Monday, July 4, 2011
The method of creating a ball-jointed doll used by Martha Armstrong-Hand is fascinating and wonderful. She started with drawings. Then she made a wire armature and modeling stand to support the armature. She modeled the original sculpt in oil-clay.
Oil-clay is soft and responds instantly to the touch of the sculptor. It is quite easy to build-up forms rapidly. Also, it is quite easy to subtract from the form, to get it exactly right. It is, however, too soft to be polished to a high finish. Due to this limitation, she used an intermediate material to refine and finish her dolls.
The intermediate material requires an extra mold making step. She removed the oil-clay original from the modeling stand and cut it apart. Then she made plaster rough shell molds of the doll parts. The plaster rough shell mold was saturated in water, and molten carving wax was cast into the molds.
Carving wax is an amazing material. It can be added to, subtracted from, and is tough enough to withstand elastic tensioning, for testing the joints of the ball-jointed doll. The carving wax is hard enough to refine to a high finish, suitable for using as patterns to make the final plaster slip casting molds.
Previously I had a question about how far along Martha Armstrong-Hand would take an oil-clay original sculpt before she made the plaster rough shell molds to pour carving wax into. As I am working with my own brown wax original sculpt, Aalish, and with my Carving Wax Test Doll, I am discovering what that point should be.
Like oil-clay, brown wax is relatively soft, and easy to model. It is, however, firmer than #2 oil-clay. Still, it is too soft to refine to a high finish, suitable for use as a pattern for making the final plaster slip casting molds. So even though I am using the brown wax to create the original sculpt, I will still need to make carving wax parts for my BJD.
It is much easier to build-up forms using oil-clay or brown wax, than it is to try and build-up the same forms in carving wax.
It is much easier to refine the cast carving wax forms, than it is to build-up carving wax.
I am discovering how far I need to take my original sculpt before I make my molds for casting carving wax. It is possible to make the first set of molds for casting carving wax from plaster, hot-pour moulage, or silicone rubber. Of those three mold materials, I think that hot-pour moulage is the best option because it is reusable, and it has a relatively inexpensive initial purchase cost.
Silicone rubber can also be used for making molds for casting carving wax. This type of mold, called a waste mold in the book, Pop Sculpture uses a combination of old chopped-up silicone rubber molds, and some fresh silicone rubber. The molds are cured under pressure in a pressure pot. The downside to this method is that new silicone rubber must be used until you have made enough dolls to have old molds to chop-up. Also, it requires the use of a pressure pot, and air compressor.
Plaster is relatively inexpensive, compared to silicone rubber, and to the initial cost of hot-pour moulage. However, plaster is not reusable. Over the years, I have seen a 100 pound bag of Moulding Plaster go from $11USD, to $22USD, to $40USD. With the cost of petroleum products getting more and more expensive, I do not think plaster will ever get any cheaper, and is more than likely to continue to increase in cost.
So my contribution to Martha's Method of making a BJD is to use hot-pour moulage to make the intermediate molds to make the molds for casting carving wax. The hot-pour moulage works very much the same as a water-saturated plaster mold, or a silicone rubber mold, for casting carving wax. But due to it being reusable, and not requiring expensive studio equipment, it becomes a very inexpensive intermediate mold making material.
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