The art of jewelry making has evolved significantly with the advent of metal clay, a medium that allows artisans to sculpt with the malleability of clay and the durability of pure metal. However, a critical challenge arises when working with delicate gemstones. While some stones can withstand the extreme temperatures required to sinter metal clay, the vast majority of natural gemstones, pearls, and organic materials cannot. When a stone is fired in the kiln alongside the clay, the heat can cause fracturing, discoloration, or total destruction of the material. Consequently, the most reliable method for incorporating high-value, heat-sensitive, or organic stones into metal clay jewelry is through post-firing setting techniques. This approach ensures the integrity of the gemstone is preserved while leveraging the unique properties of metal clay to create bespoke, custom settings.
The decision to set stones after firing is not merely a safety precaution; it is a strategic choice that expands the palette of available materials. By separating the firing process from the stone setting, artists gain access to a much wider range of gemstones, including freeform natural stones, pearls, and delicate glass pieces that would otherwise be lost in the kiln. This methodology requires a shift in workflow, demanding precision in pre-firing construction and post-firing assembly. The following guide explores the specific techniques, tools, and structural considerations necessary to execute these settings with professional quality.
The Thermal Barrier: Why Post-Firing is Essential
The fundamental principle governing stone setting in metal clay is thermal tolerance. Metal clay, particularly fine silver or bronze varieties, requires firing temperatures that can exceed 900 degrees Celsius. This intense heat is necessary to sinter the metal particles into a solid, durable mass. However, natural gemstones, pearls, wood, bone, and certain types of glass are not heat-resistant. Subjecting these materials to the kiln environment results in catastrophic failure. Natural stones may fracture due to thermal shock. Pearls, being organic, would incinerate. Bone and wood would simply burn away.
Therefore, the standard procedure for non-fireable stones is to create a secure setting within the metal clay base, fire the piece to achieve a solid metal structure, and only then insert the stone. This method mirrors traditional jewelry making techniques where stones are set into pre-finished metal, ensuring the stone remains unharmed.
The choice to use post-firing settings is often driven by the artist's intent. If the goal is to sell high-quality, unique jewelry, avoiding heat treatment of the gemstone is the professional standard. This ensures the final product maintains the natural beauty and structural integrity of the stone, which is often the focal point of the design. While "fire-in-place" techniques exist for heat-resistant stones, the risk of damaging expensive or unique natural materials is too high. The post-firing method allows the artist to select the most beautiful natural gemstones without the fear of thermal damage.
Pre-Firing Structural Preparation
Creating a setting that functions correctly after firing requires meticulous preparation before the clay ever enters the kiln. The most common technique for non-fireable stones involves embedding a bezel wire or a prong setting into the fresh clay. This process is distinct from simply placing a stone on a flat surface; it requires building a structural frame that will securely hold the stone once the metal clay has been fired, shrunk, and polished.
The most widely used method is the embedded bezel wire. This technique involves cutting and forming a piece of wire to fit the stone. Precision is paramount here. The bezel wire must be sized to fit approximately 1mm larger than the stone. If the bezel is significantly larger, such as 2mm or more, the resulting gap makes it nearly impossible to set the stone evenly, leading to a loose fit or requiring complex lapidary adjustments. If the bezel is too small, the stone will not fit. The wire is then embedded at least 2mm deep into the fresh metal clay base.
To ensure the wire remains anchored during the firing process, the connection points must be reinforced. This is achieved by applying a thick layer of slip—a liquid metal clay mixture—to the base of the wire where it meets the clay. This slip acts as a weld, fusing the wire to the base. The slip should be applied to both the inside and outside of the base of the bezel wire. Once the piece is dried, the slip connection is refined and smoothed to create a seamless transition between the wire and the base.
Following the firing, patina, and polishing of the metal clay base, the bezel is ready to receive the stone. The stone is inserted into the bezel, and a bezel pusher tool is used to gently bend the wire over the girdle of the stone, securing it in place. This method allows for the inclusion of both cabochon and faceted gemstones.
An alternative to the embedded bezel is the use of pre-made bezel cups or prong settings. Manufacturers offer templates in various shapes and sizes, starting at 6mm, covering rounds, ovals, marquises, diamonds, and trillions. These pre-formed components can be embedded into the clay. However, the custom wire method remains popular for its ability to accommodate freeform stones that do not fit standard templates.
Structural Integrity and Shrinkage Dynamics
One of the most critical technical challenges in metal clay work is managing shrinkage. Metal clay shrinks significantly during the firing process, with shrinkage rates varying by brand and type. This dimensional change creates a complex dynamic when setting stones post-firing.
The primary risk lies in the mismatch between the shrinkage of the clay base and the stability of the embedded wire. If the base shrinks at a different rate than the wire, or if the wire is not securely anchored, the setting can deform. In severe cases, this can cause the metal clay base to develop cracks during the firing process. Furthermore, if the bezel wire is not sized correctly relative to the stone's dimensions after shrinkage, the stone may become loose or fail to fit at all.
To mitigate these risks, the wire must be anchored effectively. A common technique is to bend or notch one end of the wire before setting it in the clay. This physical deformation creates a mechanical anchor that resists movement as the clay shrinks. Additionally, using fine silver wire is recommended, as it has better compatibility with metal clay shrinkage compared to other alloys.
When embedding the bezel, ensuring the wire is deeply embedded (at least 2mm) and reinforced with slip is non-negotiable. The goal is to create a monolithic structure where the wire and the base move as one unit during firing. If the stone is inserted after firing, the setting must be perfectly sized to the stone. This often requires precise measurement and, in some cases, lapidary skills to adjust the stone or the setting if the fit is not snug.
Advanced Techniques: Prongs and Pegs
Beyond the traditional bezel, post-firing settings include custom prongs and peg settings. These methods offer unique aesthetic and functional advantages, particularly for organic materials like pearls or for creating a "freeform" look.
Custom Prong Settings Custom prongs are an excellent way to display freeform natural gemstones. These prongs are often hand-formed from metal clay or wire and embedded into the base. The video tutorials available in the field demonstrate how to create custom prongs that eliminate seams and provide a secure hold. The advantage of custom prongs is their ability to grip irregular shapes that standard bezels cannot accommodate.
Peg Settings for Pearls and Stones A specialized technique involves setting pearls and certain stones on pegs. Unlike beads which are drilled all the way through, pearls and some stones are often drilled only halfway, leaving a solid base for the stone to sit on. - Fine silver wire can be implanted directly into fresh or dry clay. - One end of the wire is bent or notched to act as an anchor against shrinkage. - Slip is applied to the base of the wire to fuse it to the clay. - The stone is pre-fitted on the peg to ensure a snug fit. If there is any play or movement, the wire may bend or snap off over time. - A tiny drop of two-part epoxy is placed on the bottom of the peg before insertion. Excess epoxy is wiped away immediately.
This method is particularly effective for pearls, which are too delicate for heat but require a secure mechanical connection. The use of epoxy provides an additional layer of security for the stone, ensuring it remains fixed even as the metal base is worn.
Tools and Materials for Post-Firing Work
Executing post-firing stone setting requires a specific toolkit distinct from the initial clay preparation. The process demands precision tools to manipulate the metal setting without damaging the stone.
Essential Tools - Bezel Pusher: Used to gently bend the bezel wire over the stone's girdle. This tool allows for even pressure application, preventing the stone from cracking or the wire from deforming. - Syringe: For specific techniques involving glass or syringe set gemstones, a syringe tool is used to apply setting material or to manipulate the setting structure. - Templates: Pre-made templates help in sizing the clay base to fit the stone precisely. Templates are available in various shapes including round, oval, and marquise. - Epoxy: Two-part epoxy is essential for securing stones that are set on pegs or where a mechanical grip is insufficient. - Lapidary Tools: In cases where the stone or setting does not fit perfectly due to shrinkage variances, lapidary skills and tools may be required to adjust the stone or the metal setting.
The choice of metal clay is also crucial. Fine silver metal clay is often the preferred medium for these settings due to its high purity and compatibility with the setting wires. Other types of metal clay may have different shrinkage rates that complicate the setting process.
Quality Control and Risk Management
The post-firing method, while safer for stones, introduces its own set of risks that must be managed to ensure a high-quality result.
The Shrinkage Variance Problem A significant risk is the inconsistency of results based on the varying shrinkage rates of different clays. If the bezel wire is embedded, the difference in shrinkage between the wire and the clay can cause the bezel to deform. This deformation can lead to a setting that is too large or too small for the stone. In extreme cases, this results in the need for lapidary work to resize the stone, which is time-consuming and requires specialized skills.
Structural Failures If the connection between the wire and the clay is not reinforced with slip, the wire may shift during firing. This can lead to cracks in the metal clay base. Furthermore, if the stone is not fitted snugly on a peg setting, the wire is prone to bending and snapping off during normal wear.
The Epoxy Solution To combat the risk of the stone becoming loose, the use of two-part epoxy is recommended, especially for peg settings. A tiny drop of epoxy applied to the base of the peg provides a chemical bond that complements the mechanical fit. This dual security system ensures the stone remains secure even if the metal setting is subjected to stress.
Economic and Time Considerations Experimenting with embedded bezel wires carries a high risk of losing dedicated creative time. If the setting deforms or cracks, the entire piece may be ruined, resulting in a significant loss of labor and material cost, particularly when using expensive fine silver clay. Therefore, while the embedded bezel wire method is viable, it requires careful planning and execution. Some artists prefer using embeddable prong settings, which have minimal negative impact on the firing process when using fine silver, offering a more reliable alternative for complex designs.
Comparative Analysis of Setting Methods
To provide clarity on the available options, the following table outlines the key characteristics, benefits, and risks of the primary post-firing setting methods.
| Setting Method | Best For | Key Requirements | Primary Risk |
|---|---|---|---|
| Embedded Bezel Wire | Cabochon and faceted stones | Precise 1mm sizing, slip reinforcement, deep embedding (2mm+) | Deformation due to shrinkage variance; potential cracking of base |
| Peg Setting (Pearls) | Pearls, half-drilled stones | Snug fit, epoxy application, notched wire anchor | Wire snapping if fit is loose; requires precise drilling |
| Custom Prongs | Freeform natural stones | Hand-formed prongs, custom fitting | High risk of deformation; requires lapidary adjustment |
| Syringe Setting | Glass/dichroic stones | Syringe tool application | Limited to specific stone types |
| Pre-made Bezel Cups | Standard shapes (6mm+) | Template use, slip connection | May not fit freeform stones perfectly |
This comparison highlights that while post-firing offers safety for delicate materials, the structural integrity of the setting is heavily dependent on the precision of the pre-firing construction and the choice of materials.
The Artisan's Workflow: From Clay to Finished Piece
The successful execution of post-firing stone setting follows a logical, step-by-step workflow that integrates the unique properties of metal clay with traditional jewelry making principles.
Phase 1: Design and Preparation The process begins with selecting the stone and determining the setting type. If using an embedded bezel, the artist must cut and form the wire to fit the stone exactly 1mm larger. This precision is critical. The wire is then notched or bent and embedded into the fresh clay base, ensuring a 2mm overlap. Thick slip is applied to the connection points to fuse the components.
Phase 2: Drying and Firing The piece is allowed to dry completely. Once dry, it is fired according to the manufacturer's schedule. This step transforms the clay into solid metal. Crucially, the stone is NOT present during this stage. The firing consolidates the metal structure, including the embedded wire.
Phase 3: Refinement and Stone Insertion After firing, the piece is cleaned, patinated, and polished to a mirror finish. Only then is the stone inserted. For bezel settings, a bezel pusher is used to bend the metal over the stone. For peg settings, a drop of epoxy is applied before inserting the stone. The final result is a piece where the stone is securely held within a fine silver setting, free from thermal damage.
Phase 4: Quality Assurance The final step involves inspecting the fit. If the stone is loose, the artist must evaluate whether the setting needs adjustment. This may involve filing the bezel or the stone itself. The goal is a "snug fit" with no play. Any movement indicates a potential failure point that could lead to stone loss or wire breakage.
Conclusion
Setting gemstones in metal clay through post-firing techniques represents a sophisticated approach to jewelry making that balances the artistic freedom of clay with the durability of fine metal. By avoiding the thermal destruction of delicate stones, artists can incorporate a vast array of natural, organic, and fragile materials into their work. The key to success lies in the meticulous preparation of the setting prior to firing. Whether using embedded bezel wires, custom prongs, or peg settings, the integrity of the final piece depends on precise sizing, effective anchoring with slip, and careful management of shrinkage dynamics.
While risks such as base cracking or setting deformation exist, they can be mitigated through the use of fine silver, proper wire anchoring, and the strategic application of epoxy. This methodology allows for the creation of one-of-a-kind jewelry that showcases natural beauty without compromise. The ability to customize prongs and bezels ensures that even the most irregular, freeform stones can be displayed with professional security. Ultimately, the post-firing method empowers the artisan to create high-quality, durable jewelry that honors the unique characteristics of each gemstone.