Cancellation / Postmark Ink

Thanks for your post, Linda.

I am surprised to hear that a web search did not get you any good results, because when I did one for "postmark ink composition", I got the following:
I imagine that this is correct for postmarks, because in the early days, the postmarks could be cleaned off the stamps by using solvents like acetone or benzene.  Some philatelic writers, like Stevenson, have even suggested that hydrogen peroxide could be used to remove a postmark and leave the stamp intact.

It was more often the stamps that were printed with the pigment-based inks, I think.  At least it was the case with the Cape of Good Hope triangles from 1853-1864.

Hope this helps a little.

Linda, I am glad if I helped.

In truth, I don't know that much in general about the inks used for postmarks and stamps, but I have learned a little in my study of the Cape Triangles.  As it happens, the British Post Office was so concerned about fraudulent re-use of stamps by removing the cancels, that Perkins Bacon, original printers of the Penny Black and later the Cape Triangles, added a mineral ingredient to the stamp ink so that if the stamp was treated with a solvent like acetone, the design of the stamp would be affected.

Interestingly, it was the adding of this ingredient (a derivative of prussiate of potash, which is a compound containing ferrocyanide), that turned the paper blue during the printing process of the stamps.  That is why stamps from early GB, Cape of Good Hope, and others printed with these kinds of inks have blued paper.  There has been a lot of discussion about the blued paper in the COGH thread, if you want to read more about it.

So, even though I never set out to learn about stamp or postmark inks, I have picked up some tidbits along the way.

It depends on the country and the era.