The term faience comes from a kind of brightly-colored glazed earthenware developed during the Renaissance in France and Italy. The word is derived from Faenza, a town in Italy, where factories making the tin-glazed earthenware called majolica (also spelled maiolica) were prevalent. Majolica itself derived from North African Islamic tradition ceramics and is thought to have developed, oddly enough, from the region of Mesopotamia in the 9th century AD.
Faience-glazed tiles decorate many buildings of the middle ages, including those of the Islamic civilization, such as the Bibi Jawindi tomb in Pakistan, built in the 15th century AD, or the Timuid dynasty (1370-1526) Shah-i-Zinda necropolis in Uzbekistan, which you can see if you click on the hippo illustration.
Ancient or Egyptian faience, on the other hand, is a completely manufactured material created perhaps to imitate the bright colors and gloss of hard-to-get gems and precious stones. Called the "first high-tech ceramic", faience is a siliceous vitrified and glost ceramic, made of a body of fine ground quartz or sand, coated with an alkaline-lime-silica glaze. It was used in jewelry throughout Egypt and the Near East beginning about 3500 BC. Forms of faience are found throughout the Bronze Age Mediterranean, and faience objects have been recovered from archaeological sites of the Indus, Mesopotamian, Minoan, and Egyptian civilizations.
Scholars suggest but are not completely united that faience was invented in Mesopotamia in the late 5th millennium BC and then imported to Egypt. Evidence for the 4th millennium BC production of faience has been found at the Mesopotamian sites of Hamoukar and Tell Brak. Faience objects have also been discovered at predynastic Badarian (5000-3900 BC) sites in Egypt. Matin (2014) has argued that mixing cattle dung (commonly used for fuel), copper scale resulting from copper smelting, and calcium carbonate creates a shiny blue glaze coating on objects and may have resulted in the invention of faience and associated glazes during the Chalcolithic period.
Faience was an important trade item during the Bronze Age; the Uluburun shipwreck of 1300 BC had over 75,000 faience beads in its cargo. Faience continued as a production method throughout the Roman period into the first century BC.
Ancient Faience Manufacturing Practices
Types of objects formed out of ancient faience include amulets, beads, rings, scarabs, and even some bowls. Faience is considered one of the earliest forms of glass making.
Recent investigations of Egyptian faience technology indicate that recipes changed over time and from place to place. Some of the changes involved using soda-rich plant ashes as flux additives--flux helps the materials fuse together at high-temperature heating. Basically, component materials in glass melt at different temperatures, and to get faience to hang together you need to moderate the melting points. However, Rehren has argued that the differences in glasses (including but not limited to faience) may have to do more with the specific mechanical processes used to create them, rather than varying specific admixture of plant products.
The original colors of faience were created by adding copper (to get a turquoise color) or manganese (to get black). Around the beginning of glass production, about 1500 BC, additional colors were created including cobalt blue, manganese purple, and lead antimonate yellow.
Three different techniques for producing faience's glazes have been identified to date: application, efflorescence, and cementation. In the application method, the potter applies a thick slurry of water and glazing ingredients (glass, quartz, colorant, flux and lime) to an object, such as a tile or pot. The slurry can be poured or painted on the object, and it is recognized by the presence of brush marks, drips, and irregularities in thickness.
The efflorescence method involves grinding quartz or sand crystals and mixing them with various levels of sodium, potassium, calcium, magnesium, and/or copper oxide. This mixture is formed into shapes such as beads or amulets, and then the shapes are exposed to heat. During heating, the formed shapes create their own glazes, essentially a thin hard layer of various bright colors, depending on the particular recipe. These objects are identified by stand marks where the pieces were placed during the drying process and variations in glaze thickness.
The cementation method or Qom technique (named after the city in Iran where the method is still used), involves forming the object and burying it in a glazing mixture consisting of alkalis, copper compounds, calcium oxide or hydroxide, quartz, and charcoal. The object and glazing mixture are fired at ~1000 degrees Centigrade, and a glaze layer forms on the surface. After firing, the left-over mixture is crumbled away. This method leaves a uniform glass thickness, but it is only appropriate for small objects such as beads.
Replication experiments reported in 2012 (Matin and Matin) reproduced the cementation method, and identified calcium hydroxide, potassium nitrate, and alkali chlorides are essential pieces of the Qom method.
Charrié-Duhaut A, Connan J, Rouquette N, Adam P, Barbotin C, de Rozières M-F, Tchapla A, and Albrecht P. 2007. The canopic jars of Rameses II: real use revealed by molecular study of organic residues. Journal of Archaeological Science 34:957-967.
De Ferri L, Bersani D, Lorenzi A, Lottici PP, Vezzalini G, and Simon G. 2012. Structural and vibrational characterization of medieval like glass samples. Journal of Non-Crystalline Solids 358(4):814-819.
Matin M. 2014. An Experimental Investigation into the Accidental Invention of Ceramic Glazes. Archaeometry 56(4):591-600. doi:10.1111/arcm.12039
Matin M, and Matin M. 2012. Egyptian faience glazing by the cementation method part 1: an investigation of the glazing powder composition and glazing mechanism. Journal of Archaeological Science 39(3):763-776.
Olin JS, Blackman MJ, Mitchem JE, and Waselkov GA. 2002. Compositional Analysis of Glazed Earthenwares from Eighteenth-Century Sites on the Northern Gulf Coast. Historical Archaeology 36(1):79-96.
Rehren T. 2008. A review of factors affecting the composition of early Egyptian glasses and faience: alkali and alkali earth oxides. Journal of Archaeological Science 35(5):1345-1354.
Shortland A, Schachner L, Freestone I, and Tite M. 2006. Natron as a flux in the early vitreous materials industry: sources, beginnings and reasons for decline. Journal of Archaeological Science 33(4):521-530.
Tite MS, Manti P, and Shortland AJ. 2007. A technological study of ancient faience from Egypt. Journal of Archaeological Science 34:1568-1583.
Tite MS, Shortland A, Maniatis Y, Kavoussanaki D, and Harris SA. 2006. The composition of the soda-rich and mixed alkali plant ashes used in the production of glass. Journal of Archaeological Science 33:1284-1292.
Walthall JA. 1991. Faience in French colonial Illinois. Historical Archaeology 25(1):80-105.
Waselkov GA, and Walthall JA. 2002. Faience Styles in French Colonial North America: A Revised Classification. Historical Archaeology 36(1):62-78.