Contributions by: Will Sassorossi
Patina (Noun): An aged appearance caused by environmental factors, either acquired naturally or artificially induced. Used with regard to a surface layer on metal caused by oxidation or corrosion (Art and Architecture online, 2004). Can be green or black in color on certain metals like copper and bronze (Merriam-Webster online, 2013). A condition or effect.
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Patina will be found mostly on metal objects, especially those made of copper, brass and silver. It is a form of corrosion that can have deleterious effects on these objects but also can enhance aesthetics of the objects. Patina will cover an object in a fine layer and could be considered to have film like qualities to the touch and appearance. It will cover the original layer of metal and depending on the metal type, will exhibit different colors. The color that has now replaced the original color of the metal may, depending on the individual, be more desirable and pleasing to the eye.
The formation of patina on copper or bronze objects is a result of the natural process of oxidation of the metal. This is due to weather conditions and the aging process of metal itself, depending on the environment and the resulting color may provide a pleasing look. A patina layer on silver objects, however, may need to be removed in order to display the value of the silver, but this must be done carefully. In many instances, silver may be a plating on top of an alloyed base layer of metal and by polishing the silver layer, the patina may be removed. This must be done carefully because multiple cleanings actually strip away the silver and over cleaning might severely damage the silver layer (Long, 1999).
Objects recovered from a maritime environment will require different cleaning techniques in order to keep or remove a patina layer, as well as removing enough of the salts that have penetrated the inner layers of the object. These salts, or chlorides, have a more deleterious effect on the object itself, rather than the patina. Depending on the object, the treatment options are, ìdirected to finding ways of curing the affected areas while retaining the rest of the patina unaltered,î (North, 1987). Each object must be evaluated on a case by case basis to determine the effects of either leaving the patina or to remove it to uncover the original metal finish.
References[edit | edit source]
Anonymous, 2004.Patina. Art and Architecture Thesaurus Online. Los Angeles, CA: J. Paul Getty Trust. , Accessed April 5, 2013.
Anonymous, 2013. Patina. Merriam-Webster Dictionary Online. Springfield, MA: Merriam-Webster Inc. , Accessed April 5, 2013.
Long, Deborah, 1999. Caring for Silver and Copper Alloy Objects. National Parks Service, Washington, DC. , Accessed April 11, 2013.
North, N.A., Macleod, I.D., 1987. Chapter 10.4: Corrosion of Metals. Conservation of Marine Archaeological Objects. London: United Kingdom. Page 233.