TERRACOTTA – 1

Post 565 by Gautam Shah

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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 crafts 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.

# ‘converted materials‘ = change their state, but cannot be reconverted back to their original state versus re-convertible materials, which can revert to their original state.

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Roof fragment of the Roman bath, at Bath, UK, Wikipedia image by Heinz-Josef Lucking

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.

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Earliest known ceramics are the Gravettian figurines dating bet 29000 to 25000 BC Image by “Petr Novak, Wikipedia”

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.

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Harappa miniature Votive images or Toy models Image by Trish Mayo from New York, US

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.

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Terracotta pottery fragment from Mathura sites, Now at Govt Museum Wikipedia image by Biswarup Ganguly

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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. Palladio extensively used terracotta friezes, column heads, architraves and other decorative elements replacing costly marble. The use of glazed or unglazed terracotta for free sculpture was revived.

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Vaishnavite temples of Bishnupur and other places in Eastern India were entirely built of Clay products like bricks and faced with terracotta figurines and panels.

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Modern Terracotta Pottery, India, Wikipedia image by McKay Savage from London UK

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MUD ARCHITECTURE

Post 426 – by Gautam Shah 

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Architecture and structures of mud or clay, for every conceivable purpose, exist in all parts of the world. In hilly regions of the world clay sediments have been used for packing the joint and as a masonry course leveller. Mud or clay is used because of the abundant supply, near zero cost of procurement, wet plasticity, mould-ability, insulating qualities, high thermal capacity, non toxicity, ecological friendly nature and simplicity of application. Mud as a forming material for architecture, structures or ceramics have some drawbacks like, shrinkages on drying, i.e., cracking, poor weathering qualities, lack of homogeneity in dry state, high water permeability -hygroscopic, poor bonding to a substrate -peel off, vulnerability to white ants and insects.

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Mud has seen renewed interest during the last Six to Seven decades. First interest in architecture was for its abundance and simplistic technology. Later, the material was favoured for its insulative qualities. During the last 4o years the mud buildings are being favoured for their Eco-friendliness, chiefly the recycle-ability aspect of it. The ideology of sustainability, with its varied interpretations, has supported experimentation for different uses.

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Some basic techniques of Mud construction are identified. These are: Sod, Rammed earth, Cob (cobb or clom), Adobe, Wattle and daub Compressed earth block methods. These techniques differ in details, from region to region, type of soils, natural moisture content and availability of additional water, additives, reinforcements and support form-work within reach. The mix design and forming techniques also depend on building elements (wall, slab, etc.), architectural elements and surface finish or applique decorations.

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Mud architecture presents fascinating forms. The quality of space formation, the suitability for range of basic architectonic elements, adaptability to different usages, and the universal availability, make mud a very coveted material. The love affair is very poignant during the academic period of designers. The passion, however, gets muted over the years, for variety of reasons, such as lack of the clientele, the place, scope and sponsorship for experimentation and the irrelevance of the technology at locations where the educated designer will operate. There are many other reasons for a failed take off for ‘low technology and eco-friendly’ endeavours. Mud, is reckoned to be a sustainable material, of very relevant (‘green’) technology, non toxic, universally available and completely recyclable material.

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These concepts remain valid so far as one can use the mud architecture concurrently with matching ‘lifestyle’ if one is conducting. A personal habitat of mud and to maintain (sustain) it for a long period, are two different things. A mud building is a very fragile entity and needs day to day care. Such concerns cannot be assigned to any outsider or agency. The cost of daily upkeep can turn out to be very high. And even if one can afford the cost, (which could be equal to the cost of a new structure), takes lots of time, practically a full time vocation.

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Mud built-form cannot be conceived as a drawn plan or scheme. A person who constructs it must improvise it on own. The execution of such form cannot happen quickly, and during the period whatever that has been constructed will need updating and improvisation. Some of the key elements of built form, material behaviour, form and space organization exist in the society that has been using mud for generations. These innate capacities can be reinforced by being not only an active participant on the site, but by being an inhabitant of the entity. Only an inhabitant of the mud architecture can sustain it.

4 Mud_plaster_over_straw_bales_wallDesigners cannot, and must not meddle in mud architecture design or execution. A design student may be asked to design one and perhaps execute it, as a learning exercise. The fashionable word coined by teachers who never practice, or have never done, is “hand on experience” in material-form-and the technological implications.

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