Filter

A filter, in joint and spliff construction, is a small insert at the mouth end that serves as a mouthpiece, provides structural rigidity, and offers modest filtration. The term is used generically in the United States alongside crutch and tip; in the United Kingdom the equivalent component is usually called a roach. Materials include stiff paper or cardboard (the most common), glass, ceramic, wood, silicone, corn husk, and activated charcoal. Functionally, a filter prevents loose flower from being drawn into the mouth, keeps the paper cylinder open as it becomes moist, reduces finger and lip burns as the joint burns down, cools smoke slightly, and allows the user to smoke the full length of the roll. Effect on cannabinoid delivery varies by material. A 2001 inhalation study found that cigarette-style cellulose-acetate filters can trap up to roughly 30% of THC, while paper crutches and glass tips do not significantly absorb cannabinoids. Activated charcoal filters reduce tar and some carcinogens at the cost of some cannabinoid loss. Reduced perceived potency through simple paper crutches is usually attributable to restricted airflow rather than cannabinoid absorption. → See also: Crutch, Tip, Roach. ---