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 Post subject: Detecting phosphor bars on Wilding definitives
PostPosted: Sun Aug 05, 2018 3:58 pm 

Joined: Sat Feb 01, 2014 5:50 pm
Posts: 27
I am seeking information on how to detect and differentiate the three different phosphor bar inks on Wilding definitives. I have a Lighthouse UV source that I believe is “long wave” and a very old Raytech Industries Model BS-1 source, intended to reveal phosphorescent minerals in rockl samples and probably short and long wave (wavelengths unknown). I am not confident I have the right tools to correctly detect the three types. Any recommendations? Thanks.

 Post subject: Re: Detecting phosphor bars on Wilding definitives
PostPosted: Thu May 07, 2020 7:25 pm 
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Joined: Sun May 03, 2020 11:19 am
Posts: 107
Dear GbB,etc,
It would appear that your query posted back in 2018 has not been responded to before now even though you have had over 15000 views, which surprises me !

To identify the different types of phosphor bands applied to the multiple crown watermarked Wildings, you will need to radiate them with a shortwave ultraviolet lamp in the region of around 260 to 300nm for the best results in a dark environment, and observe the afterglow of the phosphor bands in question after the lamp has been switched off, in order to differentiate which type of phosphor it is.

There are basically three types, green, blue and violet, all of which have different decay times after excitation, blue being the longest of around 10 seconds, followed by the green phosphor of about 7 seconds, with the violet lasting for only around 2 to 3 seconds.

When checking for Wilding phosphors, make sure that you purchase a shortwave version and not the long wave one as this will only give you fluorescence in the embodiment of the stamps paper but is also useful for identifying chalk surfaced papers, such as the 3d Isle of Man stamp or stamps from the 2/- holiday booklet etc.

The shortwave lamp can be purchased from any reputable dealer of philatelic accessories, but you could possibly get it cheaper on eBay, the choice is yours !
A health warning usually comes with the packaging for you not to look directly into the light, as it could cause blindness.

Hoping that this information was of help, WM.
PS. Another interesting difference/feature I observed was that some of the phosphor bands had a matt finish, where others had a more glazed appearance, as with the following 6d and 10d+1/- values, all with 9½mm violet bands.
(673.7 KiB)
(614.18 KiB)
(470.44 KiB)

Could it be that a different type of phosphor was used ?
To add to the mystery here are some 7d values with similar features :-
(464.56 KiB)

Further investigation needs to be made of these variants, perhaps a viewer might/may have the answer ! WM.

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