By December 3, 2010 Read Article
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Agtron Numerology

If you’ve ever read a review on, you’ve most likely noticed a pair of Agtron numbers listed below the attribute scores. Unless you work in the coffee industry, you probably don’t have a clear idea what these numbers represent. The inquisitive have undoubtedly copied and pasted the term Agtron into search engines to yield information about the Nevada based company of the same name that manufactures roast color readers. Color readers are used in a wide variety of industries, from paving stones to pharmaceuticals, wherever consistency of color is important in a given product.

Color can be determined a number of different ways, Agtron uses “near-infrared abridged Spectrophotometers” to reflect light on a sample of coffee in order to assign a specific value, which we read as a number. The smaller the number, the darker the roast. There are other companies out there that manufacture color readers such as Javalytics, Hunter Lab and Photovolt, as well as Probat’s Colorette and Fresh Roast’s Color Track, but the king of the heap, at least in coffee industry nomenclature, remains Agtron. In fact, even when companies use another brand of machine they still may refer to Agtron numbers, sometimes converting their numbers to one of the Agtron scales. Many in the coffee industry are just as likely to use the word Agtron as a noun, in reference to the popular spectrophotometer, as well as a verb, to describe the process of taking a color reading on one of these machines.

In consulting work, we find it necessary to calibrate our M-Basic Agtron machine, which reads on the so-called Gourmet Scale, with the color reader that is being used by the companies we work with. The color reader may be a different brand, different model type (such as Agtron’s E-20, which reads on their Commercial Scale) or even the same model we use. Although each machine is consistent to itself, we find there may be a variance in the numbers generated by different color readers.

But I digress. The questions remains, why two numbers? The two numbers represent the whole bean and ground color value for each coffee. We gain additional insight about the roast of a coffee when we note the delta between the readings of whole bean compared to ground coffee. In general, the darker the roast, the narrower the delta, while lighter roasts tend to show a wider range. We do not take roast color into consideration when undertaking sensory assessment of coffee; we take Agtron readings only after the evaluation process of the coffee is complete. This added information will often corroborate the characteristics we noticed in the cup. For example, a narrow delta on a light roast may explain the limited aromatic range of the coffee.

Why should consumers care about the numbers? Well, they shouldn’t, as long as they know that small groupings of number ranges represent a color that can be seen with the naked eye. Roast color has an impact on flavor and you might know, for example, that you really like medium-dark roasted coffee, coffee that has been roasted right before or just at second crack. If you know that, and you know that when a coffee has a whole bean Agtron reading between 50-40, then it is probably going to be more to your linking than a darker roasted coffee in the 40-35 range. To that end, reviews always include a translation from the numerical readings into terms most coffee drinkers understand – light, medium, medium-dark, dark and so on. If you’re interested in the breakdown of Agtron numbers and corresponding color terminology, see this table:

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