I do a lot of wax carving with my students because it is such a versatile skill.
I often get the questions, "What is lost wax casting?" and "Why are we carving wax when I want to make metal jewelry?"
Casting is a commercialized process, and there are companies referred to as casting companies who can cast your pieces for you. If you are interested in learning more, please feel free to reach out to us and see how we can help!
USEFUL TERMS
Sprue - A sprue is an additional wire added to a piece to prepare it for casting or molding.
Casting Tree - A casting tree is when multiple individual pieces of similar size are attached to a thicker center sprue to create a casting tree.
Flask - A flask is a metal cylinder, mainly steel, set around the piece to prepare it for casting.
Investment - Investment is a powder that becomes like cake batter when mixed. This mixture is poured into a flask set on a casting base. The casting tree is held in the middle by the casting base. After the investment is poured, the air bubbles are removed, and the flask is left until the investment hardens.
Casting Base - A casting base is normally made of rubber or clay as shown in the images below. It is a circle with a raised edge in which the flask fits tightly inside. The center has a half-round mound shape with a hole in the center for the casting tree to be held.
Molten - Molten is when metal is heated until it is in a liquid form.
THE STEPS
1. Adding a Sprue
When a piece is sent for casting, a sprue will be added for the function of productivity when casting in volume. As you can see in the next image, the sprue is used to attach the piece easily to a larger casting tree.
2. Make a Casting Tree
This is a large casting tree, similar to what you would see in a casting company. It is possible to make a smaller tree if casting on a personal scale, but is quite a bit of work to do piece by piece. Studio Dahl occasionally offers casting demonstrations in the studio.
3. Weighing the Waxes
This part in the process is very important and is a formula I teach in class. Using specific gravity calculations, the waxes must be weighed and converted to the weight of the desired metal. This is to ensure the flask will completely fill out when the metal is cast.
4. Setting the Flask with Investment
This process includes a number of steps including: preparing the tree for investment, mixing the proper investment ratios, degassing the investment, and finally setting the flask to harden over the waxes.
5. Burning Out the Wax
Once the investment has hardened over the waxes and dried for a period, the flask gets placed into in a kiln, as shown in the image to the right, and heated to casting temperature. During this process, the wax is burned out and a negative space is left in the flask to be filled with metal.
6. Melting Prepared Metal Ratio
The perfect ratio of metal to fill out the flask, weighed out during step three, is melted down to be cast.
7. Casting in Desired Metal
Once the flask is up to casting temperature and the metal is molten, casting occurs, using pressure to force the metal into the empty wax chamber. Professional casting companies use precise vacuum pressure regulated by industrial casting machines.
8. Quenching the Flask to Expose Metal
Once the casting process is complete and the metal has been cast, the flask is directly quenched in water, where the investment dissolves and exposes the metal casting tree or piece.
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