To cast a bronze sculpture, two different techniques are used. What both have in common is the need for
an original model. It can be made of clay, wax, plaster, stone or metal. The casting usually is carried out with the help of cire perdue (lost wax) or sand casting.
Bronze is one of the world's oldest alloys produced by man. Articles were cast 5,000 years ago, and the cire
perdue technique was incredibly advanced at an early stage. Moulds were mostly used to make different
types of tools in the beginning. In the 19th century so-called sand casting/one-piece moulding came into
being using "hard sand" suitable for the casting of larger sculptures.
To a large extent, the craftsmanship looks the same today.
Procedure:
If necessary, the sculptor's plaster model is sawed into pieces and placed in moulding sand. Processed hard sand is placed around the model so that it
will not get stuck when it later is to be extracted from the mould. Vents are made in the sand to create various channels for air and for the molten metal that later will flow into the mould. Hard sand is again
put on top and then a cover is placed on the mould and the frame is turned over. In the next step the moulding sand and the plaster model are removed.
You now have a precise impression of the plaster model. A layer of plasticine is put in place that is the same thickness as the bronze will be.
An inner core of hard sand is formed to create a cavity in the sculpture, which is fastened securely. The plasticine is removed, the frames with front and back sides are put together and the mould is ready for the molten metal.
Molten bronze with a temperature of 1030-1100 degrees C. is poured into the mould, and the bronze finds its way down through the channels prepared in
advance. The bronze hardens, the mould is opened, the sand mould is broken apart (the so-called "lost mould") and the bronze appears.
After the sculpture is cast, all of the casting channels through which the bronze flowed are cleared away
and the sculpture is cleansed of sand and other residual materials.
Subsequently, the parts of the sculpture are joined together and the work is patinated (treated with salts,
acids and other chemicals) to create the desired hue. The sculpture goes through several polishing stages
and is now completely ready for delivery.