What Causes "Fox Marks" on Old Books, Papers?

When you view old documents, frequently you see little bwonish splotches all over the pages. These marks are referred to as “fox marks”. What causes these marks? Are they a sign that the paper is decomposing?
And, can they be faked by forgers?

It’s caused by ferric oxide, which is possibly, but not proven to be fungal in origin. See page six for info.

I never heard of Fox Marks before, this is why I love this site. I don’t see a Wikipedia article about it. Someone needs to start one


There is. ‘Foxing’ is the more common term.

Somebody already did.

“Fair and balanced” investigative reporters? :smiley:

Heh. I though Fox marks would be “F”'s on all your political science papers. :smiley:

Seriously, it does appear that faking foxing is possible.

Yes they can be forged. I remember seeing a report of a forger who saw one of his pieces get appraised for a large sum of money on the “Antiques Roadshow”.

He went into detail on how he did the fox marks. Instant coffee and a slight misting of water from a spray bottle.

I don’t have a source other than memory, sorry.