Lost wax casting is the technique I use for the majority of my work, including my vine and leaf pieces and Story Rings. It is an ancient technique that has been used in many cultures for centuries. Regardless ifthe resulting product is a ring, pendant, earrings, etc., a design is created out of wax. The wax is eventually cast into metal. The original form is referred to as a wax pattern or wax model. Most jewelry stores purchase commercial wax patterns pre-made, which is how they start the majority of their designs. However, I take pride in designing and making all of my waxes.
The two most common ways of wax working are Soft Wax Build-up and Hard Wax Carving.
Soft wax work is a method few jewelers are skilled in. Though challenging, I prefer this delicate procedure. I have developed my own technique of using soft wax sheet and wires. I work with a very old fashioned method of manipulating the wax, using a dental tool over an alcohol lamp. I am able to control the heat and work in a very precise and intricate manner, which allows me to create very delicate designs. I call this Painting With Wax. This is a very time consuming process, and some waxes take up to a hundred hours.
Hard Wax Carving is very different. This is a good technique to use if you want to carve a band or have a lot of flat surfaces. This wax is very strong and can be drilled, filed, and carved. This material lends it self to very contemporary designs. I often use hard wax for a base to do my soft wax work on, such as for my Story Rings. After I have finished making the model exactly like I want it to look, it is ready to cast.
Casting begins with attaching the wax pattern to a rubber base. This process is called spruing and the base is called a Sprue Base. Depending upon how complicated the item is, this may be all that is necessary. Although, if the wax is large or has a lot of detail, it may require numerous sprue wires that act as channels for the metal to eventually flow through. Following this process, a stainless steel cylinder (flask) is placed around the wax and attached to the sprue base. Then a material called investment is mixed and poured over the model, filling up the entire flask. Investment is plaster like and heat resistant. After investment has hardened, the rubber base is removed and the flask is placed in a kiln.
While in the kiln, the wax burns out and escapes through the hole in the bottom. This hole was created by the wax that was originally attached to the rubber base. There are many variables. Generally, the kiln is heated upto 1200 degrees and burns for approximately 5 hours. After all of the wax has burned out, you are left with an empty cavity where the wax originally was. This is the working mold.
The following process is casting the metal into the flask. There are three main ways of casting: Pressure, Centrifigul and vacuum. I usually use vacuum casting. The viscosity of metal is not like water, which would simply flow into the openings. Metal has to be forced into the flask or it would just sit as a molten blob at the mouth ofyour flask and ruin your casting.
When your flask has been brought up to temperature and all your wax has burned out, it's time to melt your metal. This is done in what's called a crucible and is usually heated with a torch. After your metal is completely melted the hot flask is removed from the kiln and placed on a vacuum machine. The investment is porus enough to allow the suction through and strong enough to keep from being sucked out itself. The flask sits with the sprue opening at the top and the molten metal is poured in.
After sitting for a few minutes, the flask is then dropped into a bucket of water. Here, the hot investment is removed from the now metal item you cast. Hopefully, all the parts and pieces are where you intended them to be. Otherwise, it's back to wax carving all over again. If the casting goes well, you are ready to start sawing off the metal sprues.
Then comes the rest of the finishing work: grinding, filing, polishing, stone setting, or whatever else your finished product entails.