Making & using plaster gems with PMC

Although CZ and many other gemstones can be successfully fired into PMC, I often find that the brilliance (at least of CZ) is slightly diminished by this process. So I made a flexible rubber mould of some 5.5x5.5mm CZ hearts, then cast the pavilions using a fairly hard casting plaster. Each tended to have a small missing piece at the point of the pavilion due to an air bubble, but this proved not to be a problem. When well dry, they were embedded at girdle height in plastic PMC shapes (themselves embedded in flexible rubber moulds), the whole de-moulded, dried and fired at 800C. This higher temperature possibly helped to denature the plaster sufficiently that it was easy to clean out from the cured (i.e. sintered) PMC. It would only remain then to set the coloured CZ hearts using a spot of glue. However that is not what I actually did - on a whim, I melted dichroic glass fragments into the heart-shaped cavities in some samples of the uncured PMC, whilst also firing some 15mm PMC heart shapes with 5.5mm heart-shaped coloured CZ embedded in the uncured (unsintered) silver. In the side-bar to the right, you will see examples of the fired-in-place CZ (right-most two hearts, amethyst and orange respectively) along with the left-most three specimens which had variously coloured dichroic glass pressed in them while red-hot and fluid.

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