# Foxing

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Age-related process of deterioration occurring on paper products

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For the music group, see [Foxing (band)](/source/Foxing_(band)).

Heavy foxing on the [title page](/source/Title_page) of an 1832 [textbook](/source/Textbook)

**Foxing** is an age-related process of deterioration that causes spots and browning on [paper](/source/Paper) [documents](/source/Document) such as [books](/source/Book), [postage stamps](/source/Postage_stamp), old [paper money](/source/Paper_money) and [certificates](https://en.wiktionary.org/wiki/certificate), and on textiles like clothing and artists' canvasses. The name may be a variant form of the English [West country](/source/West_country) dialect term *foust* and [Scots](/source/Scots_language) *foze*, to become moldy.[1] Alternatively, it may derive from the [fox](/source/Red_fox)-like reddish-brown color of the stains.[2] Paper that is affected is said to be "foxed".

Foxing is rarely found in [incunabula](/source/Incunable), or books printed before 1501.[3] Decrease in rag fibre quality may be a culprit. As demand for paper rose in later centuries, [papermakers](/source/Papermakers) did not use as much water and spent less time cleansing the rag fibres used to make paper.[4] An early work of art to have been affected by foxing is the *[Portrait of a Man in Red Chalk](/source/Portrait_of_a_Man_in_Red_Chalk)*, a drawing on paper by [Leonardo da Vinci](/source/Leonardo_da_Vinci).[5]

Foxing also occurs in biological study skins or [specimens](/source/Biological_specimen), as an effect of chemical reactions or [mold](/source/Mold_(fungus)) on [melanin](/source/Melanin). Textiles, such as articles of clothing, that are affected may also be said to be foxed.[6]

Aside from foxing, other types of age-related paper deterioration include destruction of the [lignin](/source/Lignin) by [sunlight](/source/Sunlight) and absorbed [atmospheric pollution](/source/Atmospheric_pollution), typically causing the paper to become brown and crumble at the edges, and [acid](/source/Acid)-related damage to cheap paper such as [newsprint](/source/Newsprint), which manufacturers make without [neutralizing acidic contaminants](/source/Acid-free_paper).[7]

## Causes of foxing

The causes of foxing are not well understood. One conjecture is that foxing is caused by a [fungal](/source/Fungal) growth on the paper.[8] Another is that foxing is caused by the effect on certain [papers](/source/Paper) of the [oxidation](/source/Oxidation) of [iron](/source/Iron), [copper](/source/Copper), or other substances in the [pulp](/source/Wood_pulp) or [rag](/source/Cloth) from which the paper was made.[9] It is possible that multiple factors are involved. High [humidity](/source/Humidity) may contribute to foxing.

## Repairing foxed documents

Foxed documents can be repaired, with greater or lesser success, using [sodium borohydride](/source/Sodium_borohydride),[10] proprietary [bleaches](/source/Bleach), dilute [hydrogen peroxide](/source/Hydrogen_peroxide) or [lasers](/source/Laser). Each method risks side effects or damage to the paper or [ink](/source/Ink).

Another method is to [scan](/source/Document_scanning) the image and process that image using a high-level [image processing](/source/Image_processing) program. This can usually remove the effects of foxing while leaving text and images intact.

Example showing yellowing of a black-and-white paper document over time. The document was printed by a print shop in year 1990 and was kept under normal non-smoking household conditions at all times. The image on the left was scanned in 2018, and on the right, in 2023. Both scans were made in full color.

## In biological specimens

It is generally not advised to repair study specimens, except perhaps for mechanical damage. [Type specimens](/source/Type_specimen) should – if at all possible – not be altered in any way. If foxing affects the study value of a specimen (e.g. in [bird](https://en.wikipedia.org/w/index.php?title=Bird_skin&action=edit&redlink=1) or mammal skins or in [insects](/source/Insect), where it may affect diagnostic coloration), this might rather be remarked on the specimen label. Color standards[11] can provide a means of documenting coloration before or in the early stages of foxing.

## See also

- [List of used book conditions](/source/List_of_used_book_conditions)

- [Distressing](/source/Distressing)

## References

1. **[^](#cite_ref-1)** Smythe Palmer, Abram (1890). ["Folk-Etymology: A Dictionary of Verbal Corruptions Or Words Perverted in Form Or Meaning, by False Derivation Or Mistaken Analogy"](https://books.google.com/books?id=7DIjAQAAIAAJ&dq=foxed&pg=PA128). *Google Books*. Retrieved 10 October 2024.

1. **[^](#cite_ref-2)** ["Foxing (PCC) – Wiki"](http://www.conservation-wiki.com/w/index.php?title=Foxing_(PCC)). *www.conservation-wiki.com*. [Archived](https://web.archive.org/web/20210109100752/http://www.conservation-wiki.com/w/index.php?title=Foxing_%28PCC%29) from the original on 9 January 2021. Retrieved 1 February 2018.

1. **[^](#cite_ref-3)** Iiams, Thomas M.; Beckwith, T. D. (October 1935). ["Notes on the Causes and Prevention of Foxing in Books"](https://www.jstor.org/stable/4302211). *The Library Quarterly*. **5** (4): 407–418. [doi](/source/Doi_(identifier)):[10.1086/613729](https://doi.org/10.1086%2F613729). [JSTOR](/source/JSTOR_(identifier)) [4302211](https://www.jstor.org/stable/4302211).

1. **[^](#cite_ref-4)** Dard, Hunter (1978). *Papermaking : the history and technique of an ancient craft*. New York: Dover. p. 154. [ISBN](/source/ISBN_(identifier)) [0-486-23619-6](https://en.wikipedia.org/wiki/Special:BookSources/0-486-23619-6).

1. **[^](#cite_ref-5)** Piñar, Guadalupe; Tafer, Hakim; Katja, Sterflinger & Flavia, Pinzari (2015). ["Amid the Possible Causes of a Very Famous Foxing: Molecular and Microscopic Insight into Leonardo da Vinci's Self-portrait"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4959533). *Environmental Microbiology Reports*. **7** (6): 849–859. [Bibcode](/source/Bibcode_(identifier)):[2015EnvMR...7..849P](https://ui.adsabs.harvard.edu/abs/2015EnvMR...7..849P). [doi](/source/Doi_(identifier)):[10.1111/1758-2229.12313](https://doi.org/10.1111%2F1758-2229.12313). [ISSN](/source/ISSN_(identifier)) [1758-2229](https://search.worldcat.org/issn/1758-2229). [PMC](/source/PMC_(identifier)) [4959533](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4959533). [PMID](/source/PMID_(identifier)) [26111623](https://pubmed.ncbi.nlm.nih.gov/26111623).

1. **[^](#cite_ref-6)** Mina, Laura (1 November 2019). ["Foxy Underpants: Or the Use of Chelators and Enzymes to Reduce Foxing Stains on Early Nineteenth Century Men's Linen Underpants"](https://www.tandfonline.com/doi/full/10.1080/01971360.2019.1674604). *Journal of the American Institute for Conservation*. **59**: 3–17. [doi](/source/Doi_(identifier)):[10.1080/01971360.2019.1674604](https://doi.org/10.1080%2F01971360.2019.1674604). Retrieved 10 October 2024.

1. **[^](#cite_ref-7)** ["The Deterioration and Preservation of Paper: Some Essential Facts – Collections Care – Resources (Preservation, Library of Congress)"](https://www.loc.gov/preservation/care/deterioratebrochure.html). *www.loc.gov*. [Archived](https://web.archive.org/web/20150120175215/http://www.loc.gov/preservation/care/deterioratebrochure.html) from the original on 2015-01-20. Retrieved 2020-11-25.

1. **[^](#cite_ref-8)** Arai, Hideo (October 2000). ["Foxing caused by Fungi: twenty-five years of study"](https://www.researchgate.net/publication/248436693). *Research Gate*. Retrieved November 24, 2020.

1. **[^](#cite_ref-9)** Kelsey, Marianne (21 January 2023). ["What Causes Foxing and Staining in Paper?"](https://kelseyconservation.com/what-causes-foxing-staining-in-paper/). *Kelsey Book and Paper Conservation*. Retrieved 10 October 2024.

1. **[^](#cite_ref-10)** Masters, Kristin. ["How to Prevent and Reverse Foxing in Rare Books"](https://blog.bookstellyouwhy.com/bid/230209/how-to-prevent-and-reverse-foxing-in-rare-books). [Archived](https://web.archive.org/web/20210109100754/https://blog.bookstellyouwhy.com/bid/230209/how-to-prevent-and-reverse-foxing-in-rare-books) from the original on 9 January 2021. Retrieved 1 February 2018.

1. **[^](#cite_ref-FOOTNOTESmithe1974_11-0)** [Smithe 1974](#CITEREFSmithe1974).

## Cited Sources

- Smithe, Frank B. (1974). [*Naturalist's Color Guide*](https://books.google.com/books?id=o6gXAQAAIAAJ). American Museum of Natural History. [ISBN](/source/ISBN_(identifier)) [978-0-913424-04-9](https://en.wikipedia.org/wiki/Special:BookSources/978-0-913424-04-9).

## Related Works

- Smithe, Frank B (1974): *Naturalists' Color Guide Supplement*. American Museum of Natural History, NYC. [ISBN](/source/ISBN_(identifier)) [0-913424-04-8](https://en.wikipedia.org/wiki/Special:BookSources/0-913424-04-8).

- Smithe, Frank B (1975-): *Naturalist's Color Guide*. American Museum of Natural History, NYC. [ISBN](/source/ISBN_(identifier)) [0-913424-03-X](https://en.wikipedia.org/wiki/Special:BookSources/0-913424-03-X).

- Smithe, Frank B (1981): *Naturalist's Color Guide Part III*. American Museum of Natural History, NYC. [ISBN](/source/ISBN_(identifier)) [0-913424-05-6](https://en.wikipedia.org/wiki/Special:BookSources/0-913424-05-6).

- Roberts, Matt; Etherington, Don (1981). [*Bookbinding and the Conservation of Books: A Dictionary of Descriptive Terminology*](https://books.google.com/books?id=iTU4rgEACAAJ). Washington, DC: Library of Congress. [ISBN](/source/ISBN_(identifier)) [978-0844403663](https://en.wikipedia.org/wiki/Special:BookSources/978-0844403663).

## External links

Wikimedia Commons has media related to [Foxing](https://commons.wikimedia.org/wiki/Category:Foxing).

- [The Library of Congress: 'Preserving Works on Paper'](https://www.loc.gov/preservation/care/paper.html)

- [Foxing](https://web.archive.org/web/20170704082955/http://mywingsbooks.com/coll-terms/fxt_.shtml)

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