What is a dark roast? Flavor, caffeine and how to grind it

When does a roast count as dark?

A roast usually counts as dark once it is well into second crack. Perfect Daily Grind notes that a roast showing only the first signs of second crack is probably still closer to medium. Wikipedia's roasting article puts second crack at about 224°C (435°F), versus about 196°C (385°F) for first crack.

The old names map onto that range. Wikipedia lists Full City at the start of second crack and Vienna in the middle. French comes at its end, and Italian is nearly black.

Time is another marker. Stumptown says its light roasts take about 10 to 11 minutes, and its dark roasts about 14 to 16 minutes. There is no industry-wide cutoff, so one roaster's "dark" can be another's "medium-dark."

What does a dark roast taste like?

A dark roast tastes mostly of the roast: bittersweet, low in acid and heavy in body. Stumptown says acidity and fruit fade after first crack, while caramel and chocolate develop.

Wikipedia describes the French stage as one where roast flavor dominates, and Italian as having burnt tones.

If you like a fruity, tea-like cup, look at a light roast instead. A medium roast sits in between.

Why are dark roast beans oily?

Dark roast beans look oily because the long roast pushes oils to the surface. Wikipedia notes that an oily coating is more common with darker roasts.

Oil on the surface tells you about roast level, not quality. It is one of the easiest ways to spot a dark roast in a bag.

Does dark roast have less caffeine?

It depends on how you measure it. By weight, the difference is small, and by volume, dark roast has a little less.

Wikipedia says caffeine stays stable up to about 200°C, so roasting removes little of it. But beans lose 15 to 18% of their mass and roughly double in volume as they roast. Wikipedia notes that a scoop of lighter roast holds more caffeine than the same scoop of a less dense dark roast.

So if you weigh your coffee, roast level barely changes the caffeine. If you measure with a scoop, a dark roast gives you slightly less.

How should you grind a dark roast?

Grind a dark roast a little coarser than you would a light roast for the same method. Counter Culture says darker roasts are more readily soluble and need a coarser setting.

Counter Culture gives the reason. A darker roast degrades the bean's cell structure, so it is softer and less dense. Softer coffees produce more fines, the particles under 200 microns, and fines extract fast.

In practice, start slightly coarser than your usual setting and adjust by taste. If a dark roast tastes harsh or ashy, it is often over-extracting. The grind converter gives a starting point for your grinder.

Which brew methods suit a dark roast?

Any method can work, and the choice is mostly about taste. Many people drink dark roasts as espresso or in a French press, where body is part of the appeal.

Whatever you brew, set the grinder for the method first. The method moves the grind setting much more than roast level does. Then use roast level to fine-tune, going a little coarser for a dark roast.

Stumptown's own example is its French Roast, which it lists as its dark roast pick. Check the bag for a roast date too, since roast level does not tell you freshness.