Foxing is the result of both mold and metal contaminants in paper. Foxing appears as brown, yellow, or red stains on the paper, often in spidery spots or blotches.
Synonyms in English
foxmarks; fox spots; spotting
|French||rousseur; piqûre; taches de jaunissement|
|Spanish||manchas rojizas de humedad|
|Portuguese||mancha de humidade|
|Italian||macchie di ruggine|
|Dutch||bruine vlekken; roestvlekken|
|Swedish||fuktfläck; mögelfläck; foxing|
High humidity and damp conditions are the main causes of foxing. Due to the metal in papermaking machines, iron in the water source, dirt or pollution, there may be traces of metal dispersed among the paper fibers. When the paper absorbs moisture, the metal traces begin to oxidize in those areas, causing disintegration and discoloration. This creates an acidic environment, which also encourages mold growth. Mold will also feed on the paper itself as well as any organic materials on the paper such as dirt, finger marks, food stains, or insects.
To prevent foxing, proper storage is necessary. Paper materials should be kept in a cool, dry, clean room with minimal exposure to light. Avoid environments where temperature and humidity can fluctuate, such as basements, attics, areas near radiators and vents, and areas prone to flooding. Store paper materials in protective enclosures, such as acid/lignin-free folders and polyester sleeves, separate from other acidic papers to prevent acids from migrating. A conservator may be able to minimize foxing stains by bleaching the paper then de-acidifying afterwards, however there is no guarantee that this will eliminate the foxing altogether and there is risk that this treatment can alter the tonal qualities of some pigments.
It is important to maintain proper storage even after conservator treatments, as fox spots can reappear when exposed to humidity.
The Paper Conservation Wiki includes a more detailed page about foxing.
Architecture.com from the Royal Institute of British Architects. “Palladio and Britain.” Accessed March 20, 2014. http://www.architecture.com/librarydrawingsandphotographs/palladio/exhibitingpalladio/thedrawinglaboratory/casestudies/palazzovalmarana/foxingxvii4.aspx
CAMEO:Conservation and Art Material Encyclopedia Online. “Foxing.” Accessed March 20, 2014. http://cameo.mfa.org/wiki/Foxing
Getty Research Institute. “Foxing.” Accessed March 20, 2014. http://www.getty.edu/research/tools/vocabularies/aat/
Library of Congress. “Care, Handling, and Storage of Works on Paper.” Accessed March 20, 2014. http://www.loc.gov/preservation/care/paper.html
Victoria and Albert Museum. “Caring for Your Books & Papers.” Accessed March 20, 2014. http://www.vam.ac.uk/content/articles/c/caring-for-your-books-and-papers/
International Federation of Library Associations and Institutions. "Multilingual Glossary for Art Librarians." Accessed March 17, 2016. http://archive.ifla.org/VII/s30/pub/mg1.pdf
NEDCC Preservation Leaflets. "Conservation Treatment for Works of Art and Unbound Artifacts on Paper." Accessed March 18, 2016. https://www.nedcc.org/free-resources/preservation-leaflets/7.-conservation-procedures/7.5-conservation-treatment-for-works-of-art-and-unbound-artifacts-on-paper