Modelling clay
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Clay has been used for modelling from the beginning of civilization. The original earthen clay used by modellers and seemingly forgotten by those who use more recently developed products is dug from the ground. Colours vary from bright red, yellow, terracotta and cream to black. Classically, terracotta was the preferred material; it is still very popular. Modellers also prefer grey which dries light grey and then can readily be painted. Earthen clays can be fired but are often air-dried. In layman’s terms it is made up of very finely grained hydrous silicate particles which is technically described in Clay.
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[edit] Nylon Reinforced Clay
A relatively new product variation of earthen clay is clay reinforced with filaments of Nylon. It is used by modellers who do not intend to fire their works. This is designed to bond the clay more tightly and therefore reduce the incidence of cracking. Modelling large models with earthen clays is made difficult because clay shrinks unevenly when it dries. It is therefore essential that the model is dried very slowly otherwise fatal cracking occurs. Cracking can also be minimised by using an internal supporting frame (armature) of wood, wire mesh, polystyrene or similar materials made to the rough shape of the intended object and then finishing the model with a layer of clay no more than 15 mm thick.
[edit] Firing Earthen Modelling Clay
Modelling clays both natural and Nylon reinforced can be fired at a kiln temperature in the range of 1000 °C to 1250 °C. When firing a model, modellers should take care to ensure that their armature (frame) can withstand these temperatures without breaking down or releasing explosive or noxious fumes. Models can then be glazed in the same way as pottery clay. The Nylon does not affect the glazing process.
[edit] Plasticine
Whilst earthen clay has many advantages, not least that it can be reworked and resoftened after drying, it has notable disadvantages namely that it dries out unevenly and relatively quickly, it cracks when used in thick sections, it is not easy to re-work, it requires high temperatures to fix it permanently, it can distort as it shrinks and it is brittle.
As a result of this during the last hundred years or so, artists and craftsmen have sought out other materials.
Notable amongst these is Plasticine which was invented by art teacher William Harbutt of Bathampton, near Bath, England in 1897. He wanted a non-drying clay for use by his sculpture students. Plasticine has since become a generic term, especially in the Commonwealth. The great advantage to artists of Plasticine is that it is very slow drying, it is not soluble in water as it is oil based. When warmed to between 30 and 40 °C (body temperature), it is easily workable. It is an ideal material for animation artists who need to rework their models. It can be reused. It is available in a multitude of colours. When cooled to room temperature of say 18 °C. It stiffens and is very stable. It is non-toxic and is therefore suitable for use by children. There is now a variety of similar products. Notable amongst these in the UK are Newplast and Colour Clay.
Generic Plasticine being readily workable in fine detail is also suitable for creation of an original work from which a mould (molding)can be made. Castings and reproductions in a much more durable material can then be produced.
[edit] Polymer Clays
Some modellers and craftsmen want a modelling material which hardens permanently at low temperature without significant distortion. Polymer clay is the solution. Polymer clay hardens by curing at temperatures created in a typical home oven generally at 265 to 275 °F (129 to 135 °C) for 15 minutes per 1/4" (6 mm) of thickness and does not shrink or change texture during the process. When properly cured, most items won't break if dropped or normally stressed. Polymer clay also comes in liquid form and in permanently flexible solid form. Polymer clay is sold in craft, hobby, and art stores, and is used by artists, hobbyists and children. Leading brands of polymer clay include Premo, FimoClassic and FimoSoft, Kato Polyclay, Sculpey Cernit, Formello and Modello and Das.
[edit] Wax-based Clay
A modelling clay based on a mix in various proportions of wax and ceramic clay. Commonly used while developing car designs.
[edit] Paper Clay
There are two major groups of paper clay/paperclay users.
There are those using paperclay as an unfired body and those using paperclay in the studio ceramic studio to make sculptural and functional ceramics.
Studio ceramics and paperclay.
Airdrying modeling clay. Commercial air drying clay does not shrink noticeably when drying. This paper clay can be painted, varnished, drilled, sawn, cut and glued. This makes it a great, fun product for children and an extremely versatile and challenging product for fine artists. There is brand of paper clay called Fun Fair Paper Clay which is aimed at children. Model Magic by Crayola is a similar product.
