transparencies

Transparencies are clear, light-transmitting materials or printed images designed to be projected onto a screen. The term commonly refers to two formats: overhead transparencies, which are sheets of clear plastic used with overhead projectors, and 35 millimeter slide transparencies, used with slide projectors.

Substrates for transparencies are typically clear polyester or cellulose acetate, sometimes polycarbonate, with thickness around 0.1 millimeters. Images may be produced by inkjet or laser printers on transparency film, or by traditional photographic processes that create a positive image on a transparent base.

Overhead transparencies carry text, diagrams, or photographs that are illuminated from behind by a projector, allowing a presenter to display material to an audience. Slide transparencies carry a single image inside a frame and are viewed by light passing through the film inside a slide projector.

In modern usage, digital projectors and screens have largely replaced transparency-based presentation methods in classrooms and meeting rooms, though transparencies remain in some archival, artistic, or specialized industrial contexts. Caring for transparencies involves protecting them from scratches, heat, and UV exposure; they are best stored in sleeves and cleaned with a soft, lint-free cloth.