Working with platinum: It’s not difficult, just different

by charlene_voisin | December 1, 2012 9:00 am

By Jurgen J. Maerz

[1]

The price of platinum compared to gold has helped turn more consumers on to taking their jewellery up a notch, particularly in the bridal category. And while many might still prefer gold over the naturally white precious metal, the category as a whole is growing, especially in markets like China. Canadians, however, have traditionally embraced it and continue to do so.

To gain a better understanding of how to sell platinum—which is rare and relatively pure as an alloy—let’s take a closer look at its characteristics.

Cast of characters

[2]

Platinum is not more difficult to work with than other precious metals, but it is very different. As such, there is a need for education on all levels—from manufacturer and designer to sales staff and end user.

Platinum jewellery can be manufactured in many ways, ranging from the unique handmade one-of-a-kind piece to die-struck earrings or cast mountings. For manufacturing, the decision will centre on whether to fabricate, cast, or die-strike the pieces. This will inevitably lead to a discussion of which alloy to use. These days, a mix of platinum and ruthenium (Pt/Ru), which is also a platinum group metal (PGM), is the combination of choice for wedding band manufacturers. Tubing is usually cut using engraving machines with diamond tools or Swiss machines with rotating knives, allowing countless design variations.

Platinum/cobalt (Pt/Co) and platinum/iridium (Pt/Ir) are the most common alloys for casting. In the case of Pt/Co, cobalt acts as a grain refiner and gives this alloy the ability to fill very fine detail. Pt/Ir is acceptable when the iridium and platinum content is 100 and 900, respectively. Other combinations using iridium are too soft and can lead to consumer dissatisfaction, as the jewellery tends to deform and scratch easily.

[3]

Casting employs the lost-wax process and can be accomplished with either a torch or an induction machine, although the latter can be more reliable. Since it can be a considerable investment, you may want to consider leasing an induction machine, thus overcoming the capital outlay.

Given platinum’s unique characteristics, the high temperatures required to work with it, and the variety of applications, there is a substantial learning curve to successfully cast this metal. As such, small manufacturers may want to consider using a casting house. This can also help guarantee a better product at a reasonable cost, since the investment mix, as well as the alloy, crucible, and gating system, may affect the casting’s quality.

In addition, there are many forms of casting defects that can occur, such as no-fills, porosity, and cracking. Therefore, implementing a process control system with repeatable steps should be considered to eliminate them. Modern laser equipment has proven very helpful in removing defects like excess porosity, as well as when repairing vintage jewellery, since the original solder may be unknown. Laser welders may also be used near stones without fear of damaging them.

Fabricating platinum jewellery has many benefits. For instance, the metal’s high melting temperature makes it possible to create the finest wires; its strength can allow stones to be securely held in mountings; and properly polishing platinum can achieve a very high lustre.

[4]

Die striking is used to make anything from findings to lightweight earrings and more. Here, a platinum/iridium alloy is a viable option. Given platinum’s density, a much thinner sheet of metal can be used and still be as strong as the heavier gauge necessary to strike the same piece in gold. Platinum is considered a ‘dead metal,’ meaning it holds its shape or the position in which it is placed without springiness. This is of great advantage for prong-set stones, which are securely held once the claws are pushed in place. In addition, the metal’s density means it will not wear down as quickly as other precious metals, so prongs and shanks can last for generations. This is one of the attributes that helps make platinum jewellery the ideal heirloom.

The finishing of platinum jewellery requires some preparation and several additional steps, compared to gold and silver. For instance, platinum prongs on a gold ring must be polished first to avoid over-polishing the band. This is particularly important for sales associates who offer to polish a customer’s ring.

To polish platinum, only use the compounds that are made for this purpose. Also, it is critical to start with a course grit followed by ever-finer grits until all scratches are invisible and the piece is ready for the final buffing. This extra effort is well worth the result. Platinum can be polished to a very high lustre that can last for a very long time. In larger operations, tumblers and other mass-finishing methods are being used to save time. Platinum also lends itself to many types of surface finishes, such as sandblasting and satin-finish diamond cutting. While platinum is very tough, it does scratch during wear, as do all metals. However, the main difference with platinum in this respect is very little metal is removed. Rather, it is displaced. Platinum’s properties also allow engravings to remain sharp longer.

At the bench

Often rings need to be sized, serviced, or heads added or replaced, requiring bench jewellers fully understand the metal’s nuances. Here are a few dos and don’ts that may be helpful:

• Always make sure to use dark welding glasses when soldering or melting platinum;
• Never solder or weld platinum using acetylene, but rather natural gas, propane, or hydrogen;
• Do not use flux when soldering platinum, as it can be absorbed and contaminate the metal;
• Avoid contaminating platinum by working on a clean bench;
• Keep a set of files to be used only on platinum pieces to reduce the risk of contamination;
• Do not use charcoal soldering surfaces;
• Only use tungsten soldering picks;
• Never use platinum solder or torch-weld near gemstones to avoid burning them;
• Laser welders can be used on platinum;
• White gold solder is safe, as long as it does not exceed two parts per 1000;
• When polishing and finishing platinum, remember to ensure there are no scratches in the metal before applying the lustre. It is good practice to remove scratches with a fine sanding and polishing paper before the final buffing.

Technical education is key to successfully working with platinum, along with conveying its benefits to consumers. Understanding its capabilities, as well as limitations is of the utmost importance. Annual events such as the Santa Fe Symposium held in Albuquerque, N.M., present opportunities to learn from industry experts and stay informed about the latest technology and techniques. For more see What is platinum?[5]

Jurgen J. Maerz is an independent industry consultant and owner of Jurgen Maerz, Jewelry Consulting LLC. In the industry since 1961, he is recognized as an expert in the world of platinum. Maerz has published two award-winning books on platinum and has presented seminars on the subject all over the world. He can be contacted via e-mail at jurgen.maerz.consulting@gmail.com[6].

Source URL: https://www.jewellerybusiness.com/features/working-with-platinum-its-not-difficult-just-different/

---