Surface appearance of materials, in particular metals, that results naturally from many years of use or corrosion. Patina may also be imparted artificially by the application of various substances or by chemical treatment. The chemical mechanisms by which materials develop a patina and the appropriate conservation treatments are covered in the articles on specific materials (e.g. Silver, Copper); similarly, some of the more specialized patination techniques applied to metals are described in Metal, §VI. Hence, only the aesthetic and historical aspects of the subject will be discussed here.
Some metals, notably copper alloys that have been buried for long periods, acquire a distinctive patina that is often admired in its own right. Also most materials, including wood, ivory and many stones, gradually develop a patina brought about by years of use, cleaning and polishing, together with the slow action of the air. Thus patina is partly a manifestation of the age of the piece, and as such it is valued for the aura of history that it endows. Although patina is a prized symbol of authenticity, it is not the original surface, nor does it represent the original appearance; therein lies a contradiction that has long vexed curators, collectors and restorers. How can something that is clearly so intrinsic to the object not be ‘genuine’?
Wooden furniture may have been varnished or painted originally, but repeated wax polishing over the years, coupled with fine and sometimes not so fine scratches, will have worn through the original varnish causing some polish and dirt to become ingrained in the wood. This will give the smooth, rounded, rather dark and variegated surface characteristic of antique furniture. The patination on stone will primarily be the result of weathering, which can, for example, give a warm, honey-coloured patina to marble that originally may have been white. In the case of ancient Classical sculpture, the problem of its original appearance, and to what extent it would have been painted, has been much debated. This is even more true of bronze sculpture. Collectors came to associate ancient bronzes with the fine green patinas that developed over the centuries and therefore assumed that this was how they originally appeared. Ancient bronzes were collected in China from c. AD 1000, and in the Song (960–1279), Ming (1368–1644) and Qing (1644–1911) periods bronzes dug from the ground were copied and given an artificial patina of ground-up malachite to satisfy the whims of collectors.
The bronzes of Classical antiquity, on the other hand, were probably left unpatinated (Hill). The few surviving contemporary wall paintings that depict bronze statues in landscapes or streetscenes show them as bronze-coloured, never green or black. Also, many of the surviving bronzes have details (e.g. lips or nipples) made of copper to show red against the gold of the bronze. This could only have been apparent if the metal was kept untarnished. There are some Classical references to treating bronzes with oil, and practical experiment as well as contemporary comments suggest this would probably impart a dark hue to the otherwise unpatinated metal. However, collectors from the Renaissance onwards believed that the ancient bronzes originally had a black patina, and sometimes the natural green patina on a genuine antiquity was repatinated to give the black patina the collector felt it should have had. Thus, for example, the bronzes (London, BM) that belonged to the 18th-century collector Richard Payne Knight were repatinated to fit his perception of the past.
In the Renaissance, bronze sculptures were normally given a simple patina with coloured varnishes or oils, followed by careful polishing to create the desired finish. Chemical patination was rarely used, except to imitate genuine patinas on forgeries, until the 19th century. This was probably the great age of surface treatments with splendid polychrome effects produced by a variety of methods including oils and varnishes, electrochemical processes, smoking and a plethora of chemical treatments. The recipes used by craftsmen were often closely guarded secrets, but some were published by such teachers as Arthur Hiorns. At the end of the 19th century the arrival in Europe of Japanese metalwork with sophisticated patination prompted further innovation, and some exciting and elaborate treatments were applied to Art Nouveau metalwork around the turn of the century. In the 20th century the regular application of complex surface treatments ceased, along with many other craft techniques, although from the 1970s attempts were made, mainly in art schools and by artist-craftsmen, to continue some of the surface treatments.
P. T. Craddock
From Grove Art Online
© 2009 Oxford University Press