Clay products are essentially products that are fundamentally derived from clay/earth. The major components of clay products are bricks and tiles followed by refractories, Terra cotta, porcelain, etc. Brick and other ceramic products have an almost mesmerizing allure due to the rhythmic patterns created when they are installed.
Bricks
They are both warm and sophisticated. Bricks have been used for construction since before Egyptian times and continue to be used today. Brick is not as massive and robust as stone, but it possesses some of stone’s best attributes. Brick is dense and holds and releases heat very slowly. As humans discovered that cities built of wood burn readily, they turned to brick as a material with which to clad buildings and help make them less prone to the ravages of fire. Relatively inexpensive and easy to install, brick became the defining element of domestic construction in many Northern European and North American cities in the early 18th century. Vast sections of London and New York city are etched in our minds with the color and pattern of brick facades.
Bricks are obtained by moulding clay in rectangular blocks of uniform dimensions and then drying and burning these blocks. As bricks are of uniform size, they can be effectively arranged, also they do not require any dressing. This makes the art of bricklaying very simple and therefore does not require skilled workers.
Composition of Brick Earth
- Alumina
- Silica
- Lime
- Iron oxides
- Magnesia
Qualities of good bricks
- Well burnt, table mounted, sharp and square edges
- Free from cracks, uniform in shape and colour
- They should be devoid of voids
- Must not excessively absorb water
- Should be sufficiently hard and durable
- Should have low thermal conductivity to resist fires
Tiles
Tiles may be defined as thin slabs of brick which are burnt in kiln. They are thinner than bricks and hence they should be carefully handled to avoid any damage or cracks. Tiles can be classified into two groups
- Common tiles – Mainly used for paving, flooring and roofing
- Encaustic tiles – Used for decorative purposes in floors, walls, ceilings and roofs.
Types of tiles
- Drain tiles
- Flooring or paving tiles
- Roof tiles
- Allahabad tiles
- Corrugated tiles
- Flat tiles
- Flemish tiles
- Guna tiles
- Mangalore tiles
- Pan tiles
- Pot tiles
Terra Cotta
Terra cotta is a type of earthenware or porous pottery that is made of clays and glazed with glazes containing galena. Literally Terra means earth and cotta means baked, thus terra cotta means baked earth. Like brick, terra-cotta tiles started as handmade elements made from local clay and earth in many parts of the world. These tiles can be glazed or unglazed and come in a wide variety of colors and shading due to differences in earth and clay. Most, however, have distinct shading in the red or ocher range. The irregularities inherent in terra-cotta tiles produced by the handmade process give them great character and vitality. Machine-made tiles are more uniform yet retain the colorful and rustic feel of handmade tiles.
Terra cotta is mainly used in decorative, designing and ornamental purposes.
Varieties of terra cotta
- Porous terra cotta – It is fireproof and soundproof, it can be chiselled, sawn and nailed easily with nails and screws. It is light in weight but structurally very weak.
- Polished terra cotta – Also called fine terra cotta or faience. It is available in a variety of colours and it indicates superior quality and is generally unaffected by adverse atmospheric conditions.
Advantages of terra cotta
- It is durable and relatively strong
- It is available in different colours
- It is cheaper than ordinary finely dressed stones
- It is easily cleaned
- It is fireproof and can therefore be conveniently used with RCC work.
- It is light in weight
- It is not affected by atmospheric conditions and acids and is capable of withstanding weathering actions better than most kinds of stones.
Earthenware
Indicate wares and articles made from clay which are burnt at low temperature and cooled down slowly. It includes sand and crushed pottery which largely prevents shrinkage during drying and burning. Earthen wares are usually soft and porous. When glazed earthenware become impervious to water and are not affected by acids and atmospheric actions. Earthenware is used to construct ordinary drain pipes, electrical cable conduits, partition blocks, etc.
Stoneware
Indicate wares and articles prepared from refractory clays which are mixed with stone and crushed pottery which are then burnt at high temperature and cooled down slowly.
Stoneware is more compact and dense compared to earthenware and are impervious to water, acids and atmospheric actions when glazed. A sound stoneware give a clear ringing sound when struck. Due to their durability and resistance to corrosive fluids they are quite popular in sanitary articles like wash basins, sewer pipes, glazed tiles, water closets, gully traps, etc. They are also used as jars to store the chemicals.
Porcelain
Porcelain is used to define fine earthenware which is white, thin and semi-transparent. It is also referred to as white ware due to its white colour. Clay of a sufficient level of purity and possessing a high degree of tenacity and plasticity is used to prepare porcelain. It is hard, brittle and non-porous. It is prepared from clay, felspar, quart and minerals. The constituents are finely ground and thoroughly mixed in liquid state, the mixture is given its desired shape and then burnt at high temperature.
Types of porcelain
- Low voltage porcelain – Prepared by dry process and is mainly used for switch block, insulating tubes, lamp sockets, etc. It can also resist high temperature on addition of alumina or silicate of magnesia.
- High voltage porcelain – Prepared from wet process and used as lining material in electric furnace, Insulators for high intensity current, vacuum tubes and spark plugs.
