The way of sieve grading is to grade according to the size of raw coffee beans. The raw bean passes through the iron with holes.

Classification according to screen

The way of sieve grading is to grade according to the size of raw coffee beans. Raw beans are graded by determining the size of the beans through a holed iron plate sieve. The size of the hole in the screen is 1x64 inches (less than 0.4mm), so the size of the screen indicates that there are several 1x64 inches. For example, the size of screen 17 is 17x64 inches, which is about 6.75mm, so the larger the number of the screen, the bigger the particles of raw coffee beans. The reason for this grading is that beans with large grains sell better and are more likely to produce rich and varied flavors than small ones. But this is not to say that beans with large grains are of better quality than beans with small grains. Ethiopian coffee beans are generally narrow and small, but their taste is the most unforgettable and favorite, including Yunnan's small seed coffee. it is also highly appraised by the international market. Kenya is one of the most representative countries rated by sieve, along with Tanzania and Colombia (some countries use more than one classification, and the examples given here are representative, mainly in this way). Kenya's most advanced AA++ requires sieves larger than 18, that is, beans larger than 7.15 mm. Kenya beans are graded carefully, including AA++,AA+,AA,AB and so on. Colombia's classification is simpler, divided into Supremo (selected) and Excelso (upper) according to bean size. 80% of the raw beans of the selected grade need to use a sieve of more than 17, and 80% of the raw beans of the upper grade need a sieve of 14 and more than 16, and a maximum of 11% of the beans with sieve 16 are allowed to be mixed with 14 sieve beans. The screen mentioned above is for flat beans, round beans (Pea Berry) has its own set of screen size standards. Generally use the screen of 8Murray No. 12 to grade the round beans.