Alice Alper-Rein        JEWELRY BY Y2A, Ltd.
Fine Contemporary Art Jewelry in Silver and Gold
            

PMC TIPS, TRICKS AND TECHNIQUES FOR: 
GEMSTONES AND METAL CLAY   
By: Alice Alper-Rein

1.  Cubic zirconia and lab grown corundum fire successfully into PMC.  Some natural stones that have been tested and can be fired directly into PMC at various temperatures are hematite, garnet, peridot, some moonstones, topaz, labradorite, obsidian, and spectrolite. For more information, and specific firing times and temperatures, follow these links to see the results of metal clay and gemstone test firings conducted by Kevin Whitmore of Rio Grande :
http://www.pmcguild.com/download/Tech_Data/Firing_Gemstones_Chart.pdf or  http://www.pmcguild.com/download/Tech_Data/GemTests.pdf

2. When unsure if a natural gemstone will fire successfully at PMC temperatures, the rule of thumb is to fire the stone alone, covered by fiber blanket, so if it explodes, it will be contained and will not be imbedded in the kiln walls. Since there is a chance that the stone will be ruined, during testing, do this only with gems you can afford to lose. If the gemstone survives the firing, there is a good chance it will also survive when fired imbedded in metal clay. Expensive gemstones, gemstones with inclusions or gemstones with sentimental value can be set AFTER the project has been kiln fired. See Tips # 8, 9, 10, 24 below

3. In his book, Natural Gemstones in Metal Clay. A Bench Resource Manual originally released as Clay Gems, Deric Metzger has published the results of his gemstone and metal clay firing tests. The book also contains facts about each gemstone, like Mohs Scale of Mineral Hardness Ratings and trade names.

4. Did you know that Mohs Scale of Mineral Hardness is not a reliable gemstone firing guide. The hardness of a material is measured by finding the hardest material that the given material can scratch, and/or the softest material that can scratch the given material. This scale is most useful for gem setting purposes.

5. Lorrene Baum-Davis has written a self published booklet, Setting Gemstones into Metal Clay.
The booklet covers many different setting techniques including coil settings, syringe settings, extruded settings, using bezel wire, extruded and tube settings, lump clay settings and channel settings, prong settings and more. www.lorrenedavisdesigns.com

6. Set dichroic glass cabochons in low fire metal clay. The lower firing temperature needed to fully sinter the metal clay will not re-expose the glass to its fusing temperature. Since the glass will not fuse to the metal clay, be sure to capture it in a bezel or prong setting using the low fire metal clay or PMC3 syringe from both the front and back of the cabochon. Fire to 1110F at a rate of 1500F per hour, hold for 45 minutes, crash cool to 850F and anneal until it reaches room temperature.

7. A chemical reaction between the silver in metal clay and minerals in some clear fusing glass will cause glass cabochons to develop a yellow halo where they come in contact with metal clay during firing. Glass cabochons that have been capped using Bullseye Crystal Clear 1401 glass won’t have this reaction when fired with metal clay.

8. Here’s one way to include a non-firable gemstone in a metal clay project. Start with bezel wire that is a bit higher than the gemstone. Wrap the bezel wire around the stone. When it fits the stone properly, with just a little bit of wiggle room, use a butane torch and a bit of low fire metal clay (PMC 3 or ACS650) paste to close the bezel wire. Prepare the MC base piece as usual using a minimum 5-6 card thickness. Push the bezel wire just slightly into the MC and secure it in place with thick slip. Cut a small hole in the clay inside the bezel wire frame (in back of where the stone will be set) to help control shrinkage and warping. Dry and fire. When cool, set your stone in place using a bezel pusher or bezel rocker to push the fine silver setting up and around the stone.

9. Here is a fire twice tip for including natural, irregular stones that cannot be fired in your PMC creations. Wrap the bezel wire around your stone as if you were going to solder it in place using traditional methods. When it fits the stone properly, use a butane torch and a bit of PMC 3 paste to close the bezel wire. Prepare your piece as usual using a 4 card thickness (more cards if you plan a deep texture) Audition the bezel setting in place, but don’t join it to the piece. Make a mental note of the 12% shrinkage that will occur after firing and make sure you will have enough space for your bezel. Set aside the bezel. Dry and fire the PMC backing piece without the bezel setting. When the piece is cool, use thick PMC3 paste or a PMC3 syringe to join your bezel to the already fired work. Dry and fire again. When cool, set your stone in place using a bezel pusher or bezel rocker to push the fine silver setting up and around the stone.

10. Here’s a trick for setting some gemstones, pearls and some other items that cannot withstand the heat of a kiln or torch firing. Use an EAR POST COMPONENT. Coat the post (or the pad if you’ll be setting a half drilled stone or pearl) with thick PMC3 slip and insert it into PMC3 clay. The post can be cut or bent to fit the depth of your project.  As the clay fires, it will shrink tightly around the post and grab the grooves or notches on the ear post, securing it in place. Ear posts are available with pads, without pads, with cups and pegs, with prong mountings, snap-set mountings, with loops for dangles, cabochon mountings, with half-balls, balls and with other decorative elements. Pickling may be necessary to remove any firescale that forms on the sterling silver during firing. Set your stones using traditional setting techniques, AFTER firing and burnishing the PMC.

11. Include ceramic shards and beads within your PMC creations by capturing them as you would dichroic glass or gemstones.

12. Use the hollow core adapter to extrude some tubes and let them dry. Cut them up as needed with a single edge razor blade or jeweler’s saw to use as gemstone settings. Create a seat for a fire-in-place gemstone using the proper size setting bur. The stone should sit beneath the clay wall. Moisten the clay tube before dropping the gemstone in. Use slip to add the set gemstone to your project. As the tube fires, it will shrink around the stone, creating a tight bezel setting.

13. Make a clean, tight fitting bezel around CZ’s and lab grown gemstones using PMC+ paper. Here's how: Cut a strip of PMC+ paper to a length 2mm-3mm larger than the circumference of your stone. Wrap the strip loosely around the stone and secure the paper to itself using a glue stick.  Kiln fire, with the flat side of the stone resting against the kiln shelf.  As the kiln fires, the paper will shrink, hugging the girdle of the stone tightly, making a perfect bezel setting. Add the bezel-set gemstone to your PMC project using PMC slip (paste.) Remember to cut a hole where it is placed to allow light to shine through the stone (optional)

14. To insure that you’ll be able to remove a cabochon when trying out how it fits in a bezel setting, slip a length of dental floss under a cabochon before placing it in the bezel. When ready to remove the gemstone, grab the ends of the floss and lift upward, releasing the stone.

15. Here’s a new use for a product that you might be familiar with if you have teenagers. Fun Tack and Tac ‘N Stik are two brand names for reusable adhesive putty used to temporarily hang posters and lightweight objects. If you are firing bezel cups or bezel wire into PMC, so that natural stones (that can’t be fired into PMC) can be set in place after firing, use some Fun Tack to hold onto those stones as you set them in place. If you need to remove a tight fitting stone (before the bezel wire is smoothed permanently over it), nudge it out of its setting with the Fun Tack. Once the bezel wire is smoothed over the stone, test the fit by tugging on the stone with the Fun Tack.

16. Here’s a simple yet very helpful trick to use when trying to shape fine silver bezel wire around a non-firable cabochon in preparation for including the bezel wire in the PMC piece you are creating.  Secure the cabochon to the tabletop with a small piece of double stick tape. With the cabochon adhered to the tabletop, it won’t shift as you work making it much easier to fit the bezel wire around the stone.

17. Designate a special place on your metal clay table to safely store the gemstone, bezel cup, pearl, previously cut out PMC components, jump-rings or any other small items you will be incorporating into your current PMC creation. A small candy dish, ashtray or dessert size paper plate works well for this.  There is nothing more frustrating than going through the exercise of fabricating a special bezel for a unique gemstone, for example, only to be unable to locate the stone when it’s time to set it into place. You’ll always know where to find those small components when you routinely set them down in a particular place on your workbench

18.  Make your own gemstones USING EPOXY RESIN TO ADD COLOR TO PMC
Add a burst of vibrant color to your PMC Creations using 2 part epoxy resins. Epoxy resins are high strength adhesives that are resistant to most chemicals. Also referred to a "cold enameling"
this process is completed last, AFTER your PMC piece has been fired, burnished and polished. Epoxy resins can be found at the local hardware store or through jewelry supply companies. There are many brands, but the one I like best is Devcon-5 Minute Epoxy. Working on a throw-away palette, like a paper plate, measure out equal amounts of resin and hardener, but keep them separate. Using a toothpick, add a very small amount of a coloring agent to one of the parts, and mix thoroughly. Too much coloring agent can prevent the epoxy from setting up properly, so it is best to experiment before working on your final project. Some coloring agents I prefer are Pearl Ex mica powders, graphite powder, speedball acrylic inks, and acrylic paints. When you are satisfied with the color, mix the resin and hardener together. Use a clean toothpick to add the colored epoxy to depressed areas on your PMC creation. Allow the epoxy to cure. Please use caution with epoxy resins. They can be eye and skin irritants

19. Here’s a stone setting trick when using an RTV (room temperature vulcanizing) molding material. Create your mold from the object of your choice (antique button, shell, seahorse, or other found object) and let it set up. When it’s cured, remove the object from the mold. Select the stone you’d like to include and place it into the mold, resting the flat, table side (top of stone) against the mold in the place you would like the stone to sit. Add your PMC to the mold with the stone still in place. When you release the PMC from the mold, the stone will be perfectly set.

20. Did you know that you can pre-fire parts of your design when building a PMC piece? Why would you want to pre-fire? For added strength and to insure that a fragile part won’t break off as you complete the details on a larger structure. Also, sometimes it’s easier to refine or polish a part when it’s not attached to the whole project. For example, a tiny PMC+ paper cut-out shape might be too flimsy to work with or might break down if too much water is applied to it. A thin “branch like” protrusion with lots of detail might be easier to work on if created separately and then attached to the main “trunk” A gemstone can be pre-set in a chunk of clay. How do you pre-fire? Any method from using a butane torch to kiln firing will work. How long do you need to pre-fire for? That depends on the project at hand. You can simply burn off the binder or fully sinter the fragile part. Wait until they have air-cooled and use thick PMC3 slip and lump clay to attach pre-fired parts to your main structure. Fire the finished work for as long and as hot as your inclusions will allow.

21. Here’s a trick to use to flush set a commercially made fine silver bezel cup. Cut the hole for the cup to sit in using the next larger size bezel cup. Secure the bezel cup to the project with thick slip. The clay will “set” the bezel cup in place as it shrinks during firing.

22.  Don’t have gem setting burs? Use a sharpened pencil point to prepare a hole in MC in which to set a faceted gemstone.  Push the pencil point into the clay so that when the gemstone is placed in the hole, the pointy culet sits level in the tapered area created by the pencil point and the girdle of the stone sits below the surface of the clay. As the kiln fires, the MC will grab the stone and lock it in place.

23. Set a heart shaped CZ or other uniquely shaped CZ in a blob of syringe clay. The creamy consistency of the syringe clay will easily conform to and capture the unique shape of these gems.
  
24.  Create a fire-in-place substitute for any size cabochon that won’t survive a kiln firing. Turn the cabochon upside down (curved part down) and wrap 2-3 sheets of plastic wrap tightly around the cabochon. Gather the excess wrap to create a handle and secure it with tape. Push the wrapped cabochon into a lump of non-hardening clay until it’s back sits flush in the lump of non-hardening clay.   Remove the cab and use a tiny spatula to straighten the walls of the impression. Mix up some investment following the manufacturer’s directions for amounts of investment and water. Take the proper precautions not to breathe in the small dust particles. Pour the investment into the impression in the non-hardening clay and let it set up. When set, include this placeholder in your MC project, creating a MC setting or prongs around it. After firing, when cool, the investment will dissolve in water (discard in garbage not down the drain) Slide the “real” cabochon in place. Gently bend any prongs tightly around the cab to set it in place.

25. SETTING GEMSTONES IN MC AT A GLANCE