Polyester resins and finely ground metal powders can be combined to produce very realistic simulations of metal castings. The basic requirements for successful casting are extremely simple but tend more to be an artistic process rather than an engineering discipline.
The best, most realistic effects are obtained by mixing as much metal powder as possible into a gelcoat/resin mixture but from an economics point of view the normal mixture for copper based metals is 3 parts metal to 1 part resin by weight.
Many castings will have undercuts and therefore require the use of flexible moulds which can be made from silicone rubber, latex rubber or PVC compounds, while rigid GRP moulds can be used if undercuts are not present.
A Suggested Casting Procedure
1. Calculate quantities required. Allow 600-1000 grams gelcoat/resin per M2 and allow 1800-3000 grams metal per M2
2. The viscosity of the gelcoat determines the amount of metal that can be combined with it and the ease with which the gelcoat/metal mixture can be brushed into the mould surface detail. A good compromise is to make a gelcoat/resin mixture by combining equal parts of gelcoat and non-waxed laminating resin, e.g.