< MINERAL & SYNTHETIC WAXES
WAX BLENDS
Although some of the waxes mentioned in the preceeding pages can be used without modification (MICROCRYSTALLINE and SYNTHETIC products are typical of this), many sculptors, founders and other professionals who use wax blend the basic supplied product. Often, art foundry wax blends remain a closely guarded commercial confidence, so unless a potential user already knows the constituents and proportions of a suitable blend, their usual options are to either purchase a pre-blended product from their founder, art store and commercial supplier, or else develop their own personal selection. The advantage of developing a range of personal wax blends is that the user can, over time, refine a wax or range of wax products to suit their exact needs, be it modelling, slush casting, repairs, gluing, protective, polishing and so on. A blend can also be modified to allow for changeable conditions, seasonal variations in ambient temperatures for example, when the user can create a soft version of a wax for winter use, a harder version for the summer [ref 1].
Prior to the wide availability of mineral waxes, foundry waxes were typically composed of BEES WAX blended with fine turpentine (about 4 parts wax to 1 part turpentine), or else beeswax blended with quantities of liquid paraffin and resin. Research carried out at the National Gallery in London, using infra-red absorption spectrometry techniques on various samples from the Victoria and Albert Museum collections [ref 2], revealed that the majority of tested waxes were composed simply of beeswax with a small quantity of added natural resin.
Today, MINERAL WAXES are excellent and form the basis of most foundry waxes, it is quite possible to use a good quality microcrystalline wax for foundry work without any additional blending whatsoever. In practice founders nearly always modify supplied wax. At the very least adding a dye or other colouring agent to SIGHT the wax (see ADDING A COLOUR).
Paraffin wax is a common additive to foundry waxes, though products containing microcrystalline and paraffin waxes alone can lack cohesion, so this blend is often improved by adding in a small quantity of a resin (rosin or gum dammer), polythene, or a quantity of sticky wax. Other waxes that might be found in a foundry blend include bees (insect), ceresin (mineral) and carnauba (vegetable) waxes. When added to a microcrystalline base, these waxes will variously influence the working characteristics of the blended product, soften or harden, adjust the melting range, flow rate, viscosity and so on.
Dyes, resins and plastics have already been mentioned as potential non-wax additives to blends. Again, the precise effect adding in these various materials will have on a particular blend will depend upon the nature of the base wax product and the proportion of added material. The following list includes many of the more common non-wax additives and their function within a blend.
RESINS: Pine, dammar, kauri, rosin etc. Tend to harden and increase stickiness.
OILS/PLASTICS: Petroleum jelly, hydrocarbon oils, PVC monomeric plasticisers (plastic food film). Tends to soften a blend, increases plasticity.
SOLVENTS:Turpentine etc. Softens wax, alcohols are used to clean and degrease surfaces.
FILLERS: Isopthalic acid, bisphenol, polystyrene. Modifies a blend’s ‘body’.
SILICONE: Improves polishing and lubricating qualities.
ADDING A COLOUR TO WAX >
|
|
