Resin Jewelry Casting

Resin is quite a versatile media for jewelry and decoratives. It can be cast in the desired shapes using the moulds. It can be painted or cast in the desired color. Certain qualities of white resins are used to make imitation jewelry. The finished product resembles ivory. By careful molding the resin is able to imitate almost all the characteristics of the scrimshaw. Due to all these qualities along with its lightness and affordability it is quite popular fashion jewelry base material.

Process
Casting part is done using a mold. Resin is generally cast as a pourable liquid or it can be "laid up"; laminated by hand with reinforcing cloth of glass or carbon fiber. Most of the resin can be cast using flexible molds of polysulfide and urethane. Rigid molds of plaster, fiberglass, metal or wood are also used. Usually a separator coat is applied to the molds so that the resin can be separated with ease after hardening. Silicone molds are the most convenient and appropriate as they are flexible and need no separator coat.

Types of Resins
The casting resins can be acrylics, polyesters, urethanes, and epoxies. Each type requires some special treatment while molding.

Polyester Resin - Polyester resin is the most commonly used resin. Most figurines are cast in this. It forms the component of most fiberglass lay-ups and is normally glass clear but with a green tint. It can be filled for thicker castings and to affect its appearance. It can be tinted in various transparent and opaque colors using special pigments. Polyester resin comes in both laminating [hot-promoted] and casting [slow promoted] formulas.

The hazard is that the polyester resin stinks while casting. The smell can be noticed in the newly cast products. Though it goes off with time. Also the process is toxic because of the use of cross-linking agents and catalysts, dilutants, and accelerators.

Epoxies- Epoxies are much more expensive than polyesters. Epoxies have better temperature tolerance than polyester and are stronger. The epoxy compound ingredients are mixed in different rations to create different formulations. They can be tinted or colored with various pigments in opaque and almost transparent colors. They produce the least odor amongst all resins.

Urethanes - Urethanes are wide application resins that can be molded to flexible to rigid forms. Earlier they had a yellowish to tan color but now they can be pure white or even transparent. They are not brittle like other qualities. They are not usually used for jewelry or even art objects because of their odor that never goes.

Caution
The polymerization process (converting from liquid to solid state) is an exothermic reaction, the resins emit a lot of heat and tend to shrink. This causes casting defects the center solidifies and generates heat faster than the surface touching the mold. As the resin shrinks, its sticky surface detaches from the mold leaving a rough surface called. This problem has to be tackled with while resin casting.