Simply using light, medium, and dark doesn’t make sense because of the lack of agreement of what they mean; one person’s medium is another person’s light. Moreover, light can encompass quite a range of colors. Names like city, full city, French, and cinnamon are just as nondescript, as there’s no standard for what color they actually correlate with. Terms like strong, bold, deep, and heavy are even more egregious, as they either refer to the concentration of the brew (strength) or could possibly refer to its viscosity. Clever marketing brought us these terms and every coffee professional wishes these words would vanish from the roast level lexicon. Much to my dismay, I’ve never come across any terminology that works particularly well for describing roast levels.

Is there a more objective method that could be used? Yes. In fact, there are several, all of which are imperfect and all of which are distant and somewhat meaningless to the typical coffee drinker.

We can be referential to the stages of roasting, and talk about roast level as the time before or after first or second crack. To an experienced roaster and especially to one familiar with a particular coffee (different coffees roast differently, as you’d expect), this is a fairly useful method of communicating roast level. However, as the length of the roast and events within the roast are, by definition, dependent on the roast profile, using the cracks as reference points are only useful if there is some knowledge of the profile.

Another method that is often used by scientists is weight loss. As the roast progresses, not only does the bean expand, nearly doubling in size by the end, but it loses a lot of weight as moisture evaporates and solid matter is converted into volatile compounds that leave the bean. Very light roasts will lose around 12 percent of their weight while very dark roasts can lose as much as 30 percent of their weight. The minor drawback to this system is that weight loss depends on initial weight, which is heavily influenced by moisture content. While most green coffees tend to be in the 9 to 12 percent moisture range, not all of them are, and if not stored well, their moisture content can change. A coffee with a higher moisture content will have a greater weight loss than one with a lower moisture content because more water (and the weight it added) will be driven off.

Did you know?

The first webcam was built in 1991 by computer scientists to keep track of how much coffee was in the coffeepot in the Trojan Room, a computer lab at the University of Cambridge.

This is fairly minor problem for small roasters because even in the extreme case, the final weight loss between a high to low moisture content coffee will be pretty small. On the other hand, roasters who roast very large quantities of coffees or roast particularly dark may end the roast by quenching the coffee with a fine mist of water. While the expectation is that the water evaporates immediately, thereby cooling the coffee quickly, some water may remain and add weight back to the beans. In my opinion, the biggest problem with this as a tool is that training consumers to calibrate colors to weight loss may never be very successful; people just aren’t used to thinking of weight and color as parallel ideas.

The last method that can be used to talk about roast color is the actual amount of lightness! More specifically, we can measure the amount of light reflected off the bean or grounds and assign an arbitrary number to that particular amount of reflectance. This is already a common practice in the coffee industry, and the arbitrary numerical scale already exists. All one needs to make sense of it is a spectrophotometer, a machine that measures the reflectance or transmittance of a specific wavelength of light, and the coding that translates the number to a color. The latter part is simple, as one can create and even buy already-made colored discs that correspond to the numbers. The hard part is that spectrophotometers are expensive machines and usually only larger companies purchase them. Just as tricky is the consumer side of things, much like with weight loss, few consumers are going to learn which number corresponds to which roast level.

In the end, there is no perfect way of conveying roast level to someone else without showing them the bean. So, we’ll just continue as we always have, using the tools we have on hand. Hopefully, someone will come up with something better someday. 

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