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woman's hands with seafoam green nail color is holding a piece of red wax that she is carving

Lost Wax Casting

Lost wax casting, also known as wax casting and investment casting, is a jewelry-making technique that dates back about six thousand years. Earliest makers used beeswax to make the wax models, but now we have wax specifically made for jewelers to use. A breakdown of the history, process and materials used in wax casting could take up a book. Here, you’ll get the basics.

The Lost Wax Casting Process

  • Step 1: The process starts with a design that might be sketched out or created using computer-aided design (CAD) software. Another method is for the maker to use the wax and see where the process takes her. Whatever the creative process, the jeweler sculpts the design in wax or, if CAD is used, a 3D printer makes the design in wax or resin. 

  • Step 2: A piece of wax (sprue) is attached to the wax model and that sprue is attached to a central wax stem, forming what is known as a "wax tree" or "sprue tree." This allows multiple pieces to be cast simultaneously. This step is an artform all its own. Doing this requires attention to detail and a solid understanding of where and how the molten metal will flow.

  • Step 3: The wax tree is then placed in a metal cylinder called a flask.

  • Step 4: The flask, with the wax tree secured inside, is filled with a plaster-like material called investment. This material hardens (sets) to form a mold around the wax models.

  • Step 5: Once the investment is set, the entire cylinder is heated in a kiln (think super-hot oven). This is step is called “burn out” because the wax melts and flows out, hence the name “lost wax”, leaving behind a hollow mold.

  • Step 6: Molten metal, such as silver, gold, or bronze, is poured into the hollow mold. Another method for getting the molten metal into the flask is with a centrifuge that “shoots” the molten metal into the flask. The metal fills the cavity left by the melted wax, taking on the shape of the original design. 

  • Step 7: After the metal has cooled and solidified, the investment mold is broken away to reveal the metal casting.

  • Step 8: The individual pieces are cut from the central stem, and any remaining investment material is cleaned off.

  • Step 9: The piece looks very rough at this stage. It still needs to be refined and polished. This is also when you would add details (stone setting, engraving, or adding patinas).

Making a mold:

Whether you spell it mold or mould, you will mold your finished piece if you want to make copies of it. There are a couple of ways to do this, but in simplest terms, the piece is set into silicone until it hardens around the piece. The mold is then cut in half, the piece removed, and a wax injector is used to inject the mold, each injection results in a duplicate (in wax form) of the piece that you cast. Repeat the injection step as many times as you want. All those wax duplicates are sprued onto the “tree” described above, put into a flask and cast. The result is a metal “tree” of identical pieces of jewelry.

Lost wax casting is an interesting and ancient technique that remains a standard in modern jewelry making. It allows for intricate designs, can be used with a variety of metals and can be consistently reproduced more quickly than by fabrication.

I love fabrication (sewing, soldering, hammering metal), but have made a couple of classic KBeau pieces using a mold and casting process. Explore my lost wax cast jewelry (the coffin key and the rattlesnake rattle) and learn the story behind these pieces.