The sculpting process involves 10 steps:
1. Modelling the sculpture in modelling wax
First, sculptress Elly Hendrix models the sculpture in modelling wax. This kind of wax can be compared to butter: dependent upon its temperature, it is hard or soft, and it is possible to melt the wax. The modelling wax is of a dark colour, so that the shape is clearly visible. By gradually adding and removing parts, the wax model grows.
2. Applying a stone mould around the wax model
Then Elly mixes gravel, gypsum and water in a bucket. She stirs it until it has the thickness of porridge and is free of lumps. On her worktable she immerses the wax model in the mixture. She applies a layer of fireproof stone on top and levels it. At a later stage, the wax will be melted and will need to flow from the mould. Yet in some places, it may not be possible for the heated wax to escape. Therefore, Elly also adds little wax sticks to create channels in the mould through which the heated wax may still flow out. Also, at one side, the wax model sticks out of the mould; this is where liquid bronze will later be cast into the mould.
3. Melting the wax model
At the foundry, the bronze founder places the stone mould with the wax model inside it in an oven, with the wax channels running downwards. A brick underneath the mould will allow the modelling wax to flow out freely. When the oven is loaded, the door is closed and the oven is heated up to a temperature of 700 degrees Celsius. After two days, all modelling wax will have flown from the mould. What remains is the stone container.
4. Jamming the mould
The bronze founder then places all stone moulds with their holes upwards in an iron holder. He fills up the spaces in between the moulds with Brussels earth and tamps it with a pneumatic hammer so that the earth becomes rock-hard and the stone moulds become jammed. He covers the openings in the moulds with a newspaper, to prevent filth from falling in.
5. Filling the mould with bronze
The melting pot, filled with 120 kg of massive bronze, is heated in a round forge. After 3 to 3½ hours, its temperature will have risen to 1030 degrees Celsius, and the bronze will be ready to be cast. At that point, founders raise the pot from the oven, place it in a holder, hoist it, and guide it to the stone moulds. They cast the liquid bronze into the openings of the moulds and let the bronze cool down and solidify.
6. Taking the stone moulds out of the holder
The iron holder is removed, after which the sand subsides.
7. Cracking the moulds
While the stone moulds are still warm, they are taken outside. After the bronze has cooled down, the founder smashes the moulds. The bronze castings are taken out.
8. Water spraying
With a high-pressure sprayer, the last stone remnants are sprayed off of the bronze.
Each rough bronze casting will still need to be chased. With big grinding equipment, Elly removes the surplus of bronze from the sculpture. With fine drilling instruments and dentist equipment, she brings back the details. The form of the sculpture is now identical to the original wax model.
Acid and fire will give the bronze its final colour. On her balcony, Elly has a fireproof table where she places the sculpture, heats it with a roofer’s burner and applies acid to it with a brush. By heating the sculpture, its colour changes from green to black. The bronze’s surface now holds an etching layer. After letting the bronze cool down, Elly cleans the sculpture with water, dries it under a hair dryer, and treats it with antique wax that melts on the warm sculpture. Finally, she brushes the surface, so that the etching layer becomes thinner and colour nuances come about.