Bob, Your statement on another thread on the construction of SSTK's.
Gahr used rubber molds, which were made around the master flat bar, that was the ring, when bent to circular form on a mandrel. The rubber molds were made to cast wax copies, which were then hand finished. These wax pieces were then set into an investment material, in a clay or plaster cup, with a sprew added to allow the silver to flow, when the wax was burned out of the hardened investment material.
Now, there are three ways to make the silver ring, in the investment material:
1. by attaching the crucible in a centrafuge which spun as the molten silver was poured into the sprew, thus filling the mold,
2. by placing the crucible into a vacuum chamber which allowed the molten silver to be poured into the investment mold, or
3. by pouring the silver into the investment mold and when filled to the top of the sprew, applying a water saturated piece of leather, with pressure, to the top of the mold, using the steam pressure to force the silver into the mold to take a clear cast.
These are the three processes used in the investment, or lost wax, casting process. In each and every copy made, the resultant silver bar will take the impression of the wax model. Because the wax needs to be hand detailed, after it was taken out of the rubber mold, there can, and will be, slight differences in each piece. Then, when the wax is burned out of the investment material, the silver must flow perfectly, filling every detail of the investment cavity. If the silver captured an air bubble, or did not fully fill some crevice, hand work is needed to clean up the silver bar, that will become the ring, once formed around a mandrell.
Lost wax is not alchemy or involving the black arts, but has been used since the Egyptians made jewelry. It is the method that is currently used to make most jewelry, today. it is the same system that dental workers use to make a replacement crown, of gold, silver or any of the porcelins.
You must allow for differences due to two stages of handwork, on the wax model and on the silver copy of the wax model.
Bob Hritz
Gahr used rubber molds, which were made around the master flat bar, that was the ring, when bent to circular form on a mandrel. The rubber molds were made to cast wax copies, which were then hand finished. These wax pieces were then set into an investment material, in a clay or plaster cup, with a sprew added to allow the silver to flow, when the wax was burned out of the hardened investment material.
Now, there are three ways to make the silver ring, in the investment material:
1. by attaching the crucible in a centrafuge which spun as the molten silver was poured into the sprew, thus filling the mold,
2. by placing the crucible into a vacuum chamber which allowed the molten silver to be poured into the investment mold, or
3. by pouring the silver into the investment mold and when filled to the top of the sprew, applying a water saturated piece of leather, with pressure, to the top of the mold, using the steam pressure to force the silver into the mold to take a clear cast.
These are the three processes used in the investment, or lost wax, casting process. In each and every copy made, the resultant silver bar will take the impression of the wax model. Because the wax needs to be hand detailed, after it was taken out of the rubber mold, there can, and will be, slight differences in each piece. Then, when the wax is burned out of the investment material, the silver must flow perfectly, filling every detail of the investment cavity. If the silver captured an air bubble, or did not fully fill some crevice, hand work is needed to clean up the silver bar, that will become the ring, once formed around a mandrell.
Lost wax is not alchemy or involving the black arts, but has been used since the Egyptians made jewelry. It is the method that is currently used to make most jewelry, today. it is the same system that dental workers use to make a replacement crown, of gold, silver or any of the porcelins.
You must allow for differences due to two stages of handwork, on the wax model and on the silver copy of the wax model.
Bob Hritz
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