly burned away. Acidity drops sharply.
Dark roasts are fragile — already over-developed at the cellular level, easy to over-extract. They want cooler water (88–92 °C), shorter brews, and a slightly coarser grind. Espresso blends often run dark for body and crema.
What "medium-light" or "city roast" mean
Roasters use stage names from a tradition of US roasting:
- Cinnamon → very light, before development. Rare in specialty.
- City → medium-light. End of first crack.
- Full city → medium. Just before second crack.
- Vienna / Italian / French → medium-dark to very dark.
Specialty bags more often skip these and just say "light" or "medium" or list a development time.
How to read a bag for roast level
If colour is listed, trust it. If not, look for clues:
- Tasting notes lean fruity / floral → light.
- Tasting notes lean chocolate / caramel / nuts → medium.
- Tasting notes lean smoke / molasses / dark cocoa → dark.
- Visible oil on the beans → medium-dark or darker.
- A roast date close to a single-origin label with a producer name → almost always light or medium-light. Dark roasts are usually blends.
What this means for your recipes
When you switch from a medium to a light roast on the same brewer:
- Tighten the grind one notch.
- Raise the temperature 1–2 °C.
- Expect a longer brew.
- Don't expect chocolate notes — there shouldn't be any.
When you switch from medium to dark:
- Coarsen the grind one notch.
- Drop the temperature 2–4 °C.
- Expect a faster brew.
- Don't push for clarity — the bean isn't going to give it.
The recipe always has to match the roast. A "great V60 recipe" that worked on a medium will produce a thin, sour cup on a dark roast and a hollow, papery cup on a light roast.
