Firing Precious Metal Clay with gemstones

Natural things like pearls and coral cannot be fired under any circumstances - kiln or torch - as they will burn on contact with the flame. Semi precious stones like turquoise and amethyst are made from layers or crystals and will pull apart under heat.

To set stones like this we recommend taking a cast of them in plasticine, mixing up some plaster of paris and pouring it into the mould. Allow to harden completely and then set the plaster into the PMC and fire as normal. Once fired and cooled, chip out the plaster and glue the stone into place with some sturdy glue - like a two part epoxy glue.

You can certainly torch fire cubic zirconias into PMC - these are lab grown natural gemstones that withstand heat. But be warned, very occasionally they change colour when fired.

As for glass, you can only torch fire dichroic glass - it's manufactured to withstand really high temperatures. Set it into the PMC and ensure that the PMC setting is really secure, if it's not it will come apart as the silver shrinks and glass expands. When you torch fire, concentrate the flame on the PMC, and only fire the edges of the glass that meet the PMC. Allow to cool down naturally, otherwise the glass will crack.

All other types of glass need to be kiln fired.

Firing PMC with gemstones. Temperature guide (External link)