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

ralph124c · June 30, 2009, 1:52pm

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?

silenus · June 30, 2009, 2:20pm

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

Markxxx · June 30, 2009, 3:26pm

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

nofloyd · June 30, 2009, 3:35pm

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

Hunter_Hawk · June 30, 2009, 3:35pm

Somebody already did.

Polycarp · June 30, 2009, 3:50pm

“Fair and balanced” investigative reporters?

Exapno_Mapcase · June 30, 2009, 3:58pm

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

Seriously, it does appear that faking foxing is possible.

Various devices are used to give a modern reproduction at least the superficial appearance of age. Tea or coffee are popular applications. One popular (and very cheap) series of John Speed maps was as brown as chestnut and, being on crinkled paper to give the supposed appearance of vellum, looked like overcooked poppadoms. In a message to Maphist on 13 December 2005, however, Daan Strebe described a more sophisticated attempt at deception (though without identifying the map involved):

“What caught my attention was the sudden revelation of typical and heavy aging. Yellowing. Mottling, particularly toward the edges. Foxing. Everything I would expect to see on a 400-year old map that had not been carefully preserved. Yet turning it away from the light, it reverts to its too-perfect condition. It is as if the map had been resurfaced somehow while somehow preserving the original image.”

MrTuffPaws · June 30, 2009, 7:33pm

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.