What is Terracotta?

The terra means earth and the cotta means baked. hence the terra-cotta means the baked earth. It is a clay-based unglazed or glazed ceramic, where the fired body is porous. It is thus a type of earthenware or porous pottery made from local clay and glazed with glazes containing galena. It is soft enough to be scratched by a knife.

Terra-cotta army

•  Making of terra-cotta:-

          There are four distinct operations are involved in the manufacturing of terra-cotta:-

1. Preparation of clay
2. Moulding
3. Drying
4. Burning

• Preparation of clay:-

          For terra-cotta, the selected clay is taken. The clay should contain a slightly higher percentage of iron oxide, about 5% to 8% and the proportion of lime should be less, about 1% or so. Sometimes several variants of clay with high alumina content are taken and then to this mixture is added sand, ground glass, old terra-cotta or pottery. The addition of such materials gives strength and rigidity to the terra-cotta products and it prevents shrinking while drying. Such clay is made free from any impurities such as grit, pebbles, organic matter, etc. It is then finally crushed and pulverized. The water is added in the required quantity and the ingredients are thoroughly mixed with spades. Such wet clay is kept for several days in damp conditions for weathering and tempering. It is then pressed or kneaded in a pug mill and it is made ready for the next operation of moulding. The required quantity of colouring substance is added at this stage to obtain the desired shade of colour in the final product of terra-cotta.

• Moulding:-

          The clay is placed in moulds which represent the pattern or shape in which the product is to be formed. For terra-cotta work, special moulds of plaster of Paris or templates of zinc are used. The size of moulds is determined by keeping due allowance for shrinkage. The fine sand is sprinkled on the inside surface of moulds with a hand.

• Drying:-

          The moulds filled in with clay are kept for some days for drying. After this period, The articles of the terra-cotta are taken out from the moulds and they are allowed to dry further in a room or under a shed. The drying should be done carefully and slowly with proper control of temperature. The gradual drying helps in retaining the correct shape and size of the blocks.

• Burning:-

Muffle furnaces

          The dried products are then burnt in special muffle furnaces. a muffle indicated a box or a compartment of a furnace in which things can be heated without contact with the fuel and its products. A damper indicates a metal plate which is provided in an opening to regulate the draught, The dried articles are arranged in muffle and the temperature of the kiln is raised to about 1200 degrees centigrade. This temperature is maintained for about four days and the burnt products are then allowed to cool down in kiln for about five days. For getting the glazed products, the glazed materials should be applied by brush on terra-cotta products before they are burnt.