Cold Casting - Metal

Introduction

Resin metal casting is a relatively simple method of creating quality metallic castings. Using pure metal in a fine powder form mixed with polyester resin and catalyst, they are usually produced from a latex or silicone mould.

See below, where we have explained the method to follow when creating a metal casting from a mould.

Safety Information

PLEASE NOTE: As with all chemicals safety procedures must followed. Correct PPE should be worn at all times.

THESE MATERIALS ARE UNSUITABLE FOR USE BY CHILDREN UNLESS UNDER SUPERVISION.

Preparation

Make sure your room is not too hot, or too cold! The ideal working temperature is around 20ºC. It’s not recommended to use resin in a domestic setting due to the smell, so a heated garage or outbuilding is ideal.
Prepare your mould using your preferred release agent – if you are using a silicone or latex mould, a release agent is not necessary.
Gather your materials, tools and PPE before you begin.

Materials Checklist

Casting Resin
Catalyst (included with purchases of resin)
Metal Powder
Mould
Release Agent (if required)
Fillite
Polishing and finishing equipment
Mixing Equipment
Brushes
PPE

Method

There are two main elements when creating a metal casting.

The outer shell
The infill

Applying the outer shell

First weigh out the resin, add catalyst at a rate of 2% and mix thoroughly (see our guide to Mixing Catalyst)
Next, add the metal powder at a ratio of 0.75 to 1 part resin. It is possible to mix different metals together for different effects. You are aiming for a thick, spreadable consistency.
The catalysed mix is then applied to the mould surface. If you are using a reversible latex mould you may find it easier to turn the mould inside out, paint on the resin/metal mix and then reverse. Alternatively, you can thin the mix and revolve the mould until the surface is covered. This method requires two coats to make sure the shell is thick enough.

Infilling

Once the outer shell has set (approx. 2 hours), mix the infill resin with catalyst at 1% by weight. Then add filler powder (we recommend Fillite for lower shrinkage and less heat generation), and mix. This should give about 30 minutes working time.
Pour into the mould in one or two layers (depending on the size of the casting) and leave to cure.

TIPS

Pigment the infill resin to the approximate shade of the finished casting, this will help disguise any thin areas in the metallic shell.
Small casts should be done in one go, with a resin/metal mix only.
For larger casts, the infilling can be in two or more layers; pebbles, metal or stones can be added which will not only save resin but also add weight.
While curing, the resin will get hot, so to preserve the mould it’s best to remove the casting before the exotherm peaks (when the resin is at its hottest).

Finishing and surface finishing

Allow the casting to fully cure for at least 72 hours. You can cut back with wire wool and finish with metal polish, or if polishing mops are available, cut and polish back with cutting compounds.

A coat of wax polish or clear lacquer will prevent tarnishing.

Antiquing can be achieved by painting on a spirit-based stain. Leave it to dry, then abrade and polish; shoe polishes can also be used.

As an alternative, graphite can be mixed to the resin. 5% - 15% by weight can be added depending on the shade required.

Castings can be treated chemically to obtain a patina, and patination can be fixed by wax polishing.

For some sintered metals, patination is not possible unless small quantities of other metals are added, e.g., Aluminium will need 10% Lead added, and Brass will require the addition of a small quantity of Copper or Lead. Follow with wax polish to fix the patina.

We hope you’ve found this guide helpful. If you’d like more advice, please call us on 01209 821028 or email us.