Card staining question
 

Hi, there. Was wondering what the term is for the type of staining shown here (not my cards, but the type of defect matches that on ones that I own). Brown/rust in color, not flat but actually a kind of raised bump on the cardboard surface. And is there a safe way to remove it? Thanks for any input.

For some reason I see that type of stain a lot on 1939 Play Ball.

Black mold spores. Lookup how they preserve old books to get an idea..?

That is interesting. Not sure I have heard that before. (which means very little)

I think the other term used for it is "foxing"? It is quite common in old books and other aged paper products.

Soak it in a little bleach and the mold will come right out.

Here, I have a solution for you:

https://www.seatoskyair.ca/wp-conten...s/image-7.jpeg

along with some paper too, especially in the future :). Who hasn't seen an old bleached card disintegrating?

not sure
 

but I seem to remember some bibliophile suggesting 15 seconds in a microwave. Attempt at your own risk :-)