The most common way to describe coffee roast levels is by the colour of the roasted beans, ranging from light to dark (or extra dark). As coffee beans absorb heat in the roasting process, their colour becomes darker. Oils appear on the surface of the beans at higher temperatures. Because coffee beans vary, colour is not an especially accurate way of judging a roast. But combined with the typical roasting temperature that yields a particular shade of brown, colour is a convenient way to categorize roasting levels.
Medium-dark roasts have a richer, darker colour with some oil beginning to show on the surface of the beans.
A medium-dark roast has a heavy body in comparison with the lighter or medium roasts.
The beans are roasted to the beginning or middle of the second crack,
about 225°C (437°F) or 230°C (446°F). The flavours and aromas of the roasting process become noticeable, and the taste of the coffee may be somewhat spicy.