Modelling clay

Modelling clay is any of a group of malleable substances used in building and sculpting. The material compositions and production processes vary considerably.

Ceramic clays are water-based substances made from clay minerals and other raw materials. They are baked at high temperatures in a process known as firing to create ceramics, such as terra cotta, earthenware, stoneware, and porcelain. Paper clay produced by pottery clay manufacturers is a clay body to which a small percentage of processed cellulose fiber has been added. When kiln-fired, the paper burns out, leaving the clay body. Consequently, the firing temperatures and glazes selection should be the same on those used with the clay body.

Oil-based clays are made from various combinations of oils, waxes, and clay minerals. Because the oils do not evaporate like water, oil-based clays remain malleable even when left in dry environments for long periods. Articles made from oil-based clays cannot be fired, and thus are not ceramics. Because rising temperature decreases oil viscosity, the malleability is influenced by heating or cooling the clay. Oil-based clay is not water-soluble. As it can be re-used, it is a popular material for animation artists who need to bend and move their models. It is available in a multitude of colors and is non-toxic.

Oil-based clays are referred to by a number of genericized trademarks. Plastilin, which was patented in Germany by Franz Kolb in 1880, was developed by Claude Chavant in 1892 and trademarked in 1927.Plasticine was invented in 1897 by William Harbutt of Bathampton, England. Plastilina is trademarked as Roma Plastilina by Sculpture House, Inc. According to their website, their formula is 100 years old. Roma Plastilina contains sulfur, and since certain moldmaking compounds do not set in sulfur's presence, making molds of items made of industrial plasticine is difficult. In India, oil-based "No Sulphur" clay is manufactured by Uday Industries for industrial, as well as retail use.

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