Blacklight Fun

A place for fun, learning, and exploration in the world of electricity and its technologies

Blacklight Fun

Of all the cool things that can be done with lighting, blacklight effects are probably the most fun! Its eerie and mysterious look can really stimulate your imagination, and help you design that hippie room, haunted house, or anything else you can think of.

The best place to start in understanding blacklight technology is with the electromagnetic spectrum, and that part of it that the human eye responds to. Although

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blacklight lamps appear to be a dark purple, the actual radiated energy that causes the effects you see is outside the visible spectrum and cannot be seen directly. The visible purple light represents the inefficiency of the lamp and is wasted energy - although it does look cool! The typical human eye responds to electromagnetic energy between 400 & 700 nanometers. Below this range is ultraviolet, x-ray, and gamma ray energy. Above this range is infrared, microwave, and radio wave energy. The blacklight energy that causes the fluorescent glow of certain materials lies within the range of 320 & 400 nanometers in wavelength.

400 watt mercury vapor blacklight source with filtered glass bulb

The least expensive blacklight source is an incandescent lamp with a filter coating over the bulb. These are also the poorest types however, because the filament emits only about 1 to 2 percent of its energy in the effective region

comparison between a 13 watt compact fluorescent blacklight and a 75 watt incandescent type against reactive material

below 400 nanometers. It won't have much effect on your poster, and because the filtered glass absorbs most of the other 98 or so percent of the radiant energy they get extremely hot! The best and most popular blacklight sources are fluorescent lamps with a special phosphor that is optimized for energy output between 320 & 400 nanometers, and a filtering glass to eliminate most of the visible light. These come in many shapes and sizes now, both as a tubular type that operates in a ballasted fixture, and a compact type which has an integral electronic ballast and uses a standard screw base socket. The compact fluorescent type is becoming popular, is also relatively inexpensive, and a superior source to the incandescent lamp in terms of both efficiency and effectiveness. The commercial entertainment industry often uses higher powered mercury vapor lamps (such as the one shown) with either a filtering glass bulb or fixture lens. These typically come in sizes of 400 or 1,000 watts, and are useful for large display areas such as performance stages or haunted house attractions.

So how does light that we can't see show up as bright colors that we can? Blacklight posters,

fluorescent ink
poster

phosphorescent
materials

paints, and glow-in-the-dark ghosts and skeletons all use materials which are called blacklight-reactive. These work by absorbing photons with a short wavelength (in the <400nm ultraviolet range) and emitting photons in exchange with a longer wavelength that is visible to us - such as green, yellow, or red. These blacklight-reactive materials fall into two categories: fluorescent and phosphorescent. Fluorescent paints, inks, or dyes glow only as long as they are energized by ultraviolet light. Phosphorescent materials will absorb and store this ultraviolet energy and continue to glow for a period of time after the ultraviolet energy is removed. An example of this would be glow-in-the-dark hands on an alarm clock that can be seen after the room lights are turned off.

Black Light Stage Effects