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Clay is a type of fine-grained natural soil material containing clay minerals [1] (hydrous aluminium phyllosilicates, e.g. kaolinite, Al 2 Si 2 O 5 4). Most pure clay minerals are white or light-coloured, but natural clays show a variety of colours from impurities, such as a reddish or brownish colour from small amounts of iron oxide .
Hexagonal sheets of the clay mineral kaolinite (SEM image, 1,340× magnification) Clay is a very fine-grained geologic material that develops plasticity when wet, but becomes hard, brittle and non–plastic upon drying or firing. [2] [3] [4] It is a very common material, [5] and is the oldest known ceramic.
Once conditioned, the clay will remain pliable until the particles eventually re-adhere. [8] Oven-hardenable PVC plastisol, "liquid polymer clay," is a complement to polymer clay that can be used as an adhesive to combine pieces, or to create various effects. Pigments, chalk pastel, and regular polymer clay can be added to make colored liquid clay.
Rammed earth is both an old and newer take on creating walls, once made by compacting clay soils between planks by hand; nowadays forms and mechanical pneumatic compressors are used. [10] Soil, and especially clay, provides good thermal mass; it is very good at keeping temperatures at a constant level. Homes built with earth tend to be ...
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.
Clay wall plaster exhibited very high deposition velocities and negligible yields. Clay and materials containing clay (e.g. bricks) consume ozone readily, perhaps because of a reaction catalyzed by metals present in the clay. Clay plaster with very high ozone uptake rates, has certain surface roughness, and porosity.
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Montmorillonite, a member of the smectite group, is a 2:1 clay, meaning that it has two tetrahedral sheets of silica sandwiching a central octahedral sheet of alumina. The particles are plate-shaped with an average diameter around 1 μm and a thickness of 0.96 nm ; magnification of about 25,000 times, using an electron microscope, is required ...