Egyptian faience

Type of Ancient Egyptian sintered quartz ceramic

Egyptian faience is a sintered quartz ceramic material from Ancient Egypt. The sintering process "covered [the material] with a true vitreous coating" as the quartz underwent vitrification, creating a bright lustre of various colours "usually in a transparent blue or green isotropic glass". Its name in the Ancient Egyptian language was , and modern archeological terms for it include sintered quartz, glazed frit, and glazed composition. is distinct from the crystalline pigment Egyptian blue, for which it has sometimes incorrectly been used as a synonym. The well known blue hippopotamus figurines, placed in the tombs of officials, can be up to long, approaching the maximum practical size for Egyptian faience, though the Victoria and Albert Museum in London has a sceptre, dated 1427–1400 BC.

It is called "Egyptian faience" to distinguish it from faience, the tin glazed pottery whose name came from Faenza in northern Italy, a center of maiolica (one type of faience) production in the late Middle Ages. Egyptian faience was both exported widely in the ancient world and made locally in many places, and is found in Mesopotamia, around the Mediterranean and in northern Europe as far away as Scotland. The term is used for the material wherever it was made and modern scientific analyses are often the only way of establishing the provenance of simple objects such as the very common beads. The term is therefore unsatisfactory in several respects, although clear in an Ancient Egyptian context, and is increasingly rejected in museum and archaeological usage. The British Museum now calls this material "glazed composition", with the following note in their online collection database: <blockquote>The term is used for objects with a body made of finely powdered quartz grains fused together with small amounts of alkali and/or lime through partial heating. The bodies are usually colourless but natural impurities give them a brown or greyish tint. Colourants can also be added to give it an artificial colour. It can be modelled by hand, thrown or moulded, and hardens with firing. This material is used in the context of Islamic ceramics where it is described as stonepaste (or fritware). Glazed composition is related to glass, but glass is formed by completely fusing the ingredients in a liquid melted at high temperature. This material is also popularly called faience in the contexts of Ancient Egypt and Ancient Near East. However, this is a misnomer as these objects have no relationship to the glazed pottery vessels made in Faenza, from which the faience term derives. Other authors use the terms sintered quartz, glazed frit, frit, composition, Egyptian Blue, paste or (in the 19th century) even porcelain, although the last two terms are very inappropriate as they also describe imitation gems and a type of ceramic. Frit is technically a flux. As early as the Predynastic graves at Naqada, Badar, el Amrah, Matmar, Harageh, Avadiyedh and El Gerzeh, glazed steatite and faience beads are found associated with these semi precious stones. The association of faience with turquoise and lapis lazuli becomes even more conspicuous in Quennou's funerary papyrus, giving his title as the director of overseer of faience making, using the word which strictly means lapis lazuli, which by the New Kingdom had also come to refer to the 'substitute', faience.

The discovery of faience glazing has tentatively been associated with the copper industry: bronze scale and corrosion products of leaded copper objects are found in the manufacture of faience pigments. However, although the likelihood of glazed quartz pebbles developing accidentally in traces in copper smelting furnaces from the copper and wood ash is high, the regions in which these processes originate do not coincide.

Although it appears that no glass was intentionally produced in Egypt before the Eighteenth Dynasty (as the establishment of glass manufacture is generally attributed to the reign of Thutmose III), it is likely that faience, frit and glass were all made in close proximity or in the same workshop complex, since developments in one industry are reflected in others. Egyptian faience is a non clay based ceramic composed of crushed quartz or sand, with small amounts of calcite lime and a mixture of alkalis, displaying surface vitrification due to the soda lime silica glaze often containing copper pigments to create a bright blue green luster. This property, together with the angularity of silica particles, accounts for the gritty slumps formed when the material is wetted, rendering faience a difficult material to hold a shape. If pressed too vigorously, this material will resist flow until it yields and cracks, due to its limited plastic deformation and low yield strength. The use of alkalis as binders, in the form of natron or plant ash, produced suitable results in experiments.

Three methods have been hypothesized to shape the body of faience objects: modeling, moulding and abrasion, the last being used in conjunction with the first two. The faience paste could then be pressed into the mold, and following drying, be re worked through surface abrasion before firing. Wheel throwing, possibly occurring from the New Kingdom onwards, is certainly established by the Greco Roman period, when large amounts of clay seem to have been added to the faience body. Ptolemaic and Roman faience tends to be typologically and technologically distinct from the earlier material: it is characterized by the widespread use of moulding and high relief on vessels. A very unusual and finely made group of figures of deities and falcons in the Metropolitan Museum of Art in New York, apparently representing hieroglyphs that are elements from a royal inscription, perhaps from a wooden shrine, is decorated in a form of champlevé (typically a technique for enamel on metal). Depressions in the faience body were filled with coloured "vitreous pastes" and refired, followed by polishing. Polychrome pieces were usually made by inlaying different colours of paste.

The technology of glazing a siliceous body with a soda lime silica glaze employs various methods discovered over time: namely application, efflorescence and cementation glazing.

In the application method, formerly assumed to be the only one used for faience glazing; silica, lime and alkalis are ground in the raw state to a small particle size, thus mixed in water to form a slurry which is then applied to the quartz core. As the water in the body evaporates, the salts migrate to the surface of the object to recrystallize, creating a thin surface, which glazes upon firing.]] >

Cementation glazing, a technique discovered in the Middle Kingdom, is also a self glazing technique. In this method the artifact, while buried in a glazing powder with a high flux content, is heated inside a vessel, causing the fusion of the object with the cement. During firing, the flux migrates to the quartz and combines with it to form a glassy coating.]] >

A vapour glaze reaction similar to salt glazing, as an alternative glazing process, has been suggested. In this process, the vaporization or dissociation of salts leads to vapour transport through the enveloping powder to the quartz body where a glaze is formed.

Although glaze compositions vary regionally and chronologically, depending on the formation of the body and the glazing process employed, objects produced with different glazing techniques do not exhibit immediate diagnostic chemical variations in their compositions. The recognition of the various glazing techniques, through microscopic observations of the degree of sintering and the vitreous phase of quartz body, is also ambiguous. For instance, objects with applied glazes and those which may have been glazed by efflorescence have overlapping characteristic features. The following proposed criteria are subject to variation caused by increases in flux concentration, firing temperatures and time at peak temperatures. Body color, density and luster provided the basis of the first typology developed for faience: seven variants were proposed by Lucas and Harris and still permit the archaeologist to distinguish faience objects during field sorting.]] >

The excavations led by Petrie at Tell Amarna and Naucratis have reported finding workshop evidence. Lucas documented a large number of molds at the palace area of Amenhotep III at Qantir, from 19th to 20th Dynasties, and at the palace area of Naucratis, also described in different sources as a scarab maker's and faience factory.]] >

Although recent excavations at the archaeological sites of Abydos and Amarna have supplemented our knowledge of the ancient production of faience gained from the earlier excavated sites of Lisht, Memphis and Naukratis, the differentiation of glass furnaces from faience kilns still remains problematic.

A number of ceramists are experimenting with Egyptian faience, though some of the compositions bear only a passing resemblance to the original Egyptian formulae. There has also been a recent interest in the use of Egyptian faience in 3 d printing technology. It may be possible to fire faience like materials in a microwave.