Platinum Consideration Factors

Jurgen J Maerz of the Platinum Guild International USA outlines factors to consider when adding platinum to your line of manufactured jewelry.

Technical education is the key successfully manufacturing platinum jewelry. Platinum is often regarded as a difficult metal to work with, however once you understand the capabilities as well as the limitations of this metal you will find working with it a pleasure.

Platinum is not more difficult to work with than any other precious metal, but it is very different. This difference created a need for education on all levels, from designer to end-user. The Platinum Guild International (PGI), with six offices worldwide, is educating as many jewelers and consumers as possible about platinum. Through sales training and technical training as well as articles in trade publications, the word is spreading: platinum is here to stay, let’s join the platinum wave.

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It is possible to make things out of platinum that would be impossible to even attempt in anything else. What you need is an understanding of platinum’s metal properties, its malleability and ductility and behavior when heat is applied. Add to this your skill as a craftsman and you should have no problems at all.

Alloying platinum

Before platinum can be used in jewelry making, it has to be alloyed to create the metal most suitable for a specific application. Platinum can be alloyed with a multitude of metals to create a harder, more usable alloy. platinum alloys range in purity from Pt 950 to Pt 900 and Pt 850. Pt950 contains 950 parts per 1000 of platinum and 50 parts per 1000 of another metal. Pt900 contains 900 parts per 1000 and 100 parts of one or more other metals. Pt g50 is not very common and is usually found in chain product.

Alloying platinum with different metals creates a variety of properties that make platinum extremely versatile. Adding five per cent ruthenium creates an alloy suitable for machining and faceting on a lathe. Many wedding bands are made this way. A five per cent addition of cobalt to platinum creates a very fine casting alloy. This alloy is hard and strong, yet very fluid and capable of filling very fine detail during the casting process. Adding tungsten will create a springy alloy that is generally used for findings. There are many more specialty alloys on the market, not to mention proprietary alloys that manufacturers create to make jewelry such as tension rings.

Manufacturing Methods

Platinum jewelry can be manufactured in many ways, the decision is whether to fabricate, cast or die-strike the pieces. This will lead to a discussion of which alloy to employ.

Many wedding bands are fabricated by machining platinum from tubing. The recommended alloy for this manufacturing method in the US is platinum/ruthenium (Pt/Ru), a hard and flexible alloy. Ruthenium is another platinum group metal. Made into platinum tubing, this alloy is usually cut in “Swiss machines” or on a lathe, using diamond-cutting tools, to make wedding bands of many design variations. Tubing can be made several ways, ranging from extruding to pressing from a washer like disc. Most tubing is seamless. The wedding bands are then sliced off the tube and are shaped and cut to create the various designs.

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Casting can be done with several alloy combinations, of which platinum/cobalt (Pt/Co) and platinum/iridium (Pt/lr) are the most common. In the Pt/Co alloy, the cobalt acts as a grain refiner and gives this alloy the ability to fill very fine detail. Casting employs the lost wax process and can be accomplished with either the torch or an induction machine. Other alloy combinations can also be cast.

The extremely high melting point of platinum makes it possible to do bi-metal casting, where another metal is cast onto a finished platinum piece, thus creating color contrast.

When casting platinum with a torch, hydrogen/oxygen is the preferred fuel combination for the melt. Acetylene is not useful for melting platinum as it expels carbon in the flame and carbon will contaminate the metal through absorption. While it is very hot and melts the metal rapidly, platinum will become brittle if acetylene is being used’ Propane/oxygen can be employed successfully. It is also important to get the proper torch for this job.

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Due to the characteristics of platinum, the high temperatures and the variety of applications, there is a substantial learning curve to become successful with induction casting platinum. It is recommended that small manufacturers send casting to casting houses.

Modern laser equipment has proven to be very helpful in removing defects such as excess porosity on a platinum casting. It also allows the repairing or welding close to stones, without causing damage to them. With a laser welder, repairs on vintage jewelry can be performed that are not possible with conventional methods.

Fabricating platinum jewelry has many benefits. The high melting temperature of the metal will make working with the finest wires possible. Its unparalleled strength makes platinum the ideal metal to securely hold stones in mountings, and the luster that can be achieved by properly polishing platinum is second to none.

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Die striking is used to make anything from findings to light weight earrings and more. Platinum iridium alloys are very suitable for this. Platinum’s density means a much thinner sheet of metal can be used and still be as strong as the heavier gauge necessary to do the same piece in gold.

Platinum is considered a “dead metal”, which means it holds the shape, or position it is placed in, without springiness. This is of great advantage for prong setting. Once pushed in place, the prongs will securely hold stones in place. Like all metals platinum will scratch during wear, but there is no metal loss when scratching occurs. Therefore engravings will not fade, and prongs and shanks will last for generations.

Platinum Finishing

The finishing of platinum jewelry requires some preparation. It takes several additional steps to finish platinum compared with gold or silver. When platinum is used in conjunction with gold or other metals, the platinum must be polished first, as otherwise the other metals will be over polished. The best way to polish platinum is to use the compounds that are made for this purpose. Go from a coarse grit to an ever finer polish, 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 luster, which will last for a very long time, but also lends itself to many types of surface finishes.

Bench jewelers who have the skill to fabricate jewelry will have no trouble applying that skill to working with platinum. Platinum is a pleasure to be hold, but can be very unforgiving, if one does not take the time to learn its properties.

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Platinum is the most precious of all precious metals because of its high purity, rarity and other characteristics. Inert to most acids and oxides, and hypoallergenic, it is the ideal metal for jewelry. Platinum is here to stay and it is a very good decision to join the platinum wave. Remember, platinum is not difficult- it is different.

By Jurgen J Maerz
© Bench Magazine 2002 Winter
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BENCH Magazine is devoted to the Bench Jeweler in retail jewelry stores and small trade shops.
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Jurgen J Maez is the director of technical education at the PGI USA. More technical information can be found at www.pgi-platinum-tech.com or through your questions by e-mail at iurgen@Pgiusa.com
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