< VEGETABLE WAXES
MINERAL WAXES
Mineral waxes, which are often as not derived from hydrocarbon oils, are probably the most important group of waxes used in modern lost wax casting. Very few professional foundries use blends which do not consist wholly, or at least mostly, of mineral waxes.
There are two waxes from this group of particular interest to the art founder – the microcrystalline and paraffin varieties. Both of these waxes are obtained as by-products from the de-waxing of lubricating oils during the refinery fraction process. Paraffin waxes are extracted from the lighter high boiling point fractions, microcrystalline waxes form the heavier, lower boiling point fractions.
Paraffin wax (melting range circa 104-158°F [40 - 70°C]), is best known for it’s use for making inexpensive candles, though for commercial purposes the wax is supplied in block form. Paraffin wax is one of the least expensive waxes to buy, however it’s use in the studio or foundry as a usable product in it’s own right is somewhat limited. This wax cracks and crumbles too easily when modelled, additionally it’s ‘greasy’ surface makes the secure attachment of casting accessories like runners and risers very difficult. Artist’s are well advised to avoid un-blended versions of this wax for serious modelling or casting purposes.
Whilst unsatisfactory in it’s own right, paraffin wax is an important blend additive and is widely used in combination with other waxes. Paraffin wax is often blended with bees wax, especially for dental casting processes, it is also often added to microcrystalline wax in varying proportions for foundry use.
In the art foundry wax shop, the smaller crystalline structure of the microcrystalline waxes offers superior working characteristics over paraffin waxes. Some microcrystalline waxes are good enough for use straight ‘out of the box’, though in practice many professional founders blend the base product to some extent.
Most microcrystalline waxes are agreeably ductile and malleable for modelling at room temperature. With a melting range of circa 140-158°F [60-70°C], this falls between the typical temperature ranges of insect and vegetable waxes, offering the artist and founder a suitable compromise product for general use. Melted microcrystalline wax also tends to solidify over a broad temperature range. This is an important characteristic when slush casting reproduction moulds, where good handling properties at lower temperatures is a highly desirable feature of a wax or blend (a good casting wax should still be pliable at about 110°F [43°C]).
Other type of mineral wax include ceresin, montan, and ozokerite. Ceresin is an especially viscous wax that when blended, can inhibit the flow of a more fluid wax.
SYNTHETIC WAXES
Synthetic waxes are based on organic compounds such as polythene and polyexthylene. These materials are designed to mimic the characteristics of natural waxes. The advantages of synthetic waxes is that they can be produced under exacting laboratory conditions, and are therefore less prone to the vagaries of supply and quality which can affect some naturally derived products. Synthetic waxes can also be consistently inter-blended to achieve very precise working characteristics.
Synthetic waxes are marketed under a variety of proprietory trade names. These waxes may find their way into the art foundry if a workshop purchases their wax material as a pre-blended product or pre-formed casting attachment, otherwise this group of waxes are not commonly found in either the artist’s studio or foundry workshop.
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