The technical considerations involved when working with Platinum and gold in combination are considerable. The designer who sets out to create a piece without full knowledge of these metals' properties and individual behavior is certainly headed for surprises.

You will find, as I once did, that such experiments can be extremely expensive.

The Problems with Miragé
Before I go into the technical differences between platinum and 18-karat gold, I would like to tell you a story which I think will illustrate very well what can happen to jewelers when their ideas are more ambitious than their bench skills. This is about the development of my signature design, the Miragé, and what happened when I decided to use platinum instead of 18-karat white gold in the design.

In the early 1980s, when Paul Klecka Inc. was still a manufacturing retailer, I was intrigued by the optical effects created by the intersecting planes of glass on the sheathed buildings which were then on the cutting edge of commercial architecture and were being built all around me in downtown Chicago. I wanted to create that same sort of reflective illusion for jewelry, but it wasn't until 1985 that I had both the resources and the technical ability to do it. The result was the Paul Klecka Miragé.

Using diamonds and 18-karat white gold, the first Miragé pieces I created were earrings and cufflinks.

The optical illusion that I was looking for, the visual doubling of the diamonds, was created by the highly-polished plane of white metal set at just the right angle. I was satisfied by the effect created by my design, and when in 1989 I won the De Beers Diamonds Today award with these two designs, I was convinced of Miragé ´s commercial potential.  There was only one problem.

Although the 18-karat white gold reflected the diamonds nicely, giving me the doubling effect I wanted, the slightly dark tint of 18-karat white gold was making the reflection of our F- color diamonds appear at least three grades lower; at best I to J. For me, this was a real aesthetic problem. The obvious white metal alternative was platinum, but I wasn't familiar with the metal, and I was hesitant to try it. The emergence of the Platinum Guild, however, forced my hand. As we all know, the Platinum Guild's influence really began to be felt in our industry in the early 1990's. Being market-oriented, when I saw that the Platinum Guild's efforts were creating a genuine consumer response, I decided that it was time to try platinum, and the appropriate starting point was with Miragé. The results of my attempts were decidedly mixed.

The first Miragé design I created using platinum in place of 18-karat white gold was the disk earring, and my success with it lead me to think that working with platinum was easier than I had thought; and platinum and 18-karat gold were compatible.

Why? Because I had beginner's luck in the way I had designed the piece. The only meeting of the metals involved in the disk earring was a one millimeter edging platinum wire joined to the half-millimeter disk to visually thicken the edge, and this was not enough contact to create the stress between the two metals which was later to cause me many headaches.

But the headaches began soon enough. Flush with my success introducing platinum into the Miragé, disk earring design, I tried to introduce it into fashion rings and wedding band designs. Disaster. Months of work were lost, not to mention orders.  The problem that we had was a heartbreaking one because it only appeared with the final polish. Suddenly, in a piece which had appeared structurally sound in every way, tiny fissures would appear in the metals, especially the 18-karat gold. Time after time, these pottery-like cracks would appear with the final polish. With each splintered piece we scrapped, it became clear that we had a systemic problem, and if we were going to keep customers, we were going to have to find a solution fast. So, we started searching.  We began the process by trying to eliminate possible causes. Was it a defect in our casting gold? A defect in the platinum? A technical issue having to do with our assembly procedures? Or could the design of our model be at fault? Of course, the caster blamed the jeweler, the jeweler blamed the caster, they all blamed me, and so on. After much information-gathering and with the cooperation of numerous industry colleagues and several of our suppliers, we determined that the source of our cracking problem was entirely in-house. When we added a jeweler to our bench staff who had extensive experience working with platinum, it was clear that half of our difficulty had been caused by inexperience in proper handling of the metals. The other half, unfortunately, was created by my design.

What we discovered through our research is that the way in which we had been interpreting my designs was fundamentally flawed given the two metals' distinct characteristics. Not only were we attempting to combine them in incompatible proportions, we were also trying to join them in a way which was guaranteed to create the stress fractures which were driving us crazy.

The changes we made were: First, we made the platinum elements in each design much more delicate, so that their thickness would generally be less than that of the gold components.

It was apparent that because platinum and gold respond very differently to heating and cooling, without controlled cooling after soldering, the platinum elements in each design would create enough stress on the gold to literally tear it apart. By reducing the volume ratio of platinum elements to gold, we greatly reduced this problem.

Second, we changed our method of bonding the metals from sandwiching, in which the internal stress was distributed laterally throughout the piece, to an end-to-end joining, which distributed the stress perpendicular to the bonded area. This change accomplished two things. First, changing the direction of the stress in the piece, and distributing it throughout the design greatly eliminated and redistributed the amount of pressure put on the gold during cooling, resulting in a much improved success rate.

Second, substantially diminishing the amount of contact between platinum and gold also minimized the amount of stress at the joint.

These changes created a difference of as much as five to one in the amount of contact between the two metals, which therefore reduced the possibility of stress by approximately the same ratio.

Today, our bench staff has had enough experience joining platinum and gold that the sandwich method which had failed us earlier is now possible to execute. The Miragé experiment taught us a great deal about the complexities of working with 18-karat gold and platinum in the same piece. Although our initial results were not promising, we now know the two metals' technical parameters and have been able to find ways to successfully join them. But it would have been nice not to have discovered these processes by trial and error. This is not to say that joining platinum and gold still does not present us with challenges. Of those we still have plenty. Below is a summary of the technical considerations of which any jeweler must be aware when joining platinum and 18-karat gold.

Technical Issues in Joining Platinum and 18-Karat Gold
Rather than fighting against the behavior of gold and platinum, learn to exploit their differences in characteristics and behavior to your advantage. First of all, your design must reflect a knowledge of how the metals will respond to each other in combination, and must take into account numerous issues that can be aligned to your advantage.

Success begins with good housekeeping. Contamination is probably the leading reason for failure in joining platinum and gold, so in our shop, we make an effort to completely separate the gold and platinum at every stage of the manufacturing process.

Let's go step-by-step through typical shop procedures and review potential problem areas in working with platinum and gold.

Silica contamination
The first step after casting platinum is to completely remove any trace of investment compound from the raw casting. Silica can create cracking and inclusions that are nearly impossible to remove later. And it doesn't take much to cause a problem down the line.

TechForm Casting of Portland Ore., suggests that a cold bath of hydrofluoric acid will dissolve any silica investment and will not harm the platinum.

Steel contamination
It is inevitable that metallic contamination will occur during routine shop procedures.  The metal will contact various steels during rolling, hammering, sawing, filing, grinding, and drilling, and this will create cracking and inclusions if not removed.

Precious metal contamination
It seems ironic to mention in a paper about combining platinum with other metals, but gold, silver and copper will also create problems if not handled properly. Since these metals do not alloy but instead form compounds with platinum, the result of contamination will be cracking and inclusions in the platinum elements. When combining platinum with other precious materials, we certainly want all elements of the design to be clean and unblemished. A nitric acid bath will remove any non-ferrous contaminants from the platinum surface.

Heating and cooling behavior
As I mentioned earlier, we experienced tragedy in the heating and cooling of combination pieces because we were not attentive to the great difference in the expansion coefficients of platinum and gold. Care must be taken not to quench a combination piece, but instead allow it to air cool in a slow, controlled manner, thereby minimizing the stress at the joint. Overheating will produce a similar effect upon the gold, breaking down the crystalline structure and causing stress cracks to form.

A set of solder picks and tweezers should be dedicated for platinum use only, and should be made of tungsten, which has a higher melting temperature than platinum.

Assembly techniques
Reference the original article for a detailed series of different assembly techniques.

Welding and Soldering
In the conventional process of joining platinum and gold elements, there are two basic rules to follow which reflect the behavior and characteristics of each metal. If you are joining platinum and 22-karat or higher gold alloys, platinum techniques are used to form the weld. No flux is needed, since both materials are pure enough to resist oxidation. In general, temperatures over 1000° C are needed to complete the weld.

If you are joining platinum and 18-karat gold, however, you need to use basic gold techniques, i.e., temperatures generally well below 1000° C, the use of a solder with a lower melting point than the two metals to be joined, and the use of flux to prevent oxidation of the gold and polish.

The different hardness of gold and platinum
If a platinum and 18-karat gold combination piece is polished in the wrong direction, from the gold surface towards the joint, the wheel will pull the gold over the joint, smearing the line of demarcation. The key here is precision. Pre-polish all platinum elements, avoid sloppy file strokes, wrong wheel speeds and cross-transfer of abrasives.

Conclusion: Words of Encouragement
Know your metals' properties;
Design for your metals' properties;
Exploit these differences to your advantage. Proper preparation is crucial to the successful joining of platinum and gold. Your time invested on the front end will be repaid many times over in the success of the final piece.

V3N5

Paul Klecka
Paul Klecka Design
Platinum and 18-Karat Gold…Oil and Water?

This is an abbreviated version of the original work. For full technical details, please consult the original paper.