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What is Foxing?

Felicia Dye
Felicia Dye

Foxing is a term that refers to rust-brown colored flaws on paper. The condition is commonly found on items produced in the 18th and 19th centuries. The exact cause of foxing is not known and methods of foxing restoration are subjects of debate. It is believed the problem is best managed by controlling humidity and contact.

A person may find vintage paper, including that used for documents, artwork, and maps, is prone to developing fox spots. When this happens, the item is said to be foxed. The reason why these spots appear and the cause of these spots are not conclusive.

Foxing is rust-brown spots that develop on old paper.
Foxing is rust-brown spots that develop on old paper.

Speculation, however, attributes the problem to interactions between fungi and iron salts, or ferrous oxide, in the paper. Fungi spores are small and can easily travel through the air. Foxing often begins at edges of pages and moves inward. For many, this suggests that environmental factors indeed play a significant role in the problem. It is also believed that acidic materials, such as cardboard and glues that come into contact with an item, can aggravate foxing.

The condition can generally be controlled if relative humidity is controlled. A certain degree of relative humidity is needed for the growth of fungi. Therefore, it is recommended that items that are foxed or those which are likely to become foxed should be stored in a place where the relative humidity is below 70 percent. When this happens, the fungi should become dormant. It should be noted, however, if the document is taken out of this controlled environment, the fungi is likely to begin growing again.

There are a number of ways foxing restoration may be done. The effects of the spots may be reduced with sodium borohydride or calcium hypochlorite. Some people have found that repeatedly dabbing hydrogen peroxide onto the spots eliminates them. The debate over foxing restoration stems from the problems that can be associated with each method. Attempting to correct fox spots often damages the quality of the paper, jeopardizes the artwork or printed content, or only works short term while causing more problems in the long term.

As there is debate with regards to foxing restoration, there are also debates over the necessity of such a process. Many people attempt to remove fox spots to maintain or increase the value of items such as old books or artwork. Some, however, feel that like other antiques, the flaws should not be a factor that diminishes value.

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Discussion Comments


There are two pawn shops in my town that specialize in antiques. I have friends who work at both of them, and they have different opinions regarding foxing.

One shop sees it as a mark of antiquity. They will readily pay a good price for documents and original editions of books with foxing on the pages, as well as works of art that have fox spots.

The other shop holds that items with foxing have lost value, because they were not kept in mint condition. They only buy items that closely resemble the state they were in when they were new.


It is amazing that foxing can disappear and reappear like that. I would think that if fungi dried out, they would die. It’s kind of creepy that they can live invisible in plain sight and we can’t even tell they are there until the humidity rises.

My friend has her great-grandmother’s old diary with foxing on the pages. I came over one day while she was applying hydrogen peroxide to them with a cotton swab. Neither of us knew that fungi were to blame, and I think if we had, we wouldn’t have touched it so readily.

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    • Foxing is rust-brown spots that develop on old paper.
      By: Dmytro Sukharevskyy
      Foxing is rust-brown spots that develop on old paper.