UVA lamps made with "Woods Glass" to filter out most visible light whilst allowing the UVA to pass through. The lamps have a variety of uses from counterfeit detection to non-destructive testing and special effects.
Blacklight Blue lamps are UVA lamps with a woods glass envelope. This envelope is a dark blue colour and it designed to block as much of the visible spectrum of light as possible whilst allowing UVA to pass. This way the UV light will not be overwhelmed by visible light. This is beaause some phosphoes will change the wavelength of UV light from the invisible UV spectrum to the visibe light spectrum. This makes these lights particulally useful in a number of applications.
Blacklight Blue lamps (BLB) are use in a number of applications the most obvious one being security marking, viewing a credit card, passport or bank note under these light will reveal security measures to enable them to be validated as genuine.
The other most popular use is for partys or disco's and theatres where the lights are uses to make scenes or clothing fluoresce including activating special glow inthe dark paints.
These lamps are sometimes used in non-destructive testing in conjunction with a fine powder to identify stress cracks in structures or planes for example.