Clay must usually be heated to about 60 °C before it is really pliable. Because most types of clay contain relatively large amounts of sulphur compounds and the crystallization point of sulphur is approximately 70 °C, there is always the danger when being heated that the sulphur will „sweat out“, deposit itself on the clay and in the oven and contaminate the ambient air.
The product TecClay, however, as a result of advancements to the well-known standard clay, is absolutely sulphur-free. A further important advantage of this product is its low weight – it is approximately 40% lighter than ordinary clay and therefore makes possible the transporting of even really large models. In addition, the pre-heating temperature of TecClay is much lower: from 50 °C to 55 °C. After being removed from a hot oven, TecClay retains the heat a lot longer than ordinary clay, a trait that makes it that much easier to work with by hand.
In comparison to standard clay, TecClay is more stable at temperature and its adhesion abilities are excellent: pre-heated TecClay, even when cut into very thin strips, will stick to a substrate without having to heat that surface with a hot-air gun. In order to attain a mirror type finish, this material can be polished with a cotton cloth or simply a blade – highlighting with film is no longer necessary.
Besides the already mentioned advantages, TecClay is just as good (or better) to work with than standard clay: it is absolutely odour-free, oxidation-free, homogenized (free of bubbles) and produces a very hard surface. As a result, its edges are extremely sturdy (hold up in a wind tunnel) and it lends itself to being milled. The removed material is dry and simply falls off of your tool. In addition, TecClay is very tough and tenacious with the result that trim strips or decorative mouldings can be securely attached to it using nails or screws. At temperatures from 1 °C to 20 °C, TecClay can be stored indefinitely.
Although TecClay is sulphur-free, it should still not be used for making moulds with addition-crosslinked SILICONE because TecClay contains iron oxide colouring material which itself has an inhibiting effect when it comes into contact with this type of silicone. We therefore basically recommend that any moulds made from clay models should only use condensation-crosslinked silicone because the risk of inhibition is substantially less. As an alternative, moulds can be made from clay models using plaster based materials or elastic PUR RESINS.
Among professional model makers the English term Clay refers to a special modelling material that will not dry out in the air and which can be machined at room temperature (15 °C to 25 °C). Clay (sometimes called Design Clay), then, is primarily used in the automobile industry for designing auto bodies. In order to keep costs and the weight of the model low, the rough shape made with the clay is transferred onto a base body made from RIGID FOAM (e.g. polystyrene foam) or wood. In the process, the clay, which is relatively hard at 20 °C, is pre-warmed in an oven heated to, depending on the clay, 50 °C to 65 °C so that it will become more pliable and easier to apply on the model.
After the applied clay has cooled off and thereby become hard again, it can, unlike normal plastiline, be machined. The desired shape is then slowly arrived at by means of grating or scratching. In industry, this work is done by a computer driven milling machine whereby the surface of the model is subsequently scanned again and retraced according to the CAD data. If too much material has been removed, warmed clay can be added to the surface after it too has been warmed by means of a hot-air gun.
In the automobile industry, finished model studies are usually overlain with very special films or paints so as to give the look of painted coachwork. If necessary, these special coatings can be removed in order to make any later changes in the shape. Modulor does not yet have these special materials in its product range - clay surfaces, however, can be also successfully treated with TONING PIGMENT or RESIN-DISPERSION INTERIOR PAINT.