Ciré perdue

Although the lost wax method of casting is thousands of years old, for many it is becoming a lost art. In Northern Ireland, Graham Harron is the only goldsmith who consistently casts his own jewellery using ciré perdue, or the lost wax method.

When the first metalsmiths found their material in the ashes of a fire, they discovered that it retained the shape of the ground on to which it had spilled. All subsequent casting technology has developed from this beginning. We know of highly sophisticated bronze castings made in China about 7,000 years ago and, soon after, the Egyptians evolved highly developed casting skills, creating stunning work that has inspired generations of metalsmiths.

Compared with most enterprises, casting has changed very little in the last 4,000 years – the materials and scale have grown, but the process is virtually intact. The adoption of the method for producing dental castings by the lost wax process was first introduced in 1907 and techniques developed for dental work were taken up by the jewellery trade in the 1940s.

Most of the casting developments relate to large-scale assembly line production and do not benefit the hand craftsman. In manufacturing, casting is one of many processes used to duplicate a shape – the manufacturer chooses a method that will create the largest volume of the best product at the minimum expense.

For the individual craftsman, like Graham, working on limited production or individual exclusive pieces, it is normal to work on a piece under one’s own hands from start to finish. This type of work has an emotional reward for the maker and allows modification of the three-dimensional wax model before casting, allowing the craftsman more creativity in designing the piece. Creative hands-on design, combined with the ability of the lost wax process to produce consistently clean castings, means that finished pieces are not only beautiful, but strong and durable.

Creating an individual piece

A three-dimensional model is made using various types of wax, depending on the piece being designed: soft wax, carving wax, sticky wax, or wax wire. The model is then mounted on a sprue, or wax rod, using a soldering iron and the sprued model is mounted on to a base and fitted with a watertight section of pipe called a flask.

A plaster-like material called investment is mixed to a creamy consistency, taking care to remove any bubbles from the mix, and poured over the model to fill the flask. The investment is dried and then burned out in a kiln to remove all traces of the wax model – hence the term ‘lost wax’. This leaves the craftsman with a mould of the piece.

While the mould is still warm from the burnout, molten metal is poured into the mould, where it assumes the shape of the original model. After brief cooling, the mould is quenched in water to break it and release the casting. The cast piece is then finished before being polished. If the piece includes precious or semi-precious stones, these are set in place after polishing.