How to / FAQs

When you are using, say, Solid Cast 606 epoxy resin, which typically requires a post cure of four to six hours in an oven, larger objects can simply be placed under a table or some larger framework, draping over with a plastic tarp or blanket.

To do this, dust the mould with iron powder. From there, colour the casting mix to a rusty brown colour with acrylic paint pigment. Then, pour in the casting material. Upon removing the casting, dust down, then spray diluted hydrochloric acid onto the gray iron powder surface. Lastly, let sit for 24 hours. The resulting casting will have a rusty-iron look (all over) – combining a mixture of actual rust and rusty-coloured material in some background areas.

Beyond this particular look, the following method applies for any cold-cast material. In turn, optimum results are achieved by using a leafing-grade metal powder (in other words: a metal powder that transfers a full metal powder coating onto an item dipped into the powder). Very simply, use a dry brush to paint the mould surface in metal powder. Then, mix the powder into the casting material to achieve the same colour. From there, pour the casting material in. Upon removing the casting, buff the surface with a soft cloth. the overall look will be a low-sheen metal effect.

To do this, colour the casting material with an opaque pigment.

Epoxies, in particular, are very temperature sensitive. A temperature drop to 15°C (or lower) overnight will kill off cross-linking of the mixture. In turn, resins need to be consistently kept at 20°C (or more) for the entire cure period. Uncured epoxy resins may respond to later application of extra heat, but some may never revive and, in turn, will remain sticky. If this happens, you can wash off with warm, soapy water, dust it with talc or apply more resin mix to bond the sticky surface.

This typically indicates that the mould has reached the end of its life, so to speak, particularly where small pieces are starting to tear away. In turn, the casting life of a particular mould varies depending on the number of casts that have been made from it, the type of casting material, as well as the overall complexity of the object and, in turn, the mould, itself.

Generally speaking a vacuum pump is your best bet. Beyond this, there are several steps you can take to reduce the likelihood of bubbles. Firstly, mix materials in a steady figure-8 manner, ensuring that you mix the material on the mixing container sides. In turn, avoid lifting the material on the mixing container sides (and avoid lifting the mixing stick up and down). Then, pour the mixture out by pouring close to the work (and from one point). Slowly lift the mixing vessel to about 40cm above the work, and be sure to pour in a very thin stream (this will ensure that any air bubbles present are torn open as the material pours). In particular, avoid lacing the material over the work as this captures air. Keep pouring from one point, letting the mixture flow out evenly over the work like a slow wave.

The key thing is undercuts. The object shouldn’t be so complex that your mould halves (or multiple sections) can’t be withdrawn without excessive undercuts – a ‘tree’, for example, is to delicate to be able to practically cast.

Generally speaking, you need to allow adequate time to dry an organic object, just to ensure it’s thoroughly dry and devoid of moisture. In turn, not doing this will mean that it could decay and rot within the resin once the exothermic reaction takes place. The other consideration to take into account is that moisture will inhibit the resin cure.

It’s possible that air could have been present in the object you’ve embedded. In turn, warmth generated when the resin is setting causes the entrapped air to expand and, subsequently, create bubbles in the resin. A dried insect, for example, can still hold air in its body. Here, once the resin has been exothermic, the air will draw out. your best bet is to pre-seal the object with a thin coating of resin first. From there, let it fully dry, then embed the object.