Introduction to bronze sculpture technology

Sculpture is one of the mainstream arts, and bronze sculpture is the main form of sculpture. Since bronze works have appeared in ancient civilizations around the world, they are also a symbol of world civilization. The earliest bronze ware appeared in the Mesopotamian region of West Asia between about 5,000 and 6,000 years ago. The bronze ware of China's Shang, Zhou and pre-Qin period was exquisitely made, and it is considered to have the highest artistic value among ancient bronze ware around the world. In modern times, Europe is the most advanced in bronze production technology, and the United States has created a unique bronze color glazing technology in the past 30 years, although many people still prefer the traditional bronze expression of Western Europe.

Bronze sculptures are made of bronze (an alloy of metals such as copper, tin and lead). As an alloy, bronze has the advantages of high hardness, low melting point, good metallic luster and corrosion resistance compared to pure copper. The technology of bronze casting is represented by the lost wax method (wax melting method). The main process of lost wax casting is: first, the sculptor creates a sculpture model, then goes through a series of processes to make a wax mold of the object to be cast with materials such as beeswax, and then coats the surface of the wax mold with refractory materials to harden it into a casting outer mold, so that the wax melts and flows out, thus forming a mold cavity; then the core or inner mold is made; then, the copper liquid is poured into the mold cavity, and the object to be cast is obtained after solidification and cooling.

Sculpture model: The sculptor needs to compose the picture first, and then create the prototype of the custom sculpture. The most commonly used prototypes of sculptures are plaster and clay, and marble and wood are also used to create prototypes. For example, American sculptor Barry Stein uses wood as the material for sculpture model creation. In a strict sense, the prototype of artistic creation is considered the original sculpture. The sculptor himself or according to the opinions of the cooperative publisher decides the total number of bronze sculptures to be produced in the end. Common ones are 8, 16, 30, 50 and 99. In Europe and the United States, it is also common to have more than 100 pieces, which depends on market demand.

Re-molding: The factory re-makes the silicone mold based on the model. From here on, it is usually the work of the copper foundry, but artists usually participate (mainly for supervision and quality control). The silicone mold is made by brushing silicone on the model layer by layer and letting it dry, and then dividing it into two halves to make a silicone mold.

Wax pouring: pour wax water (yellow wax or beeswax) into the silicone mold to form a wax shell

Wax repairing: polish the wax shell to ensure the perfect performance of the wax model

Shell making: pour slurry inside and outside the wax shell, attach high-temperature refractory slurry material to the wax model, and wait for the slurry to solidify, which is also called shell making. The domestic production process often uses sand to make sand shells, and most of the copper casting processes in Europe have abandoned sand materials, so that the surface of the final bronze work can be smooth and free of sand holes.

Dewaxing: Put the wax shell after slurrying into high-temperature steam, and the wax in the shell melts and flows out when it is heated. There will be space for the custom bronze statue shape in the shell

Firing: Heat the shell in a roasting furnace to about 800 degrees

Casting, heat the prepared copper to about 1000 degrees to melt, and cast it into the shell. The formula of bronze is one of the specialties of every copper foundry, which has a direct impact on the subsequent polishing and grinding.

Shelling: Use a high-pressure water gun to knock down the sand shell

Welding: There are metal rod brackets on the sculpture for fixing during the production process. At this time, it needs to be cut, and the process holes are formed on the sculpture after cutting. The process holes on the copper need to be welded.

Polishing and grinding: Polish the copper to make it bright. This process is through sawing, chiseling and grinding to eliminate excess copper blocks, burrs and flash.

Fine grinding and scrubbing: Wipe the polished copper parts to make them smooth. The sculpture needs to be finely polished and wiped again to get a yellow and flawless little copper man.

Hot coloring: Use chemical reagents to spray on the copper surface at high temperature, and form the desired color after heating. The high-temperature coloring process is actually a very important link in bronze sculptures, which directly affects whether the final sculpture product is qualified.

The last process is surface protection: The surface of the copper parts after coloring is sealed and protected with a protective agent to prevent oxidation and discoloration. This process is also suitable for the maintenance of sculptures at home. If there are no other materials, the maintenance wax of solid wood furniture can also be used.