Description
Beautiful and expertly crafted bronze sculptures from Indonesia. Some sculptures are hand-painted by artisans after the casting process in fantastic colors that truly capture the imagination.
There are several possible methods and procedures for casting bronze. The following attempts to provide an overview of the basic steps. A model is made, usually of wax, but if a rubber mold is made from it, it can also be made of clay, plaster, synthetic material, or even wood or stone. The wax used for this is typically casting wax, paraffin, or modeling wax.
For small wax models, the caster can proceed directly to the next step. For larger models, or for models made of clay or plaster, for example, a hollow wax model must be made first. To this end, the caster usually makes a rubber mold with a plaster support cap, which ensures that the rubber mold retains its shape.
Various materials, such as casting wax or plaster, can be cast into this rubber mold at relatively low temperatures. In this case, a hard wax casting is required that is already at the thickness of the final bronze. Above a certain thickness, it becomes difficult to cast bronze in a solid form due to uneven shrinkage of thicker and thinner parts. The foundryman pours liquid wax into the rubber mold until a layer of wax of the correct thickness has solidified inside the mold. The remainder is poured off, creating a hollow wax casting. This (hollow) casting is fitted with wax protrusions that will later serve as casting channels for the supply of bronze and venting channels for the removal of air from the mold. The wax casting, including the channels, is covered inside and out with a refractory mass. This can be a mixture of gypsum and chamotte or another shrinkage-resistant and refractory material. Stainless steel core supports ensure that the distance between the core and the outside remains constant. The finished mold is heated in an oven for an extended period to melt out the wax and remove all moisture from the mold and, if it is made of gypsum, also all chemically bound water. A dry mold has now been created with a cavity in the shape of the model containing casting channels. Liquid bronze is poured into this. After cooling, the channels are sawn away and the casting is finished: burrs and protrusions are ground away, and holes and unwanted cavities are hammered shut or welded. To protect against oxidation and for aesthetic purposes, a layer of patina is often applied to bronze castings using chemicals—a process known as patination.
