Warp (damage)

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Mechanical deterioration “caused by distortion, such as a bend or curve, in a rigid or semi-rigid material.”(CCI, 1994) A structural distortion of the support that has become twisted, turned or bent out of shape and is no longer flat or in plane. (The Fine Arts Conservancy, Glossary) 
==Related Terms==
Deformation,distortion, in-plane, planar distortion, bend, cradle
=== Synonyms in English ===
Deformation, distortion
=== Translation ===
English 	warp
French 	chaine
Spanish 	urdimbre
Portuguese 	urdidura
Italian 	ordito
German 	kette
Arabic 	انفتل
Chinese (Traditional)	變形
==Discussion==
Not to be confused with the definition of warp for textiles referring to "the longitudinal threads of a tapestry." (Lennard and Hayward, 2006)
Different kinds of warps include cupping, bowing, crook, longitudinal, transverse, and twist. Cupping for wood based objects refers to deformation across the width of an object. It is most often seen on wide, unsupported or unrestrained sections of wood. (NPS, 2002) For the purposes of the definition cupping is not to be confused with the concave flaking of paint layers, also known as cleavage. (National Services Te Paerangi, 2010) Bowing refers to a singe curved distortion to an object's flatness along its length. Crook is "the departure from end to end straightness along the edge" of an object. (Hoadley, 1995) Longitudinal warp occurs when the object distorts along its grain. Twist refers to warping where all "four corners of a flat face do not lie in the same plane." (Hoadley, 1995)
Warping can be caused by environmental changes, storage, and/or display conditions. Some common causes include inappropriate and/or rapidly changing relative humidity (RH) and temperature levels resulting in the expansion and contraction of organic materials such as cotton, wood, ivory, and paper leading to changes in size and/or shape different from the original or intended form of the object; restrictions due to inappropriate mounting and framing; and heat from a fire can cause extensive warping of objects made from inorganic materials such as stone, glass, metal, and ceramic. (CCI, 1993) (CCI, 1993)
Suggestions for reducing the warping of objects include:
* Avoiding "“tight framing or warping of the stretcher or backing board can cause an overall out-of-plane distortion of the canvas. This distortion may be reduced simply by improving the framing methodology.”(CCI, 1993)
* The use of cradling as one methodology for preventing warping of paintings on panel.(Buck, 2010)
* Use precautions to protect rigid support materials used with paintings such as ivory, wood, and card board during transit. Adequate space must be provided in the frame’s rabbet to permit the expansion of materials that swell in high humidity and minimize the risk of the support warping.(CCI, 1993)
* After a flood or water leak, properly drying water-damaged paintings can help prevent warping and paintings undergoing treatment should be monitored to identify warping.(CCI, 1997)
* Maintain stable temperature and humidity (RH) levels appropriate for the type of material. Relative humidity optimum ranges for paintings are 40-65%, paper 45-55%, photographic materials including film and negatives 30-40%, and wood, leather, textiles, and ivory 45-60%. (NPS, 1999) Temperature recommendations for exhibit space are 64-68 degrees Fahrenheit but not to exceed 75 degrees Fahrenheit (NPS, 1999) 
==References==
Canadian Conservation Center (CCI). Condition Reporting – Paintings.
Part III: Glossary of Terms – CCI Notes 10/11, 1994 http://www.cci-icc.gc.ca/publications/notes/10-11-eng.aspx
The Fine Arts Conservancy. Glossary.http://www.art-conservation.org/GLOSS_furn.html
Lennard, Frances and Hayward, Maria. “Tapestry Conservation: Principles and Practice” Routledge, 2006. http://books.google.com/books?id=CdOti2qTErcC&pg=PA242&lpg=PA242&dq=type+of+warp+transverse+conservation&source=bl&ots=4pUb7vlnia&sig=PmfSk6IWQlmhV-16goW3Mg9VKFU&hl=en&sa=X&ei=XPhWU8C8D8rLsAS6h4KACg&ved=0CFUQ6AEwBw#v=onepage&q=type%20of%20warp%20transverse%20conservation&f=false
National Park Service. Appendix N: Curatorial Care of Wooden Objects, NPS Museum Handbook, Part I. 2002. http://www.nps.gov/museum/publications/MHI/Appendix%20N.pdf
National Services Te Paerangi. 2010. Condition Reporting: He Rauemi Resource Guide 26. Museum of New Zealand Te Papa Tongarewa. http://www.tepapa.govt.nz/SiteCollectionDocuments/NationalServices/Resources/ResourceGuides/HeRauemiResourceGuide26ConditionReporting.pdf
Hoadley, R. Bruce. 1995. “Chemical and Physical Properties of Wood.” The Structural Conservation of Panel Paintings. Getty Conservation Institute. http://www.getty.edu/conservation/publications_resources/pdf_publications/pdf/panelpaintings1.pdf
Stewart, Deborah. Agent of Deterioration: Fire. CCI 2013 https://www.cci-icc.gc.ca/caringfor-prendresoindes/articles/10agents/chap04-eng.aspx
CCI. Care of Paintings on Ivory, Metal, and Glass – CCI Notes 10/14, part of CCI Notes Series 10 (Paintings and Polychrome Sculptures), 1993. [https://www.cci-icc.gc.ca/publications/notes/10-14-eng.aspx
CCI. Keying Out of Paintings - CCI Notes 10/9, part of CCI Notes Series 10 (Paintings and Polychrome Sculptures),1993 http://www.cci-icc.gc.ca/publications/notes/10-9-eng.aspx
Buck, Rebecca A. and Gilmore, Jean Allman. Museum Registration Methods 5th Edition. The AAM Press. Washington, DC. 2010.
CCI. Paintings: Considerations Prior to Travel – CCUI Notes 10/15, part of CCI Notes Series 10 (Paintings and Polychrome Sculptures) 1993. http://www.cci-icc.gc.ca/publications/notes/10-15-eng.aspx
CCI. Emergency Treatment of Water-Damaged Paintings on Canvas - CCI Notes 10/5, 1997. https://www.cci-icc.gc.ca/publications/notes/10-5-eng.aspx
National Park Service. 1999. NPS Museum Handbook, Part I. http://www.nps.gov/museum/publications/MHI/CHAPTER4.pdf
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