A rosin bag is a type of filter bag used in the rosin pressing process. These bags are typically made from a heat-resistant and durable material such as nylon or polyester mesh, and come in a variety of sizes to accommodate different amounts and types of plant material.
The bags are filled with plant material and then placed between the plates of a rosin press, where heat and pressure are applied to extract the resin. The mesh of the bag acts as a filter, allowing the liquid rosin to pass through while trapping plant material and other impurities.
Different micron size of the mesh is available to choose from to get different purity of rosin. They are usually reusable and can be cleaned after use to prepare them for the next pressing.