2016-02-21

luminescence ...

Douglas Myall describes printer inks as flour-phosphor ... Royal Mail has a standard for value inks, but not for tagging inks.  Phosphor triggers the SWUV Royal Mail scanners - but no afterglow on forgeries...

"there is no fixed standard for fluorescence, `as it is used for security and quality assurance purposes only and does not have to follow strict operational facing requirements"  - Dr. A. R. Lane, the British Philatelic Bulletin,

multi-printings can show shades of value ink, and or shades of flour-phosphor inks.

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