Corinthian bronze

Highly valuable metal alloy in classical antiquity

Corinthian bronze, also named Corinthian brass or aes Corinthiacum, was a highly valuable metal alloy in classical antiquity. It is thought to be an alloy of copper with gold or silver (or both), although it has also been contended that it was simply a very high grade of bronze, or a kind of bronze that was manufactured in Corinth. It is referred to in various ancient texts, but no certain examples of Corinthian bronze exist today. However, it has been increasingly suggested that a number of artefacts previously described as niello in fact use a technique of patinated metal that may be the same as Corinthian bronze and is similar to the Japanese Shakudō. Its composition was long a mystery, but contemporary thinking is that Corinthian bronze was "a patinated alloy of copper with some gold and silver", perhaps the same as the hesmen kem or "black copper" of Ancient Egyptian art. This is shown by ancient texts to be a prestigious material, and apparently survives in a number of statuettes of "distinctive black patinated, inlaid metal", of which scientific analysis shows "that some have a highly unusual composition containing small amounts of gold, silver and arsenic in the alloy", and are broadly similar to Shakudō.

Of the known types of bronze or brass, not distinguished in classical antiquity and interchangeably known in Latin as aes and in Greek as χαλκός, Corinthian bronze was the most valuable. Statues, vases and vessels, or other objects formed of this metal were priceless, of greater value than if they had been made of silver or gold. Pliny the Elder distinguished it into three kinds, depending on the metal that is added to the copper base: in the first, gold is added (luteum); in the second, silver (candidum); in the third, gold, silver, and copper are equally blended. Plutarch and Cicero both comment that Corinthian bronze, unlike many other copper alloys, is resistant to tarnishing. Pliny also refers to a fourth, dark alloy, known as hepatizon. Petronius and other authors mocked the connoisseurs of their day who claimed to be able to identify it. however, remarked that this story is unbelievable, because most of the creators of the highly valued works in Corinthian bronze in Ancient Greece lived at a much earlier period than second century BC. although some sources describe the process by which it is created, involving heat treatment, quenching, leaching, and burnishing, in a process similar to depletion gilding. The lost ability to give an object made from bronze the appearance of gold or silver may be one strand behind the later alchemical quest to turn base metals into precious metals.

Articles made of Corinthian bronze are mentioned in the Bible. The Beautiful Gate (or Nicanor Gate) of the Second Temple in Jerusalem, mentioned in the Book of Acts 3:2–10, was a large, 18 metre (60 feet) wide structure said to be either solid, or covered in plates of, Corinthian brass. Another Biblical reference, in Book of Ezra 8:27, is usually translated "fine copper [or bronze], precious as gold". Similar alloys are found outside Europe. The Hông hee vases (1426) of China were said to be made of a similarly mixed metal allegedly formed when the Imperial palace was burnt to the ground. These vessels are of priceless value. An alloy of gold and copper, known as tumbaga was in widespread use in Pre columbian Mesoamerica, and has an essentially identical composition to Corinthian brass. A similar metallurgical process for "the colouration [chrôsis] of gold" is described in the 15th recipe in the Leyden papyrus X, from Thebes in Egypt, dated to the 4th century AD.