Wilding Regionals

Until the late 1990s, all phosphor used reacted to short-wave uv-light. From the late 1990s some also reacted to long-wave uv-light. There are three types (for the Wildings): green, blue and violet. Scotland regionals occur with both blue and violet phosphor. The violet phosphor on Wildings stamps can be 8 mm wide or 9½ mm wide.

There are no Wildings printed on fluorescent paper; i.e., no fluorescent coating was used for the Wilding stamps, including the regionals. Fluorescence does occur. This was caused by optical brightening agents with which the rags used to produce the paper had been treated. This, however, is unintentional fluorescence.

I am not quite sure how that would occur. Fluorescence tends to be a reaction where the paper and especially the unprinted part becomes brighter under long-wave uv-light. The reaction disappears when you turn off the lamp. On Wilding stamps, phosphor tagging always comes in bars that react to short-wave uv-light. When you turn off the lamp you get Christmas lights on Oxford Street.



top: violet phosphor
bottom: blue phosphor.

I should ask a surgeon to take such pics.

I find the violet afterglow disappears very quickly. The blue and green ones last longer. Most phosphor Wildings exist with 8mm blue phosphor and 8mm and 9½ mm violet phosphor bars. It could have something to do with that. Sometimes you can look at the back of the stamps as typography and flexography can use enough pressure to show some embossing effect on the back.

On Machins, they continued with the violet phosphor. They, later introduced another version of it. On Machins, however, the bars tend to be easily visible with the naked eye when held at angle to the light. This is less the case with the revised violet phosphor of the 1980s. Of course ACP and PCP do not have bars. So they require a uv-lamp.