In the coffee world, numbers like '17/18' or '15' frequently appear in bean descriptions. These refer to the screen size, a fundamental aspect of coffee grading. While it might seem like a minor technical detail, for a roaster, screen size is a critical factor that directly impacts the final cup quality.
What is Screen Size?
Coffee screen sizes are measured in 64ths of an inch. A screen size of 18 means the bean is 18/64ths of an inch in diameter. Coffee is graded by shaking it through a series of perforated screens with different sized holes. The beans that are retained on a certain screen determine its size.
Why Uniformity is the Goal
The primary reason screen size matters is roast consistency. When you roast a batch of coffee, beans of different sizes and densities will roast at different rates. Smaller, less dense beans will roast faster than larger, denser ones. A batch with a wide variance in bean size will result in an uneven roast—some beans will be underdeveloped (sour notes), while others will be over-roasted (bitter, burnt notes).
By sourcing beans of a uniform screen size, such as Arabica AAA (Screen 18+) or AA (Screen 17), roasters can achieve a much more even and controlled roast. This allows them to consistently bring out the best, most complex flavors the coffee has to offer.
While size doesn't always equal flavor, it is an essential tool for achieving the consistency required for specialty coffee. That's why at VB Exports, screen size is a guaranteed specification for all our coffee grades.
