Micron grade refers to the fineness of a mesh screen, also called a micron screen, that is used to make ice water hash, aka bubble hash. A variety of micron-grade mesh screens are used to filter the different sizes of trichome heads from contaminated plant matter. It’s all about the size of the heads on the trichomes, which can vary like fruit on a tree.
Common micron-grade screens used for hash making are 73, 90, and 140 microns for high-quality hash. With different micron screens, you can filter the hash for the best possible separation of trichomes for full melts with less contaminated plant matter.