Gemstones, ceramics and glass

[Todd]

These Q&A's courtesy of Art Clay World FAQ pages [with a couple of adds & edits]
Gemstones
Q. What gemstones are best to use in Silver Art Clay?
We recommend and sell laboratory grown stones, and cubic zirconium (CZs). You can easily set these into the Art Clay and fire them with a kiln, torch, or gas stove. Remember to let pieces with stones air cool, quenching a hot stone may crack or shatter the stone.
Q. Can I use natural gemstones?
Some natural stones may be used, but there is always the possibility they will break, or shift colors. Stones with a hardness greater than 7.5 on the Mohs hardness scale should be strong enough to survive firing. However, inclusions in the stone can cause the stone to break, and the heat may also cause the stone to shift colors, often in unattractive ways. For more specific details regarding a particular stone, ask in the forum.
Q. What gemstones should I avoid using with Art Clay Silver?
Diamonds should not be fired, as well as most members of the quartz family. Doublets are not recommended because the clear top layer, on this type of stone, may melt. the glues may burn out as well. Many green stones will not hold their color as well as often being doublets.

Set Natural Stones
Q. How can I set natural stones in Art Clay that can't be fired?
You can set natural stones and other materials too delicate to survive the firing process by creating a bezel using fine silver bezel wire, much like regular bezel settings. Measure and form the bezel wire, as you would traditionally. Seal the seam using Oil Paste, and fire. Then press it into the Art Clay. Use Art Clay paste or syringe at the joint to reinforce the work and compensate for shrinkage. Fire the Art Clay with the bezel. Sometimes you may need to fill/repair some shrinkage cracks and do a 2nd firing. After you polish the piece, you can place the stone into the bezel and close using traditional methods.

Firing with Ceramics
Q. Can you fire Silver Art Clay onto ceramics?
Yes, you have several options for working with ceramics. You can work with glazes that "open" at the temperatures Art Clay is sintered at, or you can apply Art Clay to bisque. You can also use Overlay Paste which is specially formulated to bond to glazed surfaces like porcelain.

Firing with Glass
Q. Can you use glass with Art Clay Silver?
Low Fire 650 Art Clay works great with glass. At lower temperatures of 1275-1300°F there is little glass movement, and no yellowing. The glass will stick directly to the silver, allowing for very creative designs. Care should be taken to properly handle and fire the glass, as glass should be annealed slowly in a kiln. Fiber paper should be used under the glass to give it a smooth backside. If you wish to draw or paint a silver design on a glass surface, Overlay Silver Paste can be used for that purpose, as it can be fired from 1200°F, and is formulated to adhere to smooth surfaces.