blacklights

Blacklights are a type of lamp that emits ultraviolet A (UV-A) radiation with little visible light. They are designed so that most of the light released is in the long-wave end of the ultraviolet spectrum, typically around 365–370 nanometers, which causes certain materials to fluoresce. Because visible light output is minimized, the lamp itself often appears dim and has a characteristic purplish glow in use.

How they work: Blacklights can be based on mercury-vapor lamps, fluorescent tubes with UV-emitting phosphors, compact fluorescent designs, or UV-emitting LEDs. The emitted ultraviolet photons excite fluorescent substances present in many objects, pigments, and minerals. The visible light output is filtered or reduced, so the lamp is perceived as dark while the fluorescence becomes visible against the surrounding environment.

Types and sources: Traditional glass tubes and older incandescent designs used filters to block most visible light. Modern variants include UV-A LEDs, as well as fluorescent and mercury-free options. Some lamps are marketed specifically as “blacklight” or “UV-A” sources and are chosen for their stronger fluorescence effects or more energy-efficient operation.

Uses: Blacklights are widely used in entertainment and art settings to create glow effects, and in forensics and authentication to reveal fluorescent features on papers, currencies, and dyes. They are also used in mineralogy to identify fluorescent minerals, in insect traps to attract certain pests, and in dermatology with Wood’s lamp examination of skin conditions. The effectiveness depends on the presence of fluorescent materials.

Safety: UV-A radiation can cause eye and skin damage with prolonged exposure. Use shielding, avoid direct eye exposure, and limit personal exposure, especially for children and sensitive individuals. Proper ventilation and caution with materials that may heat or emit fumes are advisable.