This palladium bench guide reviews the working characteristics of palladium for the bench staff and provides an overview of the advantages and benefits of palladium jewelry for managers, sales professionals, and consumers. Here, find some commonly encountered palladium jewelry scenarios and the related materials available in the industry today.
950 Palladium Alloys
Palladium is alloyed for use in jewelry (Fig.1). Standard alloys contain 950 parts of palladium and 50 parts of other metals (this portion of the alloy may vary among suppliers). The most common alloy component in the United States is ruthenium, which, along with palladium, belongs to the platinum group of noble metals. Ruthenium usually accounts for about 4.8 percent of the 5 percent mixture, leaving room for trace metals that improve working, wearing, or casting. The common alloy ingredient used in China, where palladium jewelry is mass produced, is 950 parts palladium and the balance copper.
Palladium or platinum solder is used for soldering 950 palladium alloys. Palladium solder is usually supplied in hard, medium, and easy grades. The general flow temperatures for them are: hard, 2,365°F; medium, 2,210°F; and easy, 2,005°F.
Platinum 950 solders are made with gold, silver or platinum, and palladium. More palladium and platinum is present in the “harder” solders—those with higher melting points. Platinum solders used for soldering palladium are 1,300 (hard), 1,200 (medium), and 1,100 (easy), and they have the same general melt and flow ranges as listed above for palladium solders.
When soldering a palladium assembly (Fig. 2), do not use fire-coating solution or flux. Use welding lenses rated No. 5 or darker for eye protection. Palladium loses its polished luster during the soldering process, in much the same way as karat gold. However, palladium’s luster is easily restored through minor repolishing. Palladium solder is available in hard-, medium-, and easy-flowing temperatures. You can also use 1,300, 1,200, and 1,100 platinum solder, which has similar melting points and composition.
When soldering karat gold to palladium, fire-coat the assembly as you would with gold. Standard gold soldering flux and easy-flowing gold solders should also be used. The link being soldered to the pendant in Fig. 2 was first tacked in place using an ABI Tack II.
To position palladium pieces for soldering, place them on a platinum soldering block or hold them with high-heat cross-locking tweezers.
Use a high-heat soldering block for annealing (Fig. 3) and always use eye protection. Welding lenses with a rating of No. 5 are used to shield harmful white light. Bring the piece being annealed to an orange color, hold it for about 20 seconds, and allow it to cool. (The wire being annealed in Fig. 3 is from Hoover & Strong.)
Soldering Settings and Retipping Prongs
Easy palladium solder (shown in Fig. 4) or 1,000 or 1,100 platinum solder are all suitable for soldering settings in place. Direct soldering procedures are used. When prongs wear down, it is recommended to replace the prong or setting. It’s best not to risk soldering new prong tips on prongs if you’re uncertain of the stability or identification of the set stone. However, if it’s documented that the set gemstone is stable, untreated, and can withstand the heat of soldering temperatures, new prong tips can be made of palladium and then soldered in place using hard white gold solder. (Easy solder, ring, and setting in Fig. 4 are from R Findings.)
Fig. 5 shows the soldering process through a No. 5 welding lens. A torch tip with no vents and an opening of about 1.2 mm is used to directly heat the joint. The torch is positioned so the hottest part of the flame (the area about ¼ inch beyond the blue cone) directly heats the joint. The torch is moved slowly from side to side. Because of the low thermoconductivity of palladium, the heat is concentrated in this specific area. The ring is heated and the solder melted into the joint. (Ring was cast by TechForm, Portland, Ore., using Johnson Matthey 950 Pd.
When soldering 950 palladium to karat gold (Fig. 6), it’s important that cadmium-free solders are used. If not, the resulting joint will fail under normal wear.
Sizing 950 Palladium Rings
For sizing rings up or down, they are cut at the bottom portion of the shank, and the appropriate amount of metal is removed or included. The ends of the shank should be precisely rejoined with no visible gaps or spaces. To solder the joint, place it on a ceramic platinum soldering block or hold with high-heat cross-locking tweezers. Use hard palladium solder or 1,300 platinum solder. Directly heat the joint using an oxidizing flame to melt and flow the solder (Fig. 7). Use No. 5 or higher welding lenses for eye protection.
When 950 palladium alloys are heated to high-heat ring-soldering temperatures, they may develop a bluish-purple surface discoloration (Fig. 8). It’s easily removed by briefly and mildly heating the piece with a neutral flame. A neutral flame has equal parts of gas and oxygen. The surface discoloration can also be removed by using fine abrasives. (Ring and setting are from R-Findings.)
Ring in Fig. 9 is made from Johnson Matthey’s palladium alloy and contains 950 parts palladium, about 50 parts ruthenium, and a small amount of gallium. The appropriate quality marking is 950Pd.
Palladium, like platinum, requires high heat when casting, so use of platinum casting materials and equipment is necessary (Fig. 10). Palladium absorbs gas when melted and re-leases it upon solidification. When palladium solidifies, gases can be trapped, resulting in pieces that contain gas porosity. For the best results and to minimize gas porosity when casting, use an induction melting-casting machine with a sealed melt chamber and an argon cover. Palladium is best cast by properly equipped casting facilities with experienced personnel. (Fig. 10 is courtesy of TechForm Casting, Portland, Ore.)
A laser welder works with palladium (Fig. 11), but the technique differs from laser-welding gold or platinum. When filling voids and pits or building up joints with a laser, start by directing pulses of energy directly into the void. This will melt the bottom, exposing fresh metal from which to build. For best results, use small-diameter filler wire, narrow joints, and your laser’s pulse-shaping feature. You can use this technique to avoid overheating the material, by beginning the settings with high laser intensity and then incrementally reducing laser power once the melting point has been reached. Pulse shaping can also reduce cracking in the metal, which can occur during quick cooling of a weld, important for 950 palladium alloys. (Fig. 11 features Brenda Warburton, Austin & Warburton.)
Setting gemstones in palladium is similar to setting in platinum. When bending and forming prongs or bezels to secure gemstones, the metal does not spring back as with most white gold alloys. This is referred to as dead-setting. Palladium’s purity precludes prong failure due to corrosion.
Prefinishing, Finishing and Polishing
Prefinishing and polishing (Fig. 12) require fewer steps to accomplish compared with platinum, and an extra step or two compared with white gold. To finish a casting, begin with No. 4 cut files and finish with No. 6 cut or fine abrasive sanding sticks. Grits from 400 to 1,200 are ideal. After using abrasives of 1,200 grit, polish the piece with Bendicks white rouge. For the final step in polishing, use a 6,000-grit white rouge. For best results, use files, abrasives, and polishing materials dedicated for palladium. Palladium alloys brighten during tumbling and magnetic finishing procedures. Magnetic finishing also restores palladium’s polished luster after soldering procedures. No rhodium or other plating is required to improve the color of 950 palladium alloys.
Tools and Equipment
For best results when working with palladium, use palladium-dedicated files, sanding sticks, rotary abrasive materials, and polishing wheels. Keep your workbench clean and free of debris from gold and platinum projects. Use high-heat soldering tweezers and pads and always use eye protection.
Iodine can be used to detect the difference between palladium, platinum, and white gold. Place a drop on the cleaned surface of the unknown white metal. As the small drop of iodine evaporates and dries, it may take on a body color that will assist in detection of the metal. Here are the most common reactions: On 950 palladium, iodine turns black (Fig. 13); on 900 and 950 platinum, iodine is mostly colorless; on 14k and 18k white gold (below a rhodium-plated surface), iodine turns brownish. These reactions will not occur on a rhodium-plated finish. The rhodium must be removed at the location where the test drop is placed. (Ring in Fig. 13 is by Novell.)
Cost Analysis—Palladium, 14k White Gold, and Platinum
At press time, market prices (per ounce) for metals were: palladium, $324 ($16.20 per pennyweight); platinum, $1,120 ($56 per pennyweight); gold, $621; 18k gold, $465.75 ($23.28 per pennyweight); 14k gold, $363.29 ($18.16 per pennyweight). Since metal supplier markups vary, they are not included in this analysis.
Considerations for Palladium Refining
For the best return when refining palladium, keep palladium filings, bench sweeps, and polishing debris separate from the same containing other precious metals. Also, keep palladium hard scrap separate from other precious hard scrap. This will maximize your return and speed the settlement.