Gemstones and PMC Silver Clay

Gems and other unique stones can be a beautiful addition to make a truly one of a kind silver clay project. They can become the focal point of a design, or simply add an interesting accent to an otherwise simple design.
Some of our favorite ideas for creating with stones are:
  • Collect rocks while on a vacation to make keepsakes
  • Let children collect stones to make special gifts
  • Collect stones that are unique to your locale to make regionally inspired pieces
  • Use gemstones to make personalized birthstone jewelry
When working with stones it is important to know what the likely results will be. To help determine if a stone is suitable to be fired with PMC+, or PMC3 we will want to clearly define what the stone is made of.

Lets begin by asking if it is "real" or "fake." Naturally occurring stones all have their own properties, some are suitable to fire with a project, others are not.

Artificial stones can be called many things, some common terms are man-made, lab grown, lab created, or simulated. Below are some explanations that may make it easier to identify the properties of a stone.
Laboratory Grown Gems (aka synthetic stones, lab grown, or lab created) are man made stones that are of the same (or extremely similar) chemical composition as their natural counter parts. Most are perfect without any flaws or inclusions. Because these stones are created in a high temperature process they are good candidates for use in silver clay projects, as they will not melt or lose their faceted surface.
Simulated is a term used to reference any man made stone. Stones listed with only this description could be laboratory grown gems, or an imitation of a gem made of other chemicals that may include glass or plastic. Because of the wide range of materials that could be used to create these stones it is important to ask for further information to determine if they will withstand firing and whether they will retain their facets or melt and "round over."
Doublets are stones that are made up of two layers. The base has the coloration, and the top layer is clear. During firing the surface may "round over," losing the faceted shape. In some instances this can be appropriate to the project, but often is not the desired appearance.
Cubic Zirconium (CZ) are available clear to imitate diamonds, and to the naked eye are virtually indistinguishable to most people. CZ stones are also available in a wide variety of colors to mimic other gemstones. CZ stones generally hold up to firing well, retaining their faceted surface. CZ Gemstones
Natural Stones can be beautiful additions to silver projects, however they are slightly more unpredictable. Before incorporating a stone it is important to become familiar with some of the stones characteristics to determine if it will survive a firing as part of a PMC design.
If you are familiar with what type of stone you have you may be able to make some educated estimation about what the results of firing would be. One factor is the "hardness" of the stone (this information can sometimes be found online or in stone reference books). Stones are rated for hardness using the MOHS Scale. This scale numbers from 1-the softest (includes talc and graphite) to 10-the hardest (diamonds). Some stones that are rated above 7 on the MOHS Scale may be fired as part of a silver project. This generally includes quartz, granite and the corundum family, although they may sometimes color shift during firing. Any stones under 7 on the MOHS Scale generally will fracture or even turn to powder during the firing process. Note: Several artisans have reported that diamonds will not withstand firing in this setting due to their carbon based composition.
If you wish to test a stone place it on your kiln shelf, cover it with a piece of fiber blanket, and fire it to 1650 degrees F. It is best to ramp up the temperature slowly, then allow the kiln to cool by turning it off and letting it set. If the stone doesn't crack, explode or turn to dust during this test firing you can incorporate it into a design. Due to the obvious risk that the stone may not survive, or at least may not be recognizable after firing, it is suggested not to test stones that are of great value (sentimental or otherwise). These stones are best reserved for setting after firing by incorporating a bezel setting into the design.


For More Detailed Instruction and Creative Projects See:
Introduction to Precious Metal Clay #6289
This do-it-yourself guide by Mary Ann Devos provides all the information you need to get started and advance to a "master class" level. This easy-to-follow guide explains the clay and tools you will need, as well as showing step-by-step projects with detailed instructions and photos.
precious metal clay Metal Clay: The Complete Guide #6767
Popular author Jackie Truty teaches you how to use this versatile material for gorgeous results. 225 pages of full-color photography. Handy small size of book allows you to easily refer to it right on your worktable as you create metal clay projects.
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Friday, January 25, 2019
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