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Patina is a coating of various chemical compounds such as oxides or carbonates formed on the surface of metal during exposure to weathering. The green patina that forms naturally on copper and bronze is known as verdigris and consists of copper carbonate. Patina also refers to accumulated changes in surface texture and colour that result from normal use of an object such as a coin or a piece of furniture. Artists and metalworkers often deliberately add patinas as a part of the original design and decoration of art and furniture, or to simulate antiquity in newly-made objects. The chemical process by which a patina forms is called patination, and a work of art coated by a patina is said to be patinated. wide range of chemicals, both household and commercial, can give a variety of patinas. They are often used by artists as surface embellishments either for color, texture, or both. Patination composition varies with the reacted elements and these will determine the color of the patina. Exposure to chlorides leads to green, while sulfur compounds (such as "liver of sulfur") tend to brown. For artworks patination is deliberately accelerated by heat. Colors range from matte sandstone yellow to deep blues, reds and various blacks, sometimes with the surface sheen enhanced by waxing for artwork displayed indoors. |
