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Introduction

This section covers most aspects of resin casting where clarity is not required. The basic requirements for successful casting are extremely simple and providing good sense and sensible working practices are observed there is no reason why you should not be able to produce satisfactory castings. Polyester resin are widely used to produce such items as chess pieces, statuettes, miniature cottages, museum replicas and for the “potting” of electrical components.


Polyester Resins

General purpose polyester resins are often used for simple low cost castings. Casting Resins have lower viscosity which allows higher quantities of fillers to be added. A variety of fillers can be added. Depending on the filler used, the mix may vary from 50:50, filler:resin, up to 70:30 filler:resin by weight. Both resins can be used unfilled for mini castings up to about 100g, castings above this size without filler are likely to crack and damage your mould.

Polyester resins are suitable for casting in a variety of moulds including silicone rubber, latex, polythene, fibreglass, glass, etc.


Fillers & Effects

A variety of effects and finishes are possible using a combination of fillers and colours, we list a selection:


Cast Stone

Hard wearing stone effects can be obtained by mixing various grades of sand, gravel, stone dust, etc., into polyester resin. Colour can be adjusted by using opaque colour paste.


Ivory

A good ivory effect can be obtained by tinting resin with a combination of white and ivory colour pastes.

A certain amount of trial and error mixing will be needed to obtain the best results. Scrimshaw (scratched designs on ivory or bone) is possible provided suitable originals and silicone rubber moulds are used. The use of various stains, especially brown, is important in obtaining an authentic ivory look.


Marble

A realistic white cast marble effect is difficult to obtain. Resin filled with marble dust and a little white pigment gives reasonable results. The addition of marble dust into water clear casting resin, however, gives excellent results, especially if this is used as a back up layer behind a white tinted gelcoat. If flexible moulds are being used without a gelcoat, however, extra catalyst will be necessary to effect a rapid tack free cure.


Resin Metal Casting

The use of sintered metals to give metallic finishes, is a popular and relatively simple process.


Casting Method

Described is a small chess set casting using casting resin and it is assumed that you have a latex mould ready for use. It is recommend that, because of the smell of the resin, it is advisable not to use this material in a domestic situation. A well ventilated heated garage or outbuilding is ideal. The working temperature should be around 20ºC (68oF). No release agent is required. Prepare pieces of card with a central hole to act as supports for suspending the mould when filled. Give the resin a stir but try not to introduce too much air. Pour about 200g of resin into a small container. This quantity of resin may fill several moulds.

See mixing catalyst chart for addition of hardener to resin.


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