Boutique coffee is classified according to sieve grade.

sieve classification

The method of sieve classification is the method of classifying coffee green beans according to their size. Raw beans are passed through a perforated iron sieve to determine the size of the beans and thus the grade. The size of the holes in the screen is 1/64 inch (less than 0.4mm), so the number of screens indicates that there are several 1/64 inches. For example, the size of No. 17 screen is 17/64 inches, which is about 6.75mm. Therefore, the larger the number of screens, the larger the particles of coffee beans. The reason for this classification is that larger beans sell better and produce more varied flavors than smaller beans. However, it is not that the beans with large particles must be of better quality than the beans with small particles. Ethiopian coffee beans are generally narrow and small, but their taste is the most unforgettable and favorite, including Yunnan's small coffee, which is highly evaluated in the international market. Kenya is one of the most representative countries classified by screen, others include Tanzania, Colombia, etc.(some countries use more than one classification method, and the examples given here are representative of countries dominated by this method). Kenya's highest AA++ requires a sieve of 18 or more, which means that the bean size exceeds 7.15mm. Kenyan beans are carefully graded to include AA++, AA+, AA, AB, etc. Colombia's classification is simpler, divided into Supremo and Excelso according to bean size. 80% of the special grade raw beans need to use more than 17 mesh screens, 80% of the upper grade raw beans need to use more than 14/16 mesh screens, and at most 11% of the 14 mesh beans are allowed in the 16 mesh beans. The screen mentioned above is for flat beans, round beans (Pea Berry) have their own set of screen size standards. The round beans are generally graded using a sieve of 8- 12.