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The defining mechanical property of clay is its plasticity when wet and its ability to harden when dried or fired. Clays show a broad range of water content within which they are highly plastic, from a minimum water content (called the plastic limit) where the clay is just moist enough to mould, to a maximum water content (called the liquid ...
A firing in a kiln to convert the unfired glaze surface to a glassy surface coating. Also called glaze firing. Greenware Unfired clay articles Grog See chamotte, above. Gum arabic A natural gum used as a binder to enable the glaze to increase the adherence to the body.
Fire clay is a range of refractory clays used in the manufacture of ceramics, especially fire brick. The United States Environmental Protection Agency defines fire clay very generally as a "mineral aggregate composed of hydrous silicates of aluminium (Al 2 O 3 ·2SiO 2 ·2H 2 O) with or without free silica."
Clay tempered with sand, grit, crushed shell or crushed pottery were often used to make bonfire-fired ceramics because they provided an open-body texture that allowed water and volatile components of the clay to escape freely. The coarser particles in the clay also acted to restrain shrinkage during drying, and hence reduce the risk of cracking.
The earliest ceramics made by humans were fired clay bricks used for building house walls and other structures. Other pottery objects such as pots, vessels, vases and figurines were made from clay , either by itself or mixed with other materials like silica , hardened by sintering in fire.
In the making of firebrick, fire clay is fired in the kiln until it is partly vitrified.For special purposes, the brick may also be glazed. There are two standard sizes of fire brick: 9 in × 4 + 1 ⁄ 2 in × 3 in (229 mm × 114 mm × 76 mm) and 9 in × 4 + 1 ⁄ 2 in × 2 + 1 ⁄ 2 in (229 mm × 114 mm × 64 mm). [2]
Making fired bricks is an advanced pottery technique. Fired bricks are solid masses of clay heated in kilns to temperatures of between 950° and 1,150°C, and a well-made fired brick is an extremely durable object. Like sun-dried bricks, they were made in wooden molds but for bricks with relief decorations, special molds had to be made.
Through the addition of balanced temper, the clay could be made "more malleable and stable during production, and also more porous, which made it easier to dry, bake, and use the finished vessel." [14] After the clay had been mixed with water it would be full of air bubbles. To prevent cracking during the firing process, the clay had to be kneaded.