soiling or discoloration of an object that cannot be easily removed because it is embedded in the substrate. Stains may be the result of uneven aging, foreign substances, chemical reactions, and improper handling.
Synonyms in English
splotch; smudge; smear; blotch; blemish; spot
For classification purposes, there are two basic types of stains: water-based and oil-based. Many stains are considered complex, consisting of a combination of water and oil components, particulates, and acids or bases. Typically, water-based stains require an acid mixture to counteract the acidity of the stain. Oil-based stains often require "dry cleaning" with non-aqueous chemicals. (Smithsonian Institution 2013)
For textiles, stains are sometimes pre-treated utilizing wet cleaning with water or mild solvents. Further treatment might include cleaning with a chemical enzyme designed to counteract the specific type of stain being addressed. Use of such chemicals may weaken fabrics, however, and individual assessment of fabric condition is necessary to determine if chemical treatment is appropriate. Textile cleaning treatments such as wet cleaning, may also cause stains when performed improperly. Bleeding and tide marks are two types of stains that may result from treatments. Contact with metal may also cause a chemical staining to occur. Metal fasteners or metal pieces woven into the fabric may cause staining that is unavoidable and irreversible. (Bachmann 1992)
Other mediums such as wood, marble, alabaster, etc. may become stained from prolonged exposure to moisture or light, acidic chemicals, adhesives, and improper handling.
Bachmann, Konstanze (ed.). 1992. Conservation Concerns: A Guide for Collections and Curators. Smithsonian books. ISBN 9787560981749.
J. Paul Getty Trust. 2004. Stains (damage). http://www.getty.edu/vow/AATFullDisplay?find=stain&logic=AND¬e=&english=N&prev_page=1&subjectid=300379497 (accessed 24 March 2014)
Matero, Frank G., Tagle, Alberto A. 1995. "Cleaning, Iron Stain Removal, and Surface Repair of Architectural Marble and Crystalline Limestone: The Metropolitan Club". JAIC 34 (1): 49-68. http://cool.conservation-us.org/jaic/articles/jaic34-01-004.html (accessed 21 March, 2014).
Stain Removal. 2013. Smithsonian Institution. http://www.si.edu/mci/english/learn_more/taking_care/stains.html (accessed 21 March, 2014).