I recently bought a bag of coffee from one of my favorite European roasters. When I opened the bag I was surprised to discover the coffee was quite a bit darker than I expected. Brewing the coffee revealed a flavor profile to match the color: bitter chocolate, roasted nuts, and — dare I say — ash.
Even though many specialty coffee drinkers prefer a light to medium roast, there’s still a significant number of people who prefer something darker. For them, coffee should taste like, well, “coffee.” And though I will admit my personal preference is for a coffee dropped closer to first crack than second, a good dark roast can be enjoyable if prepared properly. But dark roasted coffee needs to be brewed differently than light or medium roast coffee to get the best results.
Defining Dark Roast
Part of the problem of talking about roast levels is that there is no universally recognized standard as to what constitutes a dark roast. I discovered when I moved to Europe that one barista’s light roast is another barista’s French roast. If anything, coffee professionals use the term “dark roast” to mean “darker than I prefer”– whatever that might be.
Perhaps the most objective way of measuring roast degree is the Agtron scale. Agtron’s digital color analyzers use a 100 point scale to quantify color– the higher the number, the lighter the color. (The Agtron scale is also used to measure the maturity of tomatoes, amongst other agricultural products). The Agtron scale is widely used by larger coffee companies, but the high cost of the machine makes it less practical for smaller, boutique roasters, let alone consumers.
More widely used is the somewhat cumbersome “city” scale popularized by Sweet Marias. This scale uses the different stages of the roasting process (drying, color change, first crack, second crack) as a reference point, but with the rather curious designators “city,” “city plus,” and “full city”. To be honest, whenever a roaster tells me they “took this coffee to city plus” I just nod and try to pretend I know what they’re talking about.
For the purposes of this little article, we’ll simply define dark roast as coffee that is roasted until the beginning of second crack or later.
Different Grind Size
Brew a light roast and dark roast side-by-side and you’ll notice they behave very differently. Given the same grind setting, the dark roast will likely brew much faster.
During roasting, as the coffee approaches second crack, the cellulose begins to break down. In the case of very darkly roasted coffee, you’ll even see visible oils on the outside of the beans due to the damaged structure. This makes the coffee a lot more soluble as it’s easier for the hot water to move through dark roasted coffee, extracting the soluble compounds in the process.
But only if it were so simple. Dark roast is also more brittle and less dense, which means that it behaves differently when you grind it. Generally speaking, dark roast will produce more fine, dust-like particles. Depending on your grinder, this abundance of fine might clog your brewer, slowing down the flow rate.
As such, be prepared to experiment with different grind sizes. But in general, you can achieve a higher extraction with dark roasts compared to lighter roasts, so don’t be afraid of a coarser, faster-moving grind setting.
Lower Water Temperature
When brewing light roast coffee, it’s almost impossible for your brew water to be too hot. SCA standard is for the water to be between 195-205F. If I’m brewing a light roast I want that to be as close to 205 as possible, but if I’m brewing a dark roast, I will let the water cool down to 195F to minimize the bitter, astringent flavors that tend to dominate the finish of over-extracted dark roast.
The older SCA flavor wheel referred to those burnt, ashy flavors, perhaps inaccurately, as “dry distillates.” Those flavors dissolve after the organic acids and sugars, which take less energy to extract. As such, I find the “ideal” extraction for dark roast is lower than lighter roasts. While I might aim for a 20-21% solubles yield with a light roast, most dark roasts are going to taste their best in the 18-19% range.
Faster Brew Times
As an authorized trainer of the Specialty Coffee Association, I teach the standard SCA curriculum in my courses. When brewing coffee for myself, however, I find I prefer longer brew times with light roast coffee– typically around four minute brews, but up to five minutes for East African coffees. I find these longer brew times offer more sweetness and complexity in the cup.
With dark roast, however, I know that brews above three minutes are going to be overly astringent and dry; less chocolate and nuts and more ash and tobacco. As such, I aim for a 2:30-3:00 total brew time when brewing dark roast.
In short, if you’re brewing dark roast, use water on the cooler side of SCA standards, keep your brew times between two to three minutes, and be prepared to try a few grind sizes to optimize extraction. And if you’re inviting me over, it doesn’t hurt to have some cream around.