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Lost Wax Bronze Casting
The bold parts create a shorter version.
1. I create the form, usually in clay. Sometimes I have a definite idea in mind or sometimes I have no solid plan. Instead I see what the clay begins to look like as I move it around. I believe creativity has to do with recognizing the possibilities in front of the artist and the accidents that can become something really magnificent. I refine this form, specifically paying attention to the lines that are formed when various curves intersect to create a pleasing definition. This is used to create the mold.
2 Next I evaluate the form or sculpture to determine how the mold is to be made. I prefer to make a hard plaster-sectioned mold if the piece contains few undercuts. This involves first building a wood frame around the sculpture. I find the point at which the pieces of the mold could easily be separated. This allows me to make 2 separate mold sections. The plaster is then poured over that part of the sculpture. This creates one part of the mold. The other part(s) is done similarly.If the piece is very detailed with numerous undercuts, a rubber or latex mold is required. I do this by painting on numerous layers of a liquid rubber product until the thickness is about 1/2 inch. After this, I make a hard plaster "mother" mold to encase the softer mold so it doesn't stretch out of shape when filled with a liquid.At this point I hope to avoid dramatic moments such as a mold container breaking and plaster leaking everywhere. Another dramatic moment could occur if I fail to select the right place to create the separation and the mold won't separate without breaking the sculpture.
3. Once it is complete and cured I fill the mold with a special wax that has been heated to a liquid state. Depending on the size and shape of the sculpture, it may be left to cool to a solid, or after a few minutes of built-up thickness, the remaining liquid is poured out leaving a hollow form.
4. After the liquid wax cools and becomes solid, I remove it from the mold and clean it. This involves eliminating any mold lines or air bubbles, making desired textural changes, or adding small details. This is why in lost wax bronze casting, the pieces still have a very individual presence. Sometimes I have even repositioned a head or arm to create a different feeling.
5. The refined wax sculpture is now ready to be set up for the casting of the bronze. I determine a plan for the gating. This is a series of wax tubes of various sizes that are added to the sculpture. These allow the liquid bronze to be poured into the sculpture and allow air/gasses to escape. Although there are many ways to do this, the set up must be correct so the sculpture is filled completely. Also, if the sculpture is hollow, a separate step involves working out this facet of the pour.
6. Once the gating is complete, the sculpture is then "invested". I make a cylinder out of expanded metal and place it around the sculpture. Then I surround this with tar /roofing paper and secure it with several strands of wire. Next I fill the cylinder with a mixture of sand, plaster and water, leaving the mouth of the gating visible for the pour.
7. The wax sculpture and gating must then be melted out so the bronze can take its place. I do this by heating the investment in a kiln for 36 to 48 hours at 1000 degrees F.
8 Finally I am ready to pour in the liquid bronze. The bronze is heated to 1950 to 2121 degrees, and poured into the investment. The bronze must be at the correct temperature and poured correctly to fill the hollow area in the investment. If the bronze cools too quickly, it can be an incomplete pour. If it is too hot, it can break the mold. If it is poured too fast, air bubbles may form that make an unattractive surface. Heavy protective clothing is worn because the heat from the crucible is very high and there is always the threat of a spill.
9. The excitement comes when I break the investment away from the actual bronze sculpture. I hammer and chisel to remove it…but carefully. I then cut off the to reveal the initially created form.
10. But the most careful work is still to come - chasing. I chisel, remove the gating. weld, grind, sandblast, sand, polish, make and attach a base, and add a final patina.
11. Admire and enjoy
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