Strange Stamp Backings

I have noticed after some detective work that many stamps have different backs. I mean by this some stamp backs are clean white ( the sort you would find after soaking them of paper). Then I found stamps with a shinier back which had the appearance of being glazed. I have never found anything like this in my collection before and I wonder if you could help me work out what this is and what it is done for.

P.S:I have also noticed this with the same stamp one has a glazed appearance and one is not.





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Hi Bailoo. You question is not easy to answer, because there are many reasons. Maybe if you are more precise and give us some examples? For one, a glazed look could mean shiny gum - some stamps that I collect come with more than one type of gum

Peter

Thank you Peter

My stamps are shiny looking land they have dust trapped in them behind the gum, giving it a sort of glazed appearance.

From what I can see, it looks like the top one has gum and the bottom one does not. Some gums are darker and more yellowish in color and the newer PVA gums are more translucent. Some shiny and some not so much.

If the top one was moistened and stuck on an envelope but came off easily the remaining gum could contain foreign matter, or it may be a full gum stamp which was cancelled to order. Most CTO stamps come with full undisturbed gum, but sometime they are cancelled and have the gum removed.

You cannot see the shine in the picture. If it was taken at an angle it may be more visable. Either way, they are cancelled and are considered used and the gum is really irrelevant.

Agreed,
this what you are seeing, a clean stamp with gum removed, and a cancelled stamp with full, light yellow gum.
Very common with 1960's -1980's Czechoslovakia.