Foxing is an age-related process of deterioration that causes spots and browning on old paper

document A document is a written, drawn, presented, or memorialized representation of thought, often the manifestation of non-fictional, as well as fictional, content. The word originates from the Latin ''Documentum'', which denotes a "teaching" o ...

s such as

book A book is a medium for recording information in the form of writing or images, typically composed of many pages (made of papyrus, parchment, vellum, or paper) bound together and protected by a cover. The technical term for this phys ...

postage stamp A postage stamp is a small piece of paper issued by a post office, postal administration, or other authorized vendors to customers who pay postage (the cost involved in moving, insuring, or registering mail), who then affix the stamp to the ...

s, old

paper money A banknote—also called a bill (North American English), paper money, or simply a note—is a type of negotiable promissory note, made by a bank or other licensed authority, payable to the bearer on demand. Banknotes were originally issued ...

and

certificate Certificate may refer to: * Birth certificate * Marriage certificate * Death certificate * Gift certificate * Certificate of authenticity, a document or seal certifying the authenticity of something * Certificate of deposit, or CD, a financial pro ...

s. The name may derive from the

fox Foxes are small to medium-sized, omnivorous mammals belonging to several genera of the family Canidae. They have a flattened skull, upright, triangular ears, a pointed, slightly upturned snout, and a long bushy tail (or ''brush''). Twelv ...

-like reddish-brown color of the stains, or the

rust Rust is an iron oxide, a usually reddish-brown oxide formed by the reaction of iron and oxygen in the catalytic presence of water or air moisture. Rust consists of hydrous iron(III) oxides (Fe2O3·nH2O) and iron(III) oxide-hydroxide (FeO(OH), ...

chemical

ferric oxide Iron(III) oxide or ferric oxide is the inorganic compound with the formula Fe2O3. It is one of the three main oxides of iron, the other two being iron(II) oxide (FeO), which is rare; and iron(II,III) oxide (Fe3O4), which also occurs naturall ...

which may be involved. Paper so affected is said to be "foxed". Foxing is rarely found in

incunabula In the history of printing, an incunable or incunabulum (plural incunables or incunabula, respectively), is a book, pamphlet, or broadside that was printed in the earliest stages of printing in Europe, up to the year 1500. Incunabula were pro ...

, or books printed before 1501. Decrease in rag fibre quality may be a culprit; as demand for paper rose in later centuries, papermakers used less water and spent less time cleansing the rag fibres used to make paper. Although unsightly and a negative factor in the value of the paper item for collectors, foxing does not affect the actual integrity of the paper. Foxing also occurs in biological study skins or specimens, as an effect of chemical reactions or

mold A mold () or mould () is one of the structures certain fungi can form. The dust-like, colored appearance of molds is due to the formation of spores containing fungal secondary metabolites. The spores are the dispersal units of the fungi. Not ...

melanin Melanin (; from el, μέλας, melas, black, dark) is a broad term for a group of natural pigments found in most organisms. Eumelanin is produced through a multistage chemical process known as melanogenesis, where the oxidation of the amin ...

. Foxing can also be intentionally added to clothing to give it an aged appearance. Aside from foxing, other types of age-related paper deterioration include destruction of the

lignin Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and bark, because they lend rigidity ...

by sunlight and absorbed

atmospheric pollution Air pollution is the contamination of air due to the presence of substances in the atmosphere that are harmful to the health of humans and other living beings, or cause damage to the climate or to materials. There are many different typ ...

, typically causing the paper to become brown and crumble at the edges, and acid-related damage to cheap paper such as newsprint, which is manufactured without neutralizing acidic contaminants.

Causes of foxing

The causes of foxing are not well understood. One theory is that foxing is caused by a

fungal A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from ...

growth on the

paper Paper is a thin sheet material produced by mechanically or chemically processing cellulose fibres derived from wood, Textile, rags, poaceae, grasses or other vegetable sources in water, draining the water through fine mesh leaving the fibre e ...

. Another theory is that foxing is caused by the effect on certain

s of the

oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a ...

iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in ...

copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish ...

, or other substances in the pulp or rag from which the paper was made. It is possible that multiple factors are involved. High

humidity Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present. Humidity dep ...

may contribute to foxing.

Repairing foxed documents

Foxed documents can be repaired, with greater or lesser success, using

sodium borohydride Sodium borohydride, also known as sodium tetrahydridoborate and sodium tetrahydroborate, is an inorganic compound with the formula Na BH4. This white solid, usually encountered as an aqueous basic solution, is a reducing agent that finds applic ...

, proprietary bleaches, dilute

hydrogen peroxide Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscous than water. It is used as an oxidizer, bleaching agent, and antiseptic, usually as a dilute solution (3% ...

lasers A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The firs ...

. Each method risks side effects or damage to the paper or ink. Another method is to

scan Scan may refer to: Acronyms * Schedules for Clinical Assessment in Neuropsychiatry (SCAN), a psychiatric diagnostic tool developed by WHO * Shared Check Authorization Network (SCAN), a database of bad check writers and collection agency for bad ...

the image and process that image using a high-level

image processing An image is a visual representation of something. It can be two-dimensional, three-dimensional, or somehow otherwise feed into the visual system to convey information. An image can be an artifact, such as a photograph or other two-dimension ...

program. This can usually remove the effects of foxing while leaving text and images intact.

In biological specimens

It is generally not advisable to repair study specimens, except perhaps for mechanical damage.

Type specimen In biology, a type is a particular specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to anchor or centralizes the ...

s should – if at all possible – not be altered in any way. If foxing affects the study value of a specimen (e.g. in

bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...

or mammal skins or in

insects Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs ...

, where it might affect diagnostic coloration), this might rather be remarked on the specimen label. Color standards can provide a means of documenting coloration before or in the early stages of foxing.

Foxed clothing

Foxing may also be applied to clothing through intentional

scuffing Abrasion is the process of scuffing, scratching, wearing down, marring, or rubbing away. It can be intentionally imposed in a controlled process using an abrasive. Abrasion can be an undesirable effect of exposure to normal use or exposure to t ...

of shirt collars, cuffs and

shoes A shoe is an item of footwear intended to protect and comfort the Foot, human foot. They are often worn with a sock. Shoes are also used as an item of decoration and fashion. The design of shoes has varied enormously through time and from cult ...

, to make items of clothing appear older, used and well-worn.

References

* * Smithe, Frank B (1974): ''Naturalists' Color Guide Supplement''. American Museum of Natural History, NYC. . * Smithe, Frank B (1975): ''Naturalist's Color Guide'' (2nd ed.). American Museum of Natural History, NYC. . * Smithe, Frank B (1981): ''Naturalist's Color Guide Part III''. American Museum of Natural History, NYC. . *

External links