RoastLog

Coffee roast levels explained

"Light, medium, dark" sounds like just a color scale, but each level is really a description of how far you carried the chemistry inside the bean. As a roast goes longer and hotter, acids break down, sugars caramelize and then burn, oils migrate to the surface, and the bean loses mass. Knowing what changes at each stage lets you roast on purpose instead of by accident.

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Light roast

Light roasts are dropped shortly after first crack, typically before the temperature climbs much past ~205°C (400°F). The beans are light brown, dry on the surface (no oil), and they keep the most of their original character — the bright acidity, florals and fruit notes that distinguish one origin from another. This is why specialty roasters favor light roasts for single-origin coffees. The trade-off is that an underdeveloped light roast can taste sour or grassy, so development still matters.

Medium roast

Push a little further — toward roughly 210–220°C (410–428°F), well after first crack but before second — and you reach medium. Acidity softens, sweetness and body build, and you get the balanced, approachable cup most people think of as "coffee." The surface stays mostly dry. Medium is the most forgiving level for home roasters because the flavor window is wide and small timing errors are less punishing.

Dark roast

Dark roasts continue into or past second crack, generally around 225–240°C (437–464°F). The beans turn deep brown to nearly black and develop a sheen of surface oil. Origin character largely gives way to roast-driven flavor: bittersweet, smoky, chocolatey, sometimes ashy if pushed too far. Body can feel heavy, acidity is minimal. Dark roasting is less about the bean and more about the roast itself, which is why it's harder to taste where the coffee came from.

What changes across the scale

Color: tan → medium brown → dark brown/black.
Acidity: high and bright → balanced → low.
Body: lighter and tea-like → fuller → heavy.
Surface oil: dry → mostly dry → oily.
Origin character: pronounced → present → muted by roast.
Weight loss: lower (often 11–14%) → mid → higher (15%+).

A handy thing about that last point: because beans keep losing mass as the roast goes darker, weight loss % is a reliable at-home proxy for roast level — far more objective than judging by color under your kitchen light. Log green and roasted weight for each batch and you can target a level by the numbers.

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