Lost-wax casting sometimes called by the French name of cire perdue (from the Latin cera perduta) is the process by which a metal (such as silver, gold, brass or bronze) sculpture is cast from an artist's sculpture. Intricate works can be achieved by this method, primarily depending on the carver's skills. In industrial uses, the modern process is called investment casting. An ancient practice, the process today varies from foundry to foundry, but the steps which are usually used in casting small bronze sculptures in a modern bronze foundry are generally quite standardized.
Other names for the process include "lost mould," which recognizes that other materials besides wax can be used, including tallow, resin, tar, and textile;[1] and "waste wax process" or "waste mould casting", because the mould is destroyed to unveil the cast item.[2][3] Other methods of casting include open casting, bivalve mould, and piece mould.[3][4] Lost-wax casting was widespread in Europe until 18th century, when a piece-mold process came to predominate.
Contents |
Casts can be made of the wax model itself, the direct method; or of a wax copy of a model that need not be of wax, the indirect method. These are the steps for the indirect process:
Prior to silica-based casting molds, these molds were made of a variety of other fire-proof materials, the most common being plaster based, with added grout, and clay based. Prior to rubber molds gelatine was used.
The methods used for small parts and jewellery vary a bit from those used for sculpture. A wax is obtained, either from injection into a rubber mold, or it is custom-made in wax. Occasionally, a custom-made wax might be molded in rubber first as insurance against the loss of the unique wax and related labor costs incurred in carving it. The wax or waxes are sprued and fused onto a rubber base, called a "sprue base". Then a metal flask, which resembles a short length of steel pipe that ranges roughly from 1.5 to six inches tall and wide, is put over the sprue base and the waxes. Most sprue bases have a circular rim which grips the standard-sized flask, holding it in place. Investment (refractory plaster) is mixed and poured into the flask, filling it. It hardens, then is burned out as outlined above. Casting is usually done straight from the kiln either by centrifugal casting or vacuum casting.
The lost-wax process can be used with any material that can burn, melt, or evaporate to leave a mold cavity. Some automobile manufacturers use a lost-foam technique to make engine blocks. The model is made of polystyrene foam, which is placed into a casting flask, consisting of a cope and drag, which is then filled with casting sand. The foam supports the sand, allowing shapes that would be impossible if the process had to rely on the sand alone. The metal is poured in, vaporizing the foam with its heat.
In this process, the wax and the textile were both replaced by the metal during the casting process, whereby the fabric reinforcement would allow for a thinner model, and thus reduce the amount of metal expended in the mould.[5] Evidence of this process is seen by the textile relief on the reverse side of objects and is sometimes referred to as "lost-wax, lost textile". This textile relief is visible on gold ornaments from burial mounds in southern Siberia of the ancient horse riding tribes, such as the distinctive group of openwork gold plaques housed in the Hermitage Museum, Leningrad[5] The technique may have its origins in the Far East, as indicated by the few Han examples, and the bronze buckle and gold plaques found at the cemetery at Xigou.[6] Such a technique may also have been used to manufacture some Viking Age oval brooches, indicated by numerous examples with fabric imprints such as that of Castletown (Scotland).[7]
Some early literary works allude to lost-wax casting. Columella, a Latin writer of the first century AD, mentions the processing of wax from beehives in De Re Rustica, perhaps for casting, as does Pliny the Elder,[8] who details a sophisticated procedure for making Punic wax.[9] One Greek inscription refers to the payment of craftsmen for their work on the Erechtheum in Athens (408/7-407/6 BC). Clay-modellers may be using clay moulds to make terracotta negatives for casting or to produce wax positives.[9] Pliny portrays[8] Zenodorus as a well-reputed ancient artist of bronze statues,[10] and describes[8] Lysistratos of Sikyon, who takes plaster casts from living faces to create wax casts using the indirect process.[10]
Many bronze statues or parts of statues in antiquity were cast using the lost wax process. Theodorus of Samos is commonly associated with bronze casting.[8][11] Pliny also mentions the use of lead, which is known to help molten bronze flow into all areas and parts of complex moulds.[12] Quintilian documents the casting of statues in parts, whose moulds may have been produced by the lost wax process. Scenes on the early-5th century BC Berlin Foundry Cup depict the creation of bronze statuary working, probably by the indirect method of lost-wax casting.[13]
The lost-wax method is well documented in ancient Indian literary sources. The Silpasastras, a text from the Gupta Period, contains detailed information about casting images in metal. The fifth-century AD Vishnusamhita, an appendix to the Vishnu Purana, refers directly to the modeling of wax for making metal objects in chapter XIV: "if an image is to be made of metal, it must first be made of wax.”[14] Chapter 68 of the ancient Sanskrit text Mānasāra Silpa details casting idols in wax and is entitled "Maduchchhista vidhānam", or "lost wax method".[14][15] The Mānasollāsa (also known as the Abhilasitārtha chintāmani) was allegedly written by King Bhūlokamalla Somesvara of the Chalukya dynasty of Kalyāni in AD 1124-1125, and also provides detail about lost-wax and other casting processes.[14][15]
In a 16th-century treatise, the Uttarabhaga of the Śilparatna written by Srïkumāra, verses 32 to 52 of Chapter 2 ("Linga lakshanam") give detailed instructions on making a hollow casting.[14][15]
Early medieval writer Theophilus Presbyter, believed to be the Benedictine monk and metalworker Roger of Helmarshausen, wrote a treatise in the early to mid-12th century[16] that includes original work and copied information from other sources, such as the Mappae clavicula and Eraclius, De dolorous et artibus Romanorum.[16] It provides step-by-step procedures for making various articles, some by lost-wax casting: "The Copper Wind Chest and Its Conductor" (Chapter 84); "Tin Cruets" (Chapter 88), and "Casting Bells" (Chapter 85), which calls for using "tallow" instead of wax; "The Cast Censer". In Chapters 86 and 87 Theophilus details how to divide the wax into differing ratios, before moulding and casting, to achieve accurately tuned small musical bells. The 16th-century Florentine sculptor Benvenuto Cellini may have used Theophilus' writings when he cast his bronze Perseus.[15][17]
The lost-wax process was known to the Incas, the Aztecs and the Maya, as shown by archaeological evidence and a brief 1596 account of Aztec casting by the Spanish writer Releigh.[15]
Metalcasting began in India (now Pakistan) around 3500 BC in the Mohenjodaro area,[14] which produced earliest known lost-wax casting, the Indian bronze figurine named the “dancing girl” that dates back nearly 5,000 years to the Harappan period.[14][15] Other examples include the buffalo, bull and dog found from Mohenjodaro and Harappa,[1][15][18] two copper figures found at the Harappan site Lothal in the district of Ahmedabad of Gujurat,[14] and likely the covered cart with wheels missing and a complete cart with a driver found at Chanhudaro.[1][18]
During the post-Harappan period, hoards of copper and bronze implements made by the lost-wax process are known from Uttar Pradesh, Bihar, Madhya Pradesh, Orissa, Andhra Pradesh and West Bengal.[14] Gold and copper ornaments, apparently Hellenistic in style, made by cire perdue are found at the ruins at Sirkap. One example of this Indo-Greek art dates to the 1st century BC, the juvenile figure of Harpocrates excavated at Taxila.[14] Bronze icons were produced during the 3rd and 4th centuries AD, such as the Buddha image at Amaravati, the images of Rama and Kartikeya in the Guntur district of Andhra Pradesh.[14] A further two bronze images of Parsvanatha and a small hollow-cast bull were come from Sahribahlol, Gandhara, as well as the standing Tirthankara (2nd, 3rd century AD) from Chausa in Bihar.[14] Other notable bronze figures and images have been found in Rupar, Mathura (in Uttar Pradesh) and Brahmapura, Maharashtra.[14]
Gupta and post-Gupta period bronze figures have been recovered from the following sites: Saranath, Mirpur-Khas (in Pakistan), Sirpur (District of Raipur), Balaighat (near Mahasthan now in Bangladesh), Akota (near Vadodara, Gujurat), Vasantagadh, Chhatarhi, Barmer and Chambi (in Rajesthan).[14] Producing images by the lost-wax process reached its peak during from 750 AD to 1100 AD, and still remained prevalent in south India between 1500 AD and 1850.[14] The technique still remains well practiced throughout India, as well as neighbouring countries Nepal, Tibet, Ceylon, Burma and Siam.[15]
There is great variability in the use of the lost-wax method in South East Asia. The casting method of bronze during the Shang and Chou dynasties (approximately 1500 BC to 500 BC) has commonly been assumed to be by the lost-mould method.[15] Further investigations have revealed this not to be the case as it is clear that the piece-mould casting method was the principal technique used to manufacture bronze vessels in China.[19] The lost-wax technique did not appear in northern China until the 6th century BC.[20] Lost-wax casting is known as ro-gata in Japanese, and dates back to the Yayoi period of circa 200 BC.[15] The most famous piece made by cire perdue is the bronze image of Buddha in the temple of the Todaiji monastery at Nara.[15] It was made in sections between 743 AD and 749 AD, allegedly using seven tons of wax.[15]
Bangles (virtually non-existent in second millennium China) made by the lost-wax process are characteristic of northeast Thailand.[20] The inhabitants of Ban Na Di were casting bronze between 1200 BC and 200 AD, using the lost-wax technique to manufacture their bangles.[21] Some of the bangles from Ban Na Di revealed a dark grey substance between the central clay core and the metal, which on analysis was identified as an unrefined form of insect wax.[20][21] It is likely that decorative items, like bracelets and rings, were made by cire perdue at Non Nok Tha and Ban Chiang.[1]
There are technological and material parallels between northeast Thailand and Vietnam concerning the lost-wax technique.[1] The sites exhibiting artifacts made by the lost-mould process in Vietnam, such as the Dong Son drums come from the Dong Son,and Phung Nguyen cultures,[1] such as one sickle and the figure of a seated individual from Go Mun (near Phung Nguyen, the Bac Bo Region), dating to the Go Mun phase (end of the General B period, up until the 7th century BC).[21]
The lost-wax technique was used and developed for small-scale, and then large-scale, statues from circa 3500 BC to 2750 BC in Mesopotamia, made of copper and bronze.[22] A small lion pendant from Uruk IV was cast by cire perdue,one of the earliest surviving lost-wax castings, however, earlier lost-wax object examples come from the Nahal Mishmar hoard (Israel) made circa 3700 BC.[22][23] The Sumerian metalworkers were practicing lost-wax casting from approximately 3500 BC to 3200 BC.[24] Much later examples from northeastern Mesopotamia/Anatolia include the Great Tumulus at Gordion (end of 8th century BC), as well as other types of Urartian cauldron attachments.[25]
The Egyptians were practicing cire perdue from the mid 3rd millennium BC, shown by Early Dynastic bracelets and gold jewellery.[26][27] Inserted spouts for ewers (copper water vessels) from the Fourth Dynasty (Old Kingdom) were made by the lost-wax method.[27][28] Hollow castings, such as the Louvre statuette from the Fayum find appear during the Middle Kingdom, followed by solid cast statuettes (like the squatting, nursing mother, in Brooklyn) of the Second Intermediate/Early New Kingdom.[28] The hollow casting of statues is represented in the New Kingdom by the kneeling statue of Tuthmosis IV (British Museum, London) and the head fragment of Ramesses V (Fitzwilliam Museum, Cambridge).[29] Hollow castings become more detailed and continue into the Eighteenth Dynasty, shown by the black bronze kneeling figure of Tutankhamun (Museum of the University of Pennsylvania). Cire Perdue is used in mass-production during the Late Period to Graeco-Roman time when figures of deities are cast for personal devotion and votive temple offerings.[24] The nude-woman shaped handles of bronze mirrors are cast by the lost-wax process.[24]
The lost-wax technique was known in the Aegean during the Bronze Age, particularly in the second millennium BC.[30] Direct imitations and local derivations of Oriental, Syro-Palestinian and Cypriot figurines are found in Late Bronze Age Sardinia, with a local production of figurines from the eleventh to tenth century BC.[30]
Some Late Bronze Age sites in Cyprus have produced cast bronze figures of humans and animals: one example is the male figure found at Enkomi.[31] Three objects from Cyprus (held in the Metropolitan Museum of Art in New York) were cast as by the lost-wax technique, from the 13th and 12th centuries BC, namely, the Amphorae Rim, the rod tripod, and the cast tripod.[31]
The cremation graves (mainly 8th-7th centuries BC, but continuing until the beginning of the 4th century from the necropolis of Paularo (Italian Oriental Alps) contained fibulae, pendants and other copper-based objects that were made by the lost-wax process.[32] Etruscan examples, such as the bronze anthropomorphic handle from the Bocchi collection (National Archaeological Museum of Adria), dating back to the 6th to 5th centuries BC, were made by cire perdue.[33] Most of the handles in the Bocchi collection, as well as some Bronze vessels found in Adria (Rovigo, Italy) were made using the lost-wax technique.[33]
The better known lost-wax produced items from the classical world include the “Praying Boy” circa 300 BC (in the Berlin Museum), the statue of Hera from Vulci (Etruria), which, like most statues, were cast in several parts and then joined together.[34] Other, earlier examples that show this assembly of lost-wax cast pieces include the bronze head of the Chatsworth Apollo, and the bronze head of Aphrodite from Satala (modern Turkey, formerly Armenia) from the British Museum.[35] Geometric bronzes such as the four copper horses of San Marco (Venice, probably 2nd century) are other prime examples of statues cast in many parts.[27]
Cast bronzes were produced in Africa by the kingdoms of Benin, Yorubaland, Ife and in Igboland, including Igbo-Ukwu in Nigeria. Some portrait heads remain.[15]
The lost-wax casting tradition was developed by the peoples of Nicaragua, Costa Rica, Panama, Colombia, northwest Venezuela, Andean America, and the western portion of South America.[36] Lost-wax casting produced some of the region's typical gold wire and delicate wire ornament, such as fine ear ornaments. The process was employed in prehispanic times in Colombia's Muisca and Sinú cultural areas.[37] Two lost-wax moulds, one complete and one partially broken, were found in a shaft and chamber tomb in the vereda of Pueblo Tapado in the municipio of Montenegro (Department of Quindío), dated roughly to the pre-Columbian period.[38] The lost-wax method did not appear in Mexico until the 10th century,[39] and was thereafter used in western Mexico to make a wide range of bell forms.[40]
The intricate Gloucester candlestick (1104-1113 AD) was made as a single-piece wax model, then given a complex system of gates and vents before being invested in a mould.[3] The Dunaverney (1050 – 910 BC) and Little Thetford (1000 – 701 BC) flesh-hooks have been shown to be made using a lost-wax process. The Little Thetford flesh-hook, in particular, employed distinctly inventive construction methods.[41][42]
|
|||||||||||||||||||||||||||||||||||||||