Dating jasperware wedgwood

Clay is a refractory substance; it will vitrify only at temperatures of about 2,900 °F (1,600 °C).If it is mixed with a substance that will vitrify at a lower temperature (about 2,200 °F, or 1,200 °C) and the mixture is subjected to heat of this order, the clay will hold the object in shape while the other substance vitrifies.Firing also protects the clay body against the effects of water.If a sun-dried clay vessel is filled with water, it will eventually collapse, but, if it is heated, chemical changes that begin to take place at about 900 °F (500 °C) preclude a return to the plastic state no matter how much water is later in contact with it.This forms a nonporous opaque body known as stoneware.When feldspar or soapstone (steatite) is added to the clay and exposed to a temperature of 2,000 to 2,650 °F (1,100 to 1,450 °C), the product becomes translucent and is known as porcelain.This ware was copied in petuntse (a feldspathic rock also called china stone), the latter being ground to powder and mixed with the clay.

Clay, the basic material of pottery, has two distinctive characteristics: it is plastic (i.e., it can be molded and will retain the shape imposed upon it); and it hardens on firing to form a brittle but otherwise virtually indestructible material that is not attacked by any of the agents that corrode metals or organic materials.Pottery, one of the oldest and most widespread of the decorative arts, consisting of objects made of clay and hardened with heat.The objects made are commonly useful ones, such as vessels for holding liquids or plates or bowls from which food can be served.In the Western world, porcelain is usually defined as a translucent substance—when held to the light most porcelain does have this property—and stoneware is regarded as partially vitrified material that is not translucent.The Chinese, on the other hand, define porcelain as any ceramic material that will give a ringing tone when tapped.

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