Working with Platinum/Work Space and Tools
INTRODUCTION
Before World War II platinum was the metal of choice for many fine jewelry peices, especially engagement and wedding rings. Platinum was also used to enhance the beauty of diamonds and other precious gems. Many of the world’s greatest diamonds were set in platinum, including the famous Star of Africa in the British Royal Scepter and the beautiful and famous Hope Diamond on display at the Smithsonian Institute in Washington DC. During World World II, platinum was classified as a strategic metal and deemed off limits to jewelry manufacturing, thus losing its market share to the newly developed white gold.
Today platinum is enjoying its renaissance. In the U.S., platinum consumption has risen by over 1500% since 1992. More jewelers are carrying platinum jewelry, and consumers are becoming more aware of the most noble of all metals.
Many jewelers are still turning down platinum repairs because they are not familiar with the metal and fear ruining an expensive piece. For many years, platinum jewelry was rarely brought in for repair, as many pieces were estate jewelry and owners feared irrevocable damage. Platinum's popularity has created the need for trade and consumer education, as more jewelers sell and work with this metal.
WORKING WITH PLATINUM
What does it take to be successful at repairing, customizing and servicing platinum jewelry? First an understanding of properties unique to platinum, and realizing that it is not more difficult to work with, but different than any other metal you may have used in the past. Skilled jewelers should have no difficulty adapting to working with platinum, once they understand the metal’s characteristics.
When platinum is mined, it is usually found along with its 5 sister metals, also called PGM’s (Platinum Group Metals). They are Palladium, Osmium, Rhodium, Ruthenium and Iridium.
As with all precious metals, platinum in its pure state is too soft to be used in jewelry. It must be alloyed with another metal to improve its workability.
The most common alloys in the United States are 95% Platinum with 5% Ruthenium or 95% Platinum with 5% Cobalt, 95% Platinum with 5% Iridium, and 90% Platinum with 10% Iridium.
Platinum has an extremely high melting point (about 1773°C/ 3224°F). This varies somewhat depending on the alloy used. When soldered, brazed or welded, it becomes white hot. This intense white hot radiation contains UV rays that can harm unprotected eyes.
Use #5 gas welding glasses for soldering small jewelry pieces for a short period of time. These goggles are sufficient for most repair work. When welding for longer periods of time, use #6 goggles. But when casting platinum, use #10 or even #11 electric welding goggles. Their filtering lenses also protect against harmful UV radiation generated by the high temperature flames.
Never use sunglasses to protect yourself against the rays and white light. Even the densest of sunglasses offer very little protection against UV radiation.
Traditionally, platinum solders (often also referred to as filler metals) are available from “extra easy 1000” to “extra hard 1400” to “welding 1500”, “special welding 1600”, “seamless 1700” and “plat weld" 1773'”. The number behind each solder corresponds with the approximate flow point in Celsius. These traditional solders contain very little platinum and while they are still being widely used, they have been replaced with a better, high purity solder. These high purity solders, also called “Plumb solders”, come in soft, medium and hard and contain 90%-92.5% and 95% platinum respectively.
Flux is not recommended when using solders over 1300°C/2327°F, as platinum does not oxidize during soldering. This does not apply to Platinum/Cobalt and some specialty alloys, which will oxidize at high temperatures. In these cases, the pieces are being soldered and oxidation is allowed to be removed after the operation.
WORK SPACE AND TOOLS
Cleanliness is essential when working with platinum. Your work bench, tools and the soldering area should be clean and clutter-free. Platinum is very easily contaminated so tolls used for gold or silver should not be used for platinum. Sand paper sticks as well as files should be used exclusively for platinum.
When heating platinum it can be easily contaminated by other metals. Lower temperature metals will melt into platinum. Any jeweler knows what lead can do to gold. Well, to platinum, all other metals is lead, and can be melted into the platinum during high temperature soldering or welding operations. This can make platinum brittle and unworkable. Once contaminated, refining is the only way to reclaim the platinum.
Be careful when using holding devices such as tweezers, binding wire etc. as they can produce a dark stain contamination on platinum that only heavy abrasives can remove. Keep holding devices away from the heat source. Platinum has low heat conductivity, so working with the torch held 1/2 inch away is usually sufficient. Use tungsten tweezers.
Use an alumina or zirconia-based ceramic soldering block for platinum repair work. You’ll also need safety goggles, a tungsten soldering pick, a pair of ceramic tip tweezers, double AA tweezers and a Third Hand. Be sure not to use acetylene or similar fuel, as these type of gases expel carbon in the flame, which contaminates the platinum as it is being absorbed. This will result in brittleness or cracking. Fuels such as hydrogen/oxygen, propane/oxygen or natural gas/oxygen will work very well. Many jewelers are also using water torches which create hydrogen and oxygen. However, it is important to disable the flux inflame feature of the these torches to avoid contaminating platinum with expelled flux. The flame will be pinkish in color rather than green if is safe to sue with platinum.
Platinum solders do not flow over distances. If you need to solder a seam, place many small pieces of solder close together and follow the seam with the flame until it is soldered.
I recommend rolling the solder very thin and then cutting it into small pieces. This way only very small amounts of solder are sued at a time. It is not possible to move solder once it has melted, a new piece must be used.
All joints should fit close together. Solder is not used to fill gaps. A properly soldered joint will look shiny and clean. When soldering platinum, you should not use fire coat or flux. Some jewelers use flux to hold a small piece of solder in place, but at the high temperature being used, the flux burns away and may become a contaminant as it will be absorbed by the platinum. You can use saliva to stick solder into place
This is part one of the series Basic Platinum Repair Techniques written by Jurgen J. Maerz, Director of Techinical Education for Platinum Guild International USA