There are some folks who actually make waxed rocks.
However, I am referring to wax used for lost wax casting.
There are many kinds or formulas of wax. There is one group of waxes that has be engineered especially for making master models for use in casting of metals. Casting wax.
In that group there is a wide range of characteristics for color, hardness, formability, strength, machinability, hand carving, injection molding. flexibility, melt point… The list is quite long.
The one thing they all must have is the ability to melt and burn out very cleanly in the burn-out process. While not damaging the internal mold surface.
The lost wax casting process is ancient technology. Know and used for over six thousand years of human history. Certainly not starting with the wax formulas in use today. But there has been a great amount of time to create casting wax with superior characteristics.
Materials other than wax can be used to create the casting models. I have experimented with 3D printing resins with some success.
Anything that will burnout and literally vaporize from the heat of the kiln can be used. I know insects and plant material have been used. It must not leave an ash residue or damage the mold. Clearing actions can be taken in some processes if the mold and sprue is large enough to allow blowing out the debris.
Wax is used in a large scale industrial casting process where a ceramic shell is formed over a (usually hollow) wax master. My process is for much smaller detail casting using a plaster-like investment mold-process used by dentist and jewelry makers.
I think wax really excels (rocks) as casting master material because of several reasons.
First because it burns out so cleanly and investment (the mold material) has been specifically designed to handle the wax.
Second is many forms of the wax are extremely easy to machine and carve with tools. I love both CNC machine carving and hand tool carving. What is shaped in wax is exactly what is produced in the metal casting.
Wax can be sanded and polished for an excellent surface finish before casting. The casting is only as good as the finish on the model
Wax can also be liquid injection molded into rubber molds for making many exact duplicates. More on that in a future post.
The most important feature of wax carving is that it can be additive as well as subtractive. Wax melting points can be engineered. Wax can be built-up as well as carved away. Cool melt wax can be applied to the surface of higher melt wax with a heated tool to add detail or make repairs.
The various creative methods available with totally workable material such as wax makes it the near-perfect material for casting. I love working and creating with casting wax.
All the carving and forming work is lost in the casting process. But as mentioned, there are ways to duplicate a design using rubber molds and wax injection. The wax is always lost, but the design CAN be duplicated if desired.
Sand casting, flexible rubber molds and other processes for casting have their place. They generally preserve the master model. Meaning it is not destroyed in the process. A lot of advantage in not loosing the model.
The prime advantage to lost wax investment casting is the extremely fine detail like filagree that can be captured and presented in the produced casting. Perfect for making jewelry, (teeth), and other super fine detailed parts.
It should be obvious, I love working with casting wax.
It is only one step in a creative process of casting metal. It is the step where, starting with a block of wax, all the shape or form changes from design to tangible model of the intended casting.
Dozens of videos exist on the process. So no details necessary here. Search “lost wax casting”. More info than I can post here.