page_title: Blacklight
section_title: Incandescent
hierarchical_section_title: Blacklight / Types / Incandescent
caption_attribution_description: English: A 100 watt "black light" ultraviolet light bulb. This is an incandescent bulb with a coating on the glass which selectively absorbs visible light and passes ultraviolet. Since only a tiny fraction (0.1%) of the light emitted by the filament is ultraviolet, most of the light is absorbed by the coating, so the bulb gets very hot, and has a short lifetime. Because of differences between the UV response of the camera sensor and the human eye, the camera failed to capture the color of the bulb quite accurately; the filament actually appears magenta, not white.
context_page_description: A blacklight, also referred to as a UV-A light, Wood's lamp, or ultraviolet light, is a lamp that emits long-wave ultraviolet light and very little visible light.
  One type of lamp has a violet filter material, either on the bulb or in a separate glass filter in the lamp housing, which blocks most visible light and allows through UV, so the lamp has a dim violet glow when operating. Blacklight lamps which have this filter have a lighting industry designation that includes the letters "BL". This stands for "blacklight".
  A second type of lamp produces ultraviolet but does not have the filter material, so it produces more visible light and has a blue color when operating. These tubes are made for use in "bug zapper" insect traps, and are identified by the industry designation "BLB". This stands for "blacklight blue".
  Blacklight sources may be specially designed fluorescent lamps, mercury-vapor lamps, light-emitting diodes, lasers, or incandescent lamps; although incandescents produce almost no blacklight, and so are not considered true blacklight sources.
context_section_description: A black light may also be formed by simply using a UV filter coating such as Wood's glass on the envelope of a common incandescent bulb. This was the method that was used to create the very first black light sources. Although incandescent black light bulbs are a cheaper alternative to fluorescent tubes, they are exceptionally inefficient at producing UV light since most of the light emitted by the filament is visible light which must be blocked. Due to its black body spectrum, an incandescent light radiates less than 0.1% of its energy as UV light. Incandescent UV bulbs, due to the necessary absorption of the visible light, become very hot during use. This heat is, in fact, encouraged in such bulbs, since a hotter filament increases the proportion of UVA in the black-body radiation emitted. This high running-temperature drastically reduces the life of the lamp, however, from a typical 1000 hours to around 100 hours.
caption: 100-watt incandescent black light bulb
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