Post 565 –by Gautam Shah
Terracotta is one of the oldest converted materials used by humans. By firing a shaped clay object, it not only gets a permanent form but attains superior strength and properties. Terracotta or baked clay ceramics have been used for cooking pots, storage utilities, artefacts, monetary units, toys, adornments, statuettes, sarcophagi, masonry units like bricks, roofing tiles, and other architectural elements. The art and craft of terracotta have been practised in almost all regions of the world. Terracotta items of small sized beads to human size statues and jars have been produced. The qualities of local clays have contributed to the colour and density (porosity), whereas the firing techniques and fuel have exploited the baking temperature to impart unique properties.
In archaeology a terracotta is a baked clay product formed by processes other than on a potter’s wheel. Baked clay items used in buildings are called Earthenware goods, whereas pottery items formed on potters’ wheel are popularly known as earthenware pottery or ceramics. Terracotta items are unglazed and created through single firing process. Faience is made from a vitreous frit (baked powdered of ceramic clays), and also called white-earthenware or lighter terracotta when created with the self-glazing process. Fine ceramic beads, figures and other small objects were made in Egypt (000 BC), Mid-East, Indus Valley and elsewhere.
Clays show Three transformation stages. First: Clay can take large amounts of water achieving a fluid or watery mass to pasty form. It becomes so plastic that can be moulded to any shape. Two: The formed clay, when dries out, still retains the shape, and its surface can be fashioned to different finishes. Three: The dried form on firing becomes permanent, and the mass achieves greater density. These processes use less energy and labour than the metal forming. The clay processes are, both corrective and additive, unlike wood working, which is basically a deductive process, unless one uses joinery techniques. Clay (earthenware) processes, at a later stage suffused the stoneware, porcelain and glass making, due to involvement of ‘earthy’ minerals and the heat treatments. In architecture clay products competed against stones, and for household items formed with metals. Stones are not available in all locations and metals need higher technology, compared with a universal material, the clay.
Plasticity of clay is one its plus quality that is available in no other materials except the flour dough. Clay items can be made by strip or coil stacking, moulding, wet engraving, or shaping on a wheel. Clay can be liquidized and poured into moulds with very fine details such as hair, costume, drapery or facial features. Such details are difficult with bronze casting. Compared to stonework, the finished products of clay are far lighter in weight, and easier to paint. Terracotta products shrink on drying, which is both an asset and drawback. Shrinkage on drying allows easy removal from casting moulds, but the same in heavy mass items, causes cracking. Clay is considered the most sustainable and eco-friendly product.
Baked clay products or Terracotta have a tough surface that can last for years in buried or open conditions. It is, however, vulnerable to moisture and salts. Fired terracotta is water absorbent, but surface-burnishing before firing compacts the surface reducing the porosity. Raw clay tablets were inscribed with a cuneiform script, and fired for indelible record keeping. The use of terracotta or earthenware nearly died with the Roman empire. Throughout the world, though terracotta continued to be used for building-brick, roof and wall cladding tiles. This began to change in Europe and at other places past 14th C, with high temperature firing to produce the stoneware. Italy and Germany began to produce moulded and carved terracotta for architectural friezes, column capitals and medallions. The use of glazed or unglazed terracotta for free sculpture was revived.
(Future articles will cover: Architectural elements of Terracotta, Craft of Terracotta and Architecture of bricks).