There is so much you can do with platinum and platinum designs can enhance intricate and beautiful gemstones when put together. This article talks about the how and why when working with platinum.
My skills as an artist combined with my years of experience at the bench have given me a practical approach to jewelry. While I want to achieve a bold, sculptural look, my jewelry has an appeal because it is also wearable and enduring. I often design with my artist’s heart, only to be tempered by my technician’s hand that dictates what can be achieved in wax and metal, the media of my art. Conversely, some of my best designs are a product of technical skills meeting the challenge of an artistic hand.
Since coming out on my own as a designer, I have worked to define a distinctive, unique style as presented in my most recent collections. The driving inspiration behind my designs is a desire to unleash the elusive beauty and innate sense of self esteem that emanates from the individual in the wearing of fine jewelry.
Why Work in Platinum?
Platinum is in demand with a growing market in the United States and Europe, and has an already established market in Japan. Platinum is not a fad, historically platinum has been associated with such famous names as Cartier, Fabergé and Tiffany & Co. Platinum was the metal of choice in the United States from the late 1800s until World War II, when its use was restricted for the war effort. White gold was introduced as an alternative white precious metal. Platinum is the world’s rarest, purest, strongest and most precious of jewelry metals. These qualities give platinum a life span longer than the average human life span.
Platinum is ideal for setting stones, a diamond’s cut and color are complemented by platinum’s white luster. Precious gems are held more securely in platinum. Because of its malleability, there is less chance of breakage in a setting made of platinum. The platinum over the stones in a setting won’t wear away as quickly as prongs made of gold.
Platinum is pure both physically and visually. Platinum is combined with only 5% or 10% alloys, making it purer than 14Kt gold (58.5% pure) or 18Kt gold (75% pure). This purity means that platinum is hypo-allergenic, allowing anyone to wear it. Platinum’s purity of color makes it totally non-conflicting with any other metal, stone, or mode of dress.
In combination with gold, platinum takes on a new versatility. It can be worn with any other piece of jewelry. When a designer works in platinum, he is perceived by customers and peers to have earned the title of Master Jeweler.
Possibilities in Design
Brightly polished platinum assumes a very fluid appearance that can greatly assist flowing sculptural shapes or soften harsher shapes. Platinum’s truly mirror surface can be utilized to reflect neighboring stones or surfaces.
Platinum holds its polish, even when heated. This allows the jeweler to pre-polish platinum parts before assembly. Platinum’s very high melting point allows for assembly of very delicate platinum parts against extremely heavy gold forms. A variety of gold inlay possibilities are possible, from gold flake to artistic lines and designs.
Platinum can be drawn or rolled as thin as a thread or sheet of paper. Platinum may also be formed to echo or follow another shape more easily than gold.
Texture can help to create mood in a piece—from subdued to dramatic to chaotic. Texture can emphasize color differences between platinum and gold. A matte finish can be achieved with rubber wheels. A satin or brushed finish can be achieved with emery paper or a wire brush. Other texture possibilities include stone finishing and sand blasting. Gravers, burrs, and chasing tools can be used to create a variety of textures.
Considerations in Design
The density of platinum makes it polish much more slowly than gold. If platinum and gold are flush, some steps must be taken to adjust for this difference in polishing speeds. Satin or matte finishing one or both surfaces is the easiest way to contend with this problem. One can drop one edge, making a ledge so that both metals can be polished separately. Placing a groove between the two metals is yet another way of separating the two polished surfaces.
The heaviness of platinum can add to its perceived value. Although, if you make the piece too large or too heavy, it can become unwearable or uncastable.
Working in Platinum
Platinum castings may be heat treated to assist in hammering, burnishing, or to avoid cracking in general. Set a kiln at 700oC or 1300oF. Pickle the platinum pieces for 15 minutes. Place platinum castings in the kiln on a clean alumina ceramic block. Leave the casting in the kiln at initial temperature for 45 minutes. Allow the platinum pieces to cool in the furnace. Pickle pieces again for 15 minutes.
Preparing Platinum for Polishing
Hammering tools may be constructed from used stone setting burrs. Please find below a method of producing a hammering tool.
Heat the burr to cherry red for approximately one half minute to one minute and allow to air cool. Cut off the tapered end or culet of the burr. Bend the shank end of the burr at about a 30 degree angle.
The surface of platinum castings should be hammered with a light touch, using multi-directional movements. Use wintergreen oil or household oil to keep the surface of the platinum lubricated and smooth.
For burnishing, a tungsten or tungsten carbide burnisher will be necessary. A piece of 1/8″ outside diameter by 1 1/2″ in length tungsten or tungsten carbide is tapered on one end, much like a sharpened pencil. Have the narrowed tip left rounded rather than blunt. A high polished surface is desired. To taper and polish the tungsten burnisher, a diamond grinding wheel and diamond polishing powders are required. It may be cheaper to use a machine shop for this project, due to the high cost of supplies for grinding and polishing tungsten/carbide.
The surface of platinum castings should be burnished multi-directionally, using wintergreen or household oil. Heavy pressure can be used. This can be done in the hand-piece of a flex shaft. For quicker results, put the burnisher in a chuck adapter and use on a polishing lathe.
Always polish the platinum components before connecting to gold. This keeps the gold from being polished away, which can happen because of the difference in density between the two metals. Pre-polishing also allows defects in the castings to be recognized and pits to be filled by welding prior to assembly.
Assembly of Platinum to Gold
The platinum and gold pieces should fit together as closely as is possible. Cover the karated gold pieces with boric acid and alcohol glaze solution. Always use a karat gold brazing filler material to match the color of the gold used. The work surface should be kept clean and free of any residue from filing, sawing or polishing.
Concentrate the torch toward the karated gold side. Clean off any filler material that runs onto the platinum side before proceeding to the next joint to be brazed. A brazing stop-off may be used to minimize filler material running off into designs or on to the platinum component. Air cool the piece before pickling. Pickle 15 minutes after filing using emery paper. Clean out files with a file card or use separate files for gold and platinum. Also use separate sheets of emery paper for gold and platinum.
Welding and Sizing With Platinum
Always use UV protective eyewear when brazing or welding on platinum. A #5 welding lense is adequate for brazing, while a #10 or higher lense is required for welding or melting platinum.
Although oxygen/natural gas or propane is adequate for brazing, using a hydrogen gas torch provides a hotter and cleaner gas. Below you will find a procedure for filling pits in platinum castings.
Clean out pitted area completely by grinding into the pit with a high speed bur, then pickle for 15 minuntes. Start with a coarser grit and progress to a finer one.
Stainless steel shot can be used for the burnishing process in the tumbling operation. Here it is important to consider the amount of impingement that is being applied to the piece. The amplitude of the vibratory tumblers should be reduced to minimize impingement. The shot shape will also affect the degree of impingement imparted on a piece. Pins tend to produce a better burnishing action than most other shapes. If a barrel tumbler is being used, reduce the rotational speed to cut down on the degree of impingement. Adding a polishing powder to the burnishing process will help improve the overall finish.
The time cycles in polishing platinum are going to be a matter of trial and error in order to produce the best results. But once you have established what works best in your machines, the process should be highly repeatable. As a general rule, the cycle times for platinum will be longer than those for gold and silver.