Ultraviolet light

An ultraviolet light, UV light, or black light is a useful tool for any collector.
 * Forgeries and reprints can be detected.
 * Alterations can be detected on stamps and covers.
 * It detects tagging and tagging types, as well as some paper varieties.

For tagging, you will need one that produces both longwave and shortwave light. The latter typically uses a filter and therefore the output is much dimmer. Results under each frequency range can be quite different. There are many devices that emit both types. When using shortwave for examining tagging, a separate shortwave device is recommended.

The ultraviolet tube does not last forever. You might prefer ones where suppliers also sell replacment tubes. In general, the cheaper the device, the shorter the tube life and the shortwave output will be dim.

There are many handheld devices that run off batteries. The lights are available through stamp supply houses and mineral collector supply companies. Stamp supply company-branded lights are rebranded devices made by others. You can pay somewhat less by buying the original but be aware that there are lookalike knockoffs that may be lesser quality.

Only idiots look directly into the lights. If you are hypersensitive to UV light, protective goggles are available. 



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