Screen

A screen, in the rosin and sifting context, is a micron-rated mesh fabric — either sewn or ultrasonically welded into a filter bag for pressing, or stretched flat within a kief or sift box — that filters particulate plant material while allowing resin to pass through. Common materials are nylon monofilament (the most common choice, offering slight elasticity that resists blowouts), polyester monofilament, and stainless steel (used for durable kief-box screens). FDA food-grade nylon or polyester is required for any screen in direct contact with consumable product. Stitching standards include inside-out double-stitching for pressure tolerance and ultrasonic-welded seamless bags for shot-to-shot consistency. Rosin bag micron ratings are strongly standardized. 25 µm is used for premium hash rosin; 36–37 µm is the most common hash rosin choice; 45, 72–75, 90, and 115–120 µm step up for flower rosin, with 115–120 µm typically giving the best flower rosin yield; 160 µm is the maximum commonly used for flower filtration; and 190–220 µm bags are reserved for edibles-grade or minimally filtered runs. Critically, the micron number refers to the maximum particle diameter that can pass through the mesh opening, not the thread diameter of the weave. → See also: Rosin, Rosin press, Kief box, Dry sift