Fluorescent Ink And Paper In Classic Stamps

Hello,

I am no expert for fluorescent stamps and phosphor.
From what I understand both were used deliberately long after the classic period (for sorting purposes).

On the other hand, many stamps have very remarkable colors under UV light which one could call fluorescent as well (Michel gives those colors for German stamps for example). But it's more the ink than the paper.

What I would like to know is whether the paper was ever fluorescent in the classic era (before 1940), so very bright in UV light, or if a stamp is always bleached then or a forgery (modern paper)?

And if the paper is not fluorescent at all in the classic era, the ink was in opposite (as mentioned above, or also with the Eosin inks in Australia). Was in those cases where the ink is fluorescent, always only the ink fluorescent or also the paper?

No optical brightening agents in the paper pulp that gives a fluorescent reaction under UV before 1950!

I think someone posted this link in another thread but here it is again:
https://brixtonchrome.com/pages/und...nced-version
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The article above is mainly about stamps.Some old 19th century papers or prior can be flourescent
under a UV light because of certain discolorations due to particles of copper and iron that catalyze the oxidation of the cellulose,microscopic moulds form.Coatings applied on the surface of the paper for better inking; water stains are flourescent by nature...Dépends on what intensity of flourescence one is lookong for.
Flourescence is everywhere really.
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A summary of ultra-violet fluorescent materials relevant to Conservation :
https://aiccm.org.au/national-news/...conservation

thank you both. So my idea about the time before the 1950s was on the one hand correct, on the other hand things in stamp collecting are just always complicated :).

I was thinking about paper that really stands out (similar to the HB paper, but also in other countries than Canada), and if this can be a hint for bleaching or forgeries in classic stamps before 1940 or before 1900. perf12, do you have any experience with classic stamps and fluorescent paper, is this often the case (probably not), and if, it is probably more a dull fuorescence or only some fibers, not this really bright one? Are there any classic stamps or its varieties that are known for fluorescent paper and can even identified by it?

Classic stamp flourescence is not constant over time and is to variable.Just dipping a stamp in water will already change the flourescence under UV. That's why spectroscopic analysis is the only viable way of identifying old stamps.The known markers in the Genuine stamps permit detection of forgeries.This has been done for many countries already.
Below Italy:
https://www.spectroscopyeurope.com/...spectroscopy
India:
https://pdfs.semanticscholar.org/ad...4.1580905701

Thank you for the very interesting link. I will read and understand it hopefully when time is there. About the fluorescent paper in classic stamps: so my guess was probably correct that the fluorescence in classic stamps - if it is there - is not as bright and uniform as in modern stamps, but more cloudy and/or fibers? (And the other "fluorescent paper" would be the fluorescent ink that just goes trough the paper and so it appears the paper is fluorescent?)

Years ago during a like discussion , I was told some of the soaps like dishing washing soap and laundry soap will change or add to the fluorescent or glow under a light.

We could establish 3 main types of things that create flourescence in old stamps.
1) Different additives in the cellulose pulp during manufacture,and or coatings on the paper
after manufacture before printing.
2) Migration of oxydized particles from ink composition over the surface of the stamp over
time.In migration; a uniform flourescence of the entire stamp is not always the case.
It could just be localized with different glows from dark red (oxydized area) too blue
at some distance from it.
3) Changes over years due too washing with soap and other products as floortrader pointed
out.