Quote:
APparently Winnipeg tagging is much less visible, being fluorescent instead of phosphor
Correction here - the Winnipeg tagging is the phosphorescent type.
Fluorescent tagging will glow only when the UV light is shining on it - as soon as the UV light is turned off, the tag stops glowing. Phosphorescent (Winnipeg) tagging has an afterglow that lasts a few seconds, and it's most easily seen in a completely darkened room. I have a guest bathroom that has no windows and that has become my UV room (I don't have any guests but I have a lot of tagged stamps!). Turn off the lights and shut the door and it's almost completely dark inside, and it's easy to spot phosphorescent tagging that way. I run the light over the stamps with my eyes closed, and then I turn off the lamp and open my eyes - the stamps with Winnipeg tagging jump out at me then.
Winnipeg tagging is somewhat susceptible to soaking - used stamps are often more difficult to identify than mint ones. I find this to especially be the case with British stamps, which use the same type of phosphorescent tagging method as the Winnipeg tagged stamps. OP2 tagging doesn't seem to care how long you soak it, it stays bright under UV light.
I'm sure there are storage considerations for all types of tagging, but I'm also sure there are unequal amounts of phosphorescent / fluorescent material in tagging. Some mint stamps can have extremely bright tagging whereas others are much less vivid.
OP4 tagging, the migrating stuff, is a bit odd in that it doesn't seem to be the same from one issue to another. Some of the high value Landscape definitives (like the 25c polar bears) from the early '70s have very faint OP4 tagging. Some stamps, like the 1972 8c World Health Day commemorative, can have very bright tagging. Colour can vary somewhat, and I don't yet have a good sense of what kind of tagging is what, because sometimes the OP4 can look almost exactly like the OP2.
The Health Day stamp is a good issue to look at (on mint stamps especially) when trying to understand the possible problems - you can often see tagging "soaking through" to the back of the stamp. Here's a photo of a horrible example, some OP4 stamps I got once in a glassine - everything glows to some degree, the front of the stamps, the back of the stamps (I've turned a couple over), the glassine envelope, probably the spot on the table where I've set the envelope ....
The stamps turned over are the Health Day stamps, and you can see the design of the 1972 Frontenac stamps (also with migrating OP4 tagging), which look pretty much the same on the back side. I've also attached a shot of a couple of different Health Day stamps turned over, which obviously show different levels of problems with tagging migration.
Ryan
Posted 12/06/2012 9:04 pm
