Lost-wax casting

Artists can make beautiful metal art.

First, they make a shape out of wax. Next, they cover the wax in a hard shell. They use heat to melt the wax away. This leaves an empty space inside the shell.

Then, hot liquid metal is poured into that space. Once the metal cools, it stays in the new shape. This way, artists can make very detailed pieces.

People have used this trick for a long time.

Artists use a special way to make metal art. It is called lost-wax casting. This method lets them make very detailed shapes.

First, an artist makes a model. They often use soft wax or clay. Next, they make a mould, which is a hollow shape. This mould fits perfectly around the model.

Then, they pour melted wax into the mould. This makes a hollow wax copy. They take the wax copy out. They add wax tubes to it. These tubes act like paths for metal to flow.

Next, they dip the wax into a liquid called a slurry. This makes a hard shell. They heat the shell in a kiln. The wax melts and runs out. This leaves an empty space inside the shell.

Finally, they pour hot, liquid metal into the shell. Once the metal cools, they break the shell away. The metal stays in the shape of the original wax. This trick is very old. Some gold pieces are 6,500 years old!

Lost-wax casting is a special way to make metal art. It is also called investment casting or precision casting.

This method lets artists create very detailed shapes. They can use metals like gold, silver, brass, or bronze. It is a way to make a metal duplicate of an original sculpture. This process is very important for making intricate works.

The way it works involves many careful steps. First, an artist makes a model from wax or clay. They then make a mould around that model. This mould is a hollow shape that fits the model perfectly.

Next, they pour melted wax into the mould to make a hollow wax copy. They add wax tubes to this copy to create paths for metal.

Then, they dip the wax into a liquid called a slurry. This creates a hard shell. When they heat the shell in a kiln, the wax melts and runs out. This leaves an empty space inside the shell. Finally, they pour hot liquid metal into the shell. Once it cools, they break the shell away to find the metal art.

This technique is incredibly old. The oldest known examples are about 6,500 years old.

These were gold items found at the Varna Necropolis in Bulgaria. People in the Indus Valley used it around 4,000 BC. A copper amulet was found in present-day Pakistan from that time. In southern Israel, copper objects from the Nahal Mishmar hoard date to about 3,500 BC.

In Mesopotamia, people used this method during the third millennium BC. Sumerian metalworkers were using it around 3,200 BC.

There are many different ways to use this method today. Some artists use it to make glass sculptures. They melt glass chunks inside a heated mould.

Dentists also use it to make gold crowns for teeth. They use a special gold alloy for these restorations. In factories, some makers use a version called lost-foam. They use polystyrene foam instead of wax to make engine blocks. This helps them make shapes that would be too hard otherwise.

You can see how this process connects to many things. It is like making a mold for Jell-O, but with metal. The wax acts as a placeholder for the final shape. Just as a footprint shows where a foot once was, the metal fills the space where the wax used to be.

This process has helped humans make beautiful things for thousands of years. It turns soft, easy shapes into strong, lasting art.

Lost-wax casting is a highly precise manufacturing process used to create metal duplicates of original sculptures. It is also known as investment casting, precision casting, or cire perdue, which is French for "lost wax."

This method allows artists to achieve incredible levels of detail in materials like gold, silver, brass, or bronze. Because the process relies on replacing a temporary material with a permanent one, it can capture very intricate shapes. Today, the term investment casting is often used when the process is applied in modern industrial settings.

The indirect method is a common way to perform this process through several distinct steps. First, an artist creates an original model using wax, clay, or other soft materials. Next, a mould is constructed around this model. This mould usually consists of a soft inner layer made of silicone, latex, or polyurethane rubber. A rigid outer mould, often made of plaster or fiberglass, supports this inner layer.

To ensure the mould fits together perfectly later, makers often use a shim with keys between the parts.

Once the mould is ready, the wax stage begins. Molten wax is poured into the inner mould and swished around to create a hollow coating. This coating is usually about 3 mm thick. After the wax hardens, the hollow copy is removed from the mould. The artist then performs "chasing," which involves using a heated metal tool to smooth out any marks left by the mould.

To prepare for the metal, the artist adds a "spruing" system. This is a tree-like structure of wax cylinders and a top "cup" that provides paths for molten metal to flow in and air to escape.

The next phase involves creating a ceramic shell mould. The sprued wax copy is dipped into a liquid silica slurry and then coated in a sand-like stucco. This process is repeated until a shell at least a half-inch thick covers the entire piece.

The piece is then placed in a kiln for "burnout." The heat hardens the silica and melts the wax, which runs out of the shell. This leaves only the negative space where the wax once lived. The shell is then tested for leaks or cracks before the final pouring.

To pour the metal, the shell is reheated in a kiln to remove moisture and prevent the shell from shattering due to temperature changes. The shell is placed in a sand-filled tub, and molten metal is poured from a crucible into the cup. Once the metal cools, the ceramic shell is hammered or sand-blasted away to reveal the rough casting.

Finally, the artist performs metal-chasing to file down air bubble pits and polish the surface until it matches the original model.

This technique has a very long history spanning thousands of years. The oldest known examples are gold artefacts from the Varna Necropolis in Bulgaria, dating to approximately 4550–4450 BC.

In the Indus Valley, a copper amulet from Mehrgarh dates to circa 4000 BC.

Other significant ancient finds include the Nahal Mishmar hoard in Israel, which contains copper objects from circa 3500 BC.

In Mesopotamia, Sumerian metalworkers were practicing this method by approximately 3200 BC.

Lost-wax casting is used in many specialized fields beyond traditional sculpture. In dentistry, it is used to create gold crowns and inlays, often using an alloy of 60% gold and 28% silver.

Some manufacturers use a "lost-foam" variation to make engine blocks by using polystyrene foam instead of wax. Artists also use the method to create glass sculptures by melting glass chunks into a heated mould. Even textiles have been used in the process, leaving fabric imprints on ancient gold ornaments found in Siberia and Viking Age brooches.