I believe that my work would surely be almost a seed without fruit and that I would fail in that cause which disposed me to satisfy your request to write and form this work if, while labouring on it, 1 did not tell you of the art of casting, since it is a necessary means to very many ends. It is especially necessary since this art and work is not well known, so that no one can practice it who is not, so to speak, born to it, or who does not have much talent and good judgment. For this reason and also because it is closely related to sculpture, whose arms are the support of its life, it is very highly esteemed… it is a profitable and skilful art and in large part delightful.
(Biringuccio, in Pirotechnia, 1540)
The history of metal casting is the history of metallurgy. Metals produced in a furnace are melted and cast to form useful objects, whether a piece of jewelry, an agricultural tool, or a weapon. Objects made of gold, silver, copper, bronze, brass, tin, lead, and iron conserved in museums are a testimony to the cleverness of the ancient metal workers. The history of casting is also the history of art since most castings are made by artists. Ancient Egyptian wall paintings give an excellent illustration of the melting and casting of gold and copper. Most of the important Egyptian castings were used for making jewelry and masks. Copper was traded in the form of large cast ingots.
The Colossus of Rhodes is an immense bronze statue of Apollo the Sun God and protecting deity of Rhodes, constructed during the period from 292 to 280 BC, which stood at the entrance to Rhodes Harbour. It fell to pieces in 224 BC when an earthquake struck the island. It remained there for centuries until the Arabs gained possession of the island in 672 AD and sold what remained as scrap metal. The description of the statue is known only through writings of the Roman historian Pliny who visited the island in the first century AD. The statue stood about 32 metres high and weighed 300 tonnes. The Etruscans and Romans also cast large bronze statutes.
In ancient China, massive bronze vessels were cast during the Han Dynasty (206 BC to 220 AD). The brilliant age of Japanese bronze founding dates back to the introduction of Buddhism, in the sixth century AD in Nara, the ancient capital of Japan. Among the Japanese creations of this period was the colossal 380-tonne seated Buddha of Todaiji, gilded with 440 kilograms of gold. In India, Parvati, the consort of Shiva, is the nourishing and life-giving bronze statue dating back to about 950 AD.
The same technique used for casting large bells in ancient China was later used in Europe to cast cannons when gun powder became known around 1250 AD. The fall of Constantinople in 1453 was a turning point in the history of the world; city walls were bombarded by stone balls thrown by huge cannons constructed by the Turks. During medieval times in Europe, the foundry men and smiths produced weapons and armour, household utensils and tools, swords, and other implements demanded by the feudal lords. However, it was the church that provided the greatest outlet for their skills in bell founding to supply bells for the cathedrals and abbeys. Because of its size and importance, bell founding raised the casting of metal to the class of a practical art. At the time of war, bells were often melted down and made into weapons.
Some medieval technical manuals, such as De Diversibus Artibus (On the Different Arts), the earliest known foundry text, written around 1120 by the German Benedictine monk Theophilus Presbyter (circa 1070-1125), give detailed accounts of the tools and equipment used for the goldsmiths’ work. The invention of movable and cast lead type for the printing press in 1450 was an important application of casting.
The casting of bells and cannons was described at length by Vannoccio Biringuccio (1480-1539), the head of the Papal Foundry in Rome, in his Pirotechnia, published in 1540, one year after his death. While at the Paris Arsenal, Pierre Surirey de Saint Remy (1645-1716) wrote a two-volume book in 1697 entitled Memoires d’artillerie, which contained valuable information on casting cannons. The close ties between casting and pottery indicate that the two arts must have developed simultaneously. It was the potter’s art - the selection and compounding of suitable clays, their moulding, and proper firing - that gave the foundry the crucible for handling molten metals. Bells were generally decorated to give them an additional message or to keep danger away, while cannons were usually decorated with the coat of arms of the owner.
The Lost Wax Process
The lost wax process dates back thousands of years. The artists and sculptors of ancient Egypt and Mesopotamia, the Han Dynasty in China, the Aztec goldsmiths of pre-Columbian Mexico, and the Benin civilization in Africa used this method of casting to produce their artwork in copper, bronze, and gold.
In this method, the smith creates a pattern for the casting by covering one of the cores with beeswax and carefully modelling it into the desired shape. When the wax form is finished to the artist’s satisfaction, it is covered in a thick coating of clay. The cores are made to be self supporting. This mould is allowed to air dry. When a batch of moulds has been created and is ready for casting, it is placed in a fire and heated so that the wax melts. The wax is collected through a runner and can be reused after any foreign matter is removed. The clay moulds are further heated to a point where they are sufficiently hard. This permits the pouring of the molten metal without causing the shell to burst. The moulds are then placed upright on the floor and molten brass is poured into the open mould. Soon after casting, the molds are broken open, the shell knocked off, and the final object is cleaned, filed, and polished. Coating the wax pattern with layers of clay became known as investment.
Shortly after the Dark Ages in Europe, the industrious sculptor and goldsmith Benvenuto Cellini (1500–1571) began to make use of the lost wax method of casting, which he learned from the writings of the monk Theophilus. In his autobiography, Cellini described in detail the casting of his Perseus and the Head of Medusa. This three and a half ton statue was completed in 1554 and was unveiled at the Loggia dei Lanzi in Florence, Italy, where it stands to this day. The process was developed to a high degree of excellence, as is attested to by the many finely detailed statues, jewelry, and artefacts from antiquity. This technique was rediscovered in 1897 by the dental profession for producing crowns and inlays.