Lost and Found: thoughts on lost wax bronze casting

All my life as an artist I have asked myself: What pushes me continually to make sculpture? I have found the answer. Art is an action against death. It is a denial of death. Jacques Lipchitz 1891-1973

The idea of casting in bronze has roots that stretch back over 5,000 years. Fire’s power to destroy became a force for creation when Sumerian metalworkers discovered the alloy and developed their technique. Bronze weapons and tools were revolutionary in their efficiency and brought about enormous cultural change, but bronze also became a means of communication through symbolic objects. It became the vehicle whereby human instinct to create enduring records, signifiers of culture and experience representing a defining moment in history could be recorded.

Fundamental casting techniques are relatively unchanged. Early bronze sculptures were modelled in wax over a core of earth or clay, coated in more layers of clay leaving apertures for wax and air to escape and then baked until the wax melted – was ‘lost’. Molten bronze, poured into the opening at the top of the fired clay mould, filled the perfect negative which the wax had left behind.

Apart from advances in infrastructure and supporting materials the principle remains the same. Other methods have been developed such as sand moulding, ceramic shell and vacuum casting but lost wax block investment (to give it it’s full descriptive title) is still chosen by many artists and foundries as the best and most precise method of casting, particularly of small or complex works.

It’s thought the idea of editions was introduced by the Romans, creating moulds probably made from gelatine around original works in stone or clay. These moulds would have lasted long enough to create an edition of six to ten works before perishing. Gelatine was used until fairly recently for mould-making but has in the main been replaced by silicon rubber and plaster; besides not lasting very long the stench of rotting gelatine can’t have helped.

Flexible rubber moulds need to be held in place so are encased in plaster. For a small piece the mould is usually made in two halves, for larger works it’s made in several sections. Once the rubber is set around the original artwork the halves or sections are carefully prised apart and cleaned. This is the first of two negatives.

Wax is melted down and carefully painted into the moulds precise negative impression. A few coats are built up until the wax layers are robust enough to be joined into a positive and then modelled, using the original artwork as reference. Smaller waxes are usually hollow but larger works are given a core of loose grog mixture.

A more solid wax is used to create fine, tubular runners and risers which are carefully welded on to the wax model, creating routes for air and wax to flow once the wax is surrounded by its second, clay mould. Comprised of plaster and grog, this clay slurry is painted and flecked around the upside-down wax, building layers until it looks like a large, grey boulder with a hole at the top.

Left to dry for a few hours or overnight, the clay mould is put into the kiln while still slightly damp and baked for hours, until the wax has been lost and the perfect, second negative remains hidden inside.

Once the bronze has been poured into the clay negative and left to cool, the clay must be removed. This is not as easy as it might appear and can be one of the grimmest jobs in the foundry. A combination of jet washing and knocking out with tools usually frees it, or the process can also be done mechanically to an extent. Metal chasing is a skill and needs intense patience and concentration, to clean up the surface of the newly emerged bronze sculpture and tease it into an exact replica of the artist’s original.

The final stage in the creation of a bronze artwork is its surface: what does the artist envisage? Founders tend to develop their own recipes for patinas. It’s a tricky and often imprecise pursuit as chemicals react with each other, the bronze surface and the flame used in their application. Some people just want their work polished.

One contemporary artist answered the question of ‘how do you want it to look?’ with ‘like plastic’ – so it was painted, creating an interesting and unexpected contradiction and setting a precedent.

The development of symbolic thinking, of a consciousness extending beyond immediate needs to encompass reflections, memories and perceptions of future possibilities is really the foundation of creativity and art. Art is where bronze’s relevance remains, even now to cast something in bronze is to imbue it with huge significance, creating permanence through the use of temporary materials. An object – a message – that will last more-or-less forever.