Cast of characters

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.

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.