The fine varnish- like green rust found covering coins that have been long embedded in particular soils.Hence patinated, patinous, aa., patination n. green, on surface of old bronze, esteemed as ornament. A dish or plate of metal or earthenware a patella.

The color or incrustation which age gives to works of art especially, the green rust which covers ancient bronzes, coins, and medals.

Copper corrosion may appear as powdery, pinhead-size blue-green deposits, or it can be more scattered.If you're looking for meanings of the word patina, As I noted above, chloride salts and copper do not make a good combination, and the “bronze disease” cycle may be activated if unstable bronzes are stored or displayed at humidities above 40 percent. Conservators frequently term it “bronze disease.” Preventing “Bronze Disease”Ĭonservators work to identify particularly problematic bronze objects and prevent further deterioration. Unchecked, this process can result in significant damage, acting as an insidious disease. The mineral formation process re-releases the chloride, which once again reacts with copper to form yet more copper chloride, and the cycle continues. The most common of these minerals are atacamite and paratacamite (both named in the early 20th century after the Atacama Desert of Chile). Salt forms a mild hydrochloric acid that attacks the copper in the alloy, resulting in the formation of a copper chloride and minerals. Salt is bad for all metals, but in copper alloys it works in a particularly damaging recurring cycle. Bronzes buried in salty environments can absorb salt over the years, and after excavation, the salt remains within the slightly porous bronze structure.

Of particular concern are chlorides (table salt!) present in certain terrestrial environments, and of course in the sea. In some instances, however, they may be unstable (“vile”) and present continued preservation issues in both storage and display. In fact, we seldom clean to the point that we reveal metal.Ĭopper burial patinas are generally chemically stable and confer some protection to the object. In the past, restorers would often remove surface oxidation layers in a mistaken belief that the surface had to have a metallic appearance to truly be representative of “bronze.” However, today we know removing these layers can also eliminate much of the surface detail, and we conservators employ much less aggressive cleaning methods. In addition to being colorful, patinas sometimes preserve details of the original surface layer of the bronze sculpture-such as the original surface contours and evidence of surface tooling such as polishing, chiseling, and scraping. Although some metallic bronze core may remain, the surface gradually reverts to its original state as an ore, reducing the metal content. The colors we see on ancient bronzes today are mostly a result of copper oxidizing to form red-brown cuprite, green malachite, and bluish azurite. Virus aerugo (vile or virulent patina) was destructive and disfiguring. Aerugo nobilis (stable bronze, or rust), today termed “noble patina,” was stable and enhanced surface appearance. Roman historian and writer Pliny distinguished between two types of patinas. As examples, the bronze shown above from the site of Vani in the Republic of Georgia buried in a sandy soil has an even, pale-blue patina, while the Victorious Youth shown below, a sea burial, has a variegated patina with a range of colors.īronze surface coloration and alteration was understood even in ancient times. Today, ancient bronzes have burial patinas with a range of colors including red-browns, browns, greens, blues, and even black. These colors and so-called “burial patinas” have value in themselves, testifying to an object’s antiquity. Ancient bronzes, therefore, have a range of colors that have less to do with their original use and more to do with how they survived through time. To add to their stories, many bronzes discovered hundreds of years ago were restored according to the tastes of the day. Following their useful life (over 2,000 years ago!), they were abandoned and buried in a variety of environments including rivers, oceans, and underground. It’s difficult to imagine that these objects were once part of a colorful world where marble was painted and bronze patinated (surface-treated) to produce more naturalistic colorations.īronze sculptures were cast from different alloys of copper, tin, and lead.

Ancient patina definition