Michael Kay

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Which Ultra Violet Wavelength Do I Need?

Shortwave Ultra Violet

Shortwave UV 254nm - 266nm is used to check for the presence of phosphorescence.
Phosphor is used for postcode tagging dots and on the postage stamps of Great Britain from the 1960's onwards. Is also present on stamps from Canada (older issues), Finland, Greece, Israel, Mexico (older issues), USA.

Detecting the presence of phosphor:
Stamps must be removed from protective mounts and are best viewed against a dark background in subdued light, complete darkness is not normally required.
Please note that with phosphor you are looking for an afterglow as phosphor will absorb the light when you shine the light on the stamp and then re-emits it afterwards. On earlier Great Britain phosphors the afterglow is as follows:
20 seconds for BLUE, 10 seconds for GREEN and 5 seconds for VIOLET.

Shortwave UV can also be used to detect aniline inks, erased pen and fiscal cancellations, repairs to paper thins, added margins to imperforate stamps.

warning sign image WARNING! You must NEVER look directly into the light scource of shortwave ultra violet lamps as it is harmful to your eyes. Always remove batteries or unplug lamp when changing the tube. For this reason keep out of the reach of children.

Longwave Ultra Violet

Longwave UV 365nm - 380nm is use to check for the presence of fluorescence.
Fluorescence is used on the postage stamps of Great Britain from 1992 onwards, Australia, Canada, China, France, Germany, Hong Kong, Mexico, Norway, Russia.

Detecting the presence of fluorescence:
Stamps must be removed from protective mounts and are best viewed against a dark background in subdued light, complete darkness is not normally required.
With fluorescence there is a glow when you shine the light onto the stamp as it reflects the light.

Longwave UV can also be used to detect changes to inks, colours, forgeries, repairs and identify ACP, FCP, OCP, PCP papers. As well as check the authenticity of Artwork, Coins, Banknotes, Certificates, Credit Cards, Driving Licences, Passports, Phonecards, Postcards.