latex rubber

LATEX

Latex is extracted from the tree species ‘Heva Brasilensis’ by tapping the trunk and collecting the secreted material. In it’s natural form, latex lacks tensile strength, but it will adhere tenaciously to most surfaces. Latex for commercial use is modified from the raw material, usually by mixing with a water based colloid (for more on colloids see INVESTMENT). Latex for moulding is supplied as a ‘one pack’ product, which needs no catalyst or other additive for use. Latex is usually applied by brushing the rubber directly thin layers over a master pattern treated with a good release agent. Each layer is permitted to air dry before applying the next. Large surface areas of painted latex can be reinforced by laying in coarse fabric sheets between layers of rubber. Later, after curing, the latex blanket can be supported by an overlaid plaster case.

Once cured (by exposure to air or oven assisted), latex produces a very tough mould – especially well suited for use as SKIN MOULDS. Skin moulds are most familiar as inexpensive childrens' toys that enable plaster to be poured into a mould, which then sets to the shape of a cartoon character and the like. Once the plaster has set, the latex can be peeled back and turned inside out to eject the reproduced image.

Latex can be used to produce waxes for metal casting, as well as plaster, resin and concrete reproductions. Latex is prone to severe shrinkage and can be adversely affected by exposure to ultra-violet light, oil and solvents. The supplied product usually has only a limited shelf life and is not suited to lengthy storage before use.

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