The process of roasting coffee wakes up the incredible, complex flavors that lie dormant within green coffee beans. Roasting coffee is often referred to as an art, in recognition of the combination of skill and talent it takes for a roaster to coax the maximum potential from a particular variety of coffee, with no two types of green coffee beans necessarily responding to the exact same roasting treatment.

Coffee beans are roasted by putting them in a rotating chamber heated, whether by a live fire, gas, or electricity, to a temperature range between 400 and 500°F (205 and 260°C). As the beans heat up, they give off their last traces of residual moisture and finally, suddenly “pop” with a distinctive crackling noise—expanding slightly in size in a phenomenon similar to that of popcorn popping. As roasting continues, the beans begin darkening in color. Meanwhile, the heat breaks down their cellular structure, unlocking aromatic oils that continue to develop in the high temperatures. At the same time, compounds known as polysaccharides transform into starches, then sugars, and begin to caramelize, adding sweetness and richness to coffee’s distinctive flavor.

Depending on the particular beans being roasted, the style in which the coffee will be brewed, and the tastes of a particular region or of the individual coffee drinker, coffee roasts may range across several different distinctive shades:

Cinnamon Roast. The lightest roast, resembling the color of cinnamon and also known as Light Roast, Institutional Roast, Half City Roast, or New England Roast. Used largely for mainstream commercial coffees, these coffee roasts yield light, acidic-tasting coffee with little body.

American Roast. Light or medium brown in color, and also called Medium Roast, American Roast coffee beans are also distinguished by their dry-looking surface. These roasts have notes of rich, sweet flavor to balance their acidity.

City Roast. Slightly darker, City Roast coffee beans have a little more flavor and less acidity.

Full City Roast. Also called High Roast or Light French Roast, Full City Roast coffee beans develop a deep brown color, with spots of shiny oil on their surface, and a rich coffee flavor.

Continental Roast. Longer roasting develops a glossy surface of oils on the darker brown Continental Roast coffee beans, also called Dark Roast coffee. Smoky and sweet flavor overtones develop.

French Roast or Italian Roast. Still darker shades of brown slightly beyond Continental Roast, French or Italian coffee roasts have a rich, complex, distinctively smoky and caramelized flavor.

Espresso Roast. The darkest of coffee roasts, Espresso Roast coffee beans look almost black and very shiny with coffee oils. Their pleasantly charred flavor comes to the forefront, blending with other distinctive coffee notes.

Note that the level to which coffee beans are roasted does not significantly affect the caffeine level in a brewed cup. While espresso drinks deliver more caffeine per sip, for example, that is due not to the level of roasting but to the concentration at which espresso is brewed. The stronger any cup of coffee is brewed, resulting from using a higher proportion of coffee to water or from leaving coffee and water in contact longer, the more caffeine it will contain.