Platinum's popularity in the United States is on the rise, and so is the desire of jewelers to be able to master this precious metal. One of the most common misconceptions is that platinum is "hard to work with." Working with platinum is not difficult. It requires a different approach with respect to most traditional goldsmithing techniques, and it will force you to break some of your habits around the work bench.

THE BASICS:

Bench cleanliness
It can't be stressed enough that cleanliness is the law and foremost rule to live by when processing platinum. Platinum is easily contaminated with almost anything that you use around your work bench and jewelry shop. Once contaminated, platinum can only be reclaimed through costly refining.
If the limitation of space in your work shop doesn't permit separate platinum-only benches, clean your work bench and drawer thoroughly before starting your work on the platinum piece. Remove all tools that you use on gold and silver from the surface of the bench and replace them with your set of platinum-only tools.

Drawing:
Be sure that the draw plate is free of residue from previous operations and has a polished surface. Steel plates are not recommended. Tungsten-carbide, corundum or diamond tools are called for to ensure a precise cross-section of your wire or tubing.

Polishing:
Cross-contamination from gold and silver particles can be avoided by using specially marked wheels and attachments. Therefore, one set of brushes, felts, buffing wheels and emery wheels should be dedicated for platinum use.

Rolling:
Prior to any platinum rolling operation, clean the rollers with alcohol. After each rolling step and before annealing, the platinum piece should always be treated in a 10% nitric acid solution to prevent any possible damage by non-ferrous impurities. A bath of sodium sulfide acid before heating and melting, followed by pickling, will remove any ferrous metal contaminants from the surface.

The right alloy
There are a variety of platinum alloy combinations that find use around the world. Each particular one has been composed by metallurgists and metal experts because it has certain properties that make it particularly suitable when being used to perform a specific task. So, before you get started, take some time to analyze which production steps your design will require and based on those findings, choose the alloy that will accommodate your needs best.

Plan your design
Instead of working with one large platinum casting, try to break the piece down to smaller individual components, as it is much easier to get good casting results for small pieces. Plan your brazing seams and joining sections such that they are hidden, and not subject to the most attention. Assemble and finish the platinum components completely before joining them with karat gold segments. Keep the specific gravity of platinum in mind! Don't design pieces that are too large, too heavy or too expensive to ever be sold. Use welding techniques over brazing whenever the piece allows.

Switching gears
If your workshop space allows it, have one bench strictly designated for work with platinum. Switching physically from the "gold bench" to the "platinum bench" will also help you focus on switching gears between the different manufacturing techniques that the properties of the metals dictate.

Appropriate Tools
Every piece of platinum jewelry is only as good as the worst tool that was used to produce it. Utilizing the right tool is important since this metal requires special tools which can withstand the higher brazing and welding temperatures. During all cutting and shearing applications it is important that all cutting edges are clean, polished and sharp. Generally speaking, tungsten tools or diamond-tipped tools are superior to steel, as they produce faster and more accurate results. For all cutting and grinding processes generous lubrication is highly recommended.

Be Creative
Sometimes you might have "a vision" for a new jewelry design, but you can't think of an immediate solution for the challenges the manufacturing process entails. Don't drop the idea because "it's too difficult!" Keep the thought in the back of your mind, juggle it around and be open for a different approach. The point is, if you are hatching the idea long enough you will eventually find a solution. Perseverance and patience are virtues required for successful platinum designs.

No Shortcuts
The same perseverance that is part of the innovative design process is also called for when finishing platinum. Bright mirror polished surfaces are visually appealing. Unfortunately, achieving this high goal has its price because the steps that lead to it are very labor intensive (about three times higher than silver and gold) and require disciplined, progressive use of increasingly finer abrasive paper and polishing compounds. Following these systematic steps will result in the desired surface qualities; cutting corners will find you spending overtime at the bench pin. A final consideration discussing the "platinum basics" is striving for knowledge. In order to stay atop of all the innovations and developments, use the resources that industry associations offer. Time spent will reward you with valuable information and knowledge.

The Tricks:

Wedge angle principles
Some of the most common tools for daily jewelry applications will require some modifications to work equally well for work on platinum.  This holds particular truth with cutting tools. A high surface resistance metal (platinum) will require an extremely high energy level when working with a wide wedge angle. A small angle will wear out the tool soon and is more difficult to guide.

Cutting angle principles
In order to achieve a small point angle for best cutting efficiency, reduce the wedge angle of the cutting tool and keep the clearance angle shallow.

Change the angle of your gravers
Let's say you need to cut a groove into a ring. Often times, it is faster to use a graver instead of a milling cutter. Most gravers from your tool suppliers come in sharpening angles for traditional gold and silver applications (commonly 35°-40°). Due to platinum's toughness, though, it is necessary to reduce the sharpening angle to 15°. Make sure that the graver surface is clean and high polished.

15° angle for platinum
Not only the cutting edge of the tool, but also the angle in which you should introduce the tool to the metal surface (rake angle) is different from traditional gold- and silver cutting. A large rake angle will allow you to achieve a fine cut with moderate force.

Modify your drill bits
Depending on the amount of drilling that is performed in your jewelry shop, you can either take the time to modify your regular drill bits, or you can reach deeper into your pockets and buy those specialty platinum drill bits. For all important precision cutting operations with no tolerance for off-center fixing, it is recommended to use diamond tipped drills.
Also, it is advisable to work with pilot holes, ideally in combination with a modified drill bit at a cutting angle of about l5°.
You should not work with high rotational speed when drilling platinum. Since platinum is a high surface resistance metal, excessive speed will increase your chances of getting the drill bit stuck or wearing it out too soon. So, generous lubrication and a lower rotational speed will allow the drill to transport the drill grindings away from the drill bit shaft.

Bendable files
Sometimes it is the "little helper tools" that make your life a lot easier. Some special needle files have a flexible core under the hardened surface which allows them to bend into the shape needed for hard-to-reach spots. This permits filing at a relative quick rate without worrying about marring surrounding prongs, or other components.

Frequent saw blade changes
Depending on the hardness of the metal that you are cutting, you have to choose the appropriate saw blade. A hard metal requires a large wedge angle to prevent the teeth from breaking. A soft alloy calls for a blade with a larger clearance angle to allow all particles that were cut during the last stroke of the saw to be accommodated in the voids. If the voids are not big enough the particles get stuck and the saw blade is jammed. Bee's wax lubrication supports the transport of the cut particles from the voids and reduces the dragging friction. When cutting thin cross-sections of sheet or tubing, it is necessary to work with a fine-toothed saw blade, because large teeth get hooked on the sheet or tubing and cause the piece to bend. For all normal cutting operations that work on pull (teeth facing down), you will find that depending on the angle in which you introduce the saw teeth to the metal piece, it will be easier or more difficult to cut the piece. Experiment and find out which angle works best for the particular alloy you are working with. Due to platinum's "stickiness," the saw blades dull much faster compared to other metals. Change the blades often to avoid breakage. Keep in mind that only one undetected saw tooth stuck in the work piece when the piece gets heated is enough contaminate the whole piece permanently.

Re-tipping prongs
Don't repair a setting, or re-tip a prong with a gem stone in place. Even diamonds will be damaged or destroyed by the temperatures required for brazing platinum. Make it a rule of thumb to remove all gemstones that will be closer than half an inch to the heat source.

Groove the pusher
Platinum is a setting-friendly metal, as it easily bends. Once a prong is pushed on a stone it stays there, not showing the springiness you know from gold.  Since the finish on your platinum piece is already completed when you are starting the setting process, avoid leaving tool marks on the settings. Cut or file a groove into your prong pusher that can accommodate the width of the prong. Shape a negative cylindrical shape for round wire prongs, or a squarish groove for flat wire prongs. Keep your pushers clean and high-polished.

Magnetic platinum-cobalt
When working with platinum cobalt, keep in mind that this platinum alloy is slightly magnetic. If you use a magnet to separate broken saw blades from filings in the working tray, you will catch the platinum saw dust too. Therefore, hand-pick the ferrous parts and then collect your dust by regular sweeping. Another way is to loosely wrap a sheet of tissue paper around the magnet. The magnet will attract the platinum dust and all you have to do is to fold the paper around the filings and dispose your catch into your platinum cobalt collecting bin.

Annealing
During common cold working operations, platinum will work-harden to a point that increasing dislocation density makes it necessary to re-crystallize the grain structure. The re-crystallized metal will then allow further rolling-or pulling steps. Although the need for annealing is undisputed, it seems that the determination of the right temperature is the lesser-known fact. The trick is, to heat-up the piece hot enough and to hold that temperature long enough to achieve a proper re-crystallization. Annealing can be done on a welding pad, although you will get more predictable and accurate results using a furnace.

Stress relief
When joining platinum to gold components, use cadmium-free gold solders. Cadmium will cause brittleness because it moves into the grain boundaries. Also, protect the gold portion(s) of the jewelry piece from oxidation during brazing by dabbing a powdered mix (50/50 ratio) of denatured alcohol and boric acid on the gold and let it dry. During brazing, this coating will produce an anti-oxidizing glaze on the gold. When in need of a parting agent for platinum-to-gold or platinum-to-platinum joining, zircon oxide paint (ZrO) is a great brazing-filler-stopper. It will not contaminate the platinum, since it is designed to withstand the heat of high temperature operations.

After the joining process, it will be necessary to stress-relief the assembled piece, especially if it has been extensively locally cold-worked. Because the two metals have very dissimilar shrinkage and expansion properties, cracking will result unless the stress is relieved. Heating the assembled piece in a furnace at 750°C for about 20 minutes with cooling time in the furnace afterwards will achieve the desired effect. During this process it will be necessary to protect the gold portion of the piece from oxidation.

If a furnace is not available in your shop, you can stress-relief the piece with a standard bench torch. This method is less accurate, as its parameters are less controlled, but it will still support your effort to reduce cracking or tearing.

Conclusion:
Platinum is an exciting precious metal that can do wonderful things for you if you take it for what it is. When approached with the proper work ethics and with the right tools, it will allow you to create distinctive jewelry designs that take advantage of its unique attributes.
 

V6N6

Bench Tricks for the Platinum Smith
Kathrin N. Schoenke, President,
Siegfried Becker, USA, Master Gold Smith, G.G.

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