What is the difference between screen size 17 and 18 in coffee?
The difference between 17 and 18 refers to the physical diameter of the bean, measured in 1/64th of an inch. A 17 bean is 17/64 of an inch, while a 18 is 18/64. Larger beans, like size 18, are often associated with higher coffee quality and more uniform roasting, though size is only one factor in grading.
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In the coffee industry, grading is a vital process for ensuring consistency, and is one of the most common metrics used. The process involves passing beans through a series of perforated metal plates, or 'screens,' with holes of specific diameters. A of 17 means the bean is 17/64 of an inch in diameter, while a size 18 is 18/64. This simple measurement helps exporters and roasters categorize beans by size, which is a key indicator of quality and uniformity.
Why does size matter? Generally, larger beans are considered more desirable because they are often denser and have had more time to mature on the tree. When a batch of coffee is uniform in size, it roasts much more evenly. If you have a mix of very small and very large beans in the same batch, the smaller ones will roast faster and potentially burn, while the larger ones might remain under-developed. By sorting by , roasters can achieve a more consistent roast profile.
However, it is a common misconception that larger is always better. While size is a useful proxy for quality, it does not tell the whole story. A small bean from a high-, high-quality will almost always taste better than a large bean from a low-, commercial-grade crop. is just one piece of the puzzle, alongside factors like moisture content, defect count, and the specific of the coffee.
In many regions, specific screen sizes are tied to traditional grading standards. For example, in Colombia, the 'Supremo' grade is defined by a larger , typically 17 or 18, while 'Excelso' refers to slightly smaller beans. These labels help buyers understand what they are purchasing before they even cup the coffee. It provides a baseline for expectations regarding the bean's physical appearance and potential performance in the roaster.
For the reader, understanding helps demystify the labels on your coffee bag. If you see a reference to , you are looking at a standard of physical uniformity. While it is not a guarantee of flavor, it is a sign that the producer has invested time in sorting and grading their crop, which is usually a positive indicator of the care taken throughout the entire production process.
- ·https://sca.coffee/researchVerify source for reference 1 ↗
- ·https://www.ncausa.org/About-Coffee/10-Steps-from-Seed-to-CupVerify source for reference 2 ↗