A black light is similar to a traditional florescent bulb. However, there are a few important differences. A black light creates light by sending a current of electricity through a tube with mercury and inert gas sealed inside it.

The outside of the tube is coated with phosphor. When power is applied to the tube, the mercury produces a number of different light photons which are produced primarily in the ultraviolet wavelength. These photons react with the phosphor and the resulting black light is created.

It all sounds pretty scientific because it is; there is actually a chemical reaction-taking place at the atomic level. Pretty cool stuff huh?

There are many different uses for black lights, including the traditional party black lights, which can include strobe effect and various colors to produce an almost hypnotic effect.

There are a number of other unique uses of the black light. The first is to cause a reaction to a poster or other printed material that is fluorescent. A fluorescent object will continue to glow as long as the black light is on and placed near the object.

A number of groups use black lights to identify or verify certain items. Did you know the US government uses specially designed black lights to identify counterfeit money? The secret is that in larger bills the US mint has included a florescent strip which cannot be copied or duplicated using a scanner or upper end copier. Next time you change a large bill at the bank watch the tellers. They will probably check it by scanning the bill with a black light.

Your local heating and cooling repairman also uses black lights to find leaks in your air conditioning system. This is accomplished by injecting fluorescent dye into the refrigerant and shining the black light on all the connections. When they spot a section that is glowing they know they have your leak.

One final word concerning black lights - they can be fun and useful but also dangerous. Never stare at a black light or remained exposed to one for more then a few hours at a time.