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 Casting
part is done using a mold. Resin jewelry 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.
Resin jewelry 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.
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 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 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 jewellery or even art objects because of their odor
that never goes.
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.
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