Sunday, 11 February 2007

Detecting Phosphors & UV Lamps

Pete Raymond recently wrote to me and asked about UV Lamps. Thanks Pete, I will see if I can answer your questions in plain English as this is a difficult subject to write about.

What is a UV lamp?

What is the best type to purchase ?

Where can I obtain one?

Ultra Violet Lamps are an essential piece of equipment for serious philatelists, especially if you are serious about collecting Machins. Two of the main functions are to identify phosphor bands (both fluorescence, colour, phosphor type ) including degrees of phosphor application and after glow.

These are also an aid to deducing short and inset bands.

A secondary use is determining the paper types, : OCP, FCP, PCP, ACP etc, ( essential on later De la Rue Byfleet & Dunstable printings which through changes in paper suppliers during the earlier printings have various degrees of OBA in the paper makeup. (bright, intermediate and dull).

There are many types of UV on the market, manufactured by different makers and they come in an array of price bands.

The Machin collector will need at least two, a short wave and a long wave. Most specialists including my self have Four.

Two desk lamps, which I use in my home or office ( one short one long wave) run from mains electricty. These are ideal for home use as one can use them hands free enabling the user to combine a magnifier or microscope.

below is a desk lamp with a magnifier incorporated into the hood.

I have two portable battery hand held lamps, again one short wave and one long wave. I pop these into my bag when visiting shows, stamp shops and post offices. I have found many a bargain purchased at face value at the post office, and one or two at shows which have paid for these portable lamps ten fold.

Long wave, is for detection of fluorescence of stamps and phosphors which ranges over a Broad spectrum of long waves giving Peak efficiency at 366 nm and a reliable detection of luminescence.

Below is a image of a portable lamp.

They ( long wave ) are suitable for use on most areas with A or C phosphor. i.e. Canada, Mexico, Norway, France, Hong Kong, People’s Republic of China, Russia and Machin definitives of Great Britain after 1992.

Short wave: Ultra Violet (UV) lamps are used for the detection of phosphorescence on earlier stamps with B phosphor pre 1993 .

Short wave UV light gives Peak radiation efficiency at 254 nmFor assured phosphorescence detection of stamps from Great Britain, USA, Israel, Finland and older issues from Canada and Mexico.

It should be noted when using short wave lamps the user should not look directly into the light. To do so over a prolonged period so can be detrimental to ones eye sight.

Prices for hand battery held Long wave are usually in the range of £7 - £12 and for short wave £20 - £30.

Tip: place a peice of clear glass over your stamp to convert long wave light into short wave

Desk lamps are available from £10 - £25 for long wave and £ 30 - £45 for short wave.

These are available from most stamp dealers or you can pick them up direct from wholesalers(prinz or lighthouse) via the Internet.

If you have problems aquiring one let me know I can send you a scan of the product and price. ( postage & packing will apply)

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