WORKING WITH PLATINUM
What does it take to be successful at repairing, cus¬tomizing 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 under¬stand the metal's characteristics.  

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. When soldered, brazed or welded, it becomes white hot. This intense white hot radiation contains UV rays that can harm unprotected eyes.

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 respec¬tively.

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 tem¬peratures. In these cases, the pieces are being soldered and oxidation is allowed to be removed after the oper¬ation. 

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 conta¬minated so tools 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. Be careful when using holding devices such as tweez¬ers, binding wire etc. as they can produce a dark stain contamination on platinum that only heavy abrasives can remove.

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 conta¬minates the platinum as it is being absorbed. This will result in brittleness or cracking. Fuels such as hydro-gen/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 these torches to avoid contaminating platinum with expelled flux. The flame will be pinkish in color rather than green if it is safe to use with platinum.

Platinum solders do not flow over distances. If you need to solder a seam, place many small pieces of sol¬der close together and follow the seam with the flame until it is soldered. I recommend rolling the solder very thin and then cut¬ting it into small pieces. This way, only very small amounts of solder are used 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. S solder is not used to fill gaps. A properly soldered joint will look shiny and clean.

REPAIR TECHNIQUES 
Ring Sizing
There are two ways to size a platinum ring using a torch. One is using the soldering technique, the other using the welding technique. Let's begin with the sol¬dering technique.

I do not recommend using lower temperature, tradi¬tional solders for sizing rings. Plumb solders polish flat and do not turn dark. Usually the welding technique is preferred over soldering, as it makes a seamless connection, which solder does not.

To make a ring one size smaller, remove 2.52 mm of the shank. Scribe the distance onto the shank and remove the metal with a jeweler's saw. Gently bend the shank together closing the gap. Cut through the seam one more time; this aligns both sides and guaran¬tees a tight seam.

Roll a small piece of platinum hard solder until it is about .25 mm thick. If a rolling mill is not available, just hammer a small piece flat using a bench block. Wedge that small thin piece into the cut allowing the tension of the shank to hold it in place. The solder piece should not be larger then the cross section of the ring so that no solder spills on top of the ring during the operation. Grab the ring away from the seam with the Third Hand and solder the shank (use appropriate eye protection). You are finished as soon as the solder has flown. At this point examine the seam to see that it is filled all the way around. You may have to re-solder if it is not. This creates a complete metallurgical bond.
Once the ring has been soldered, round it gently on a mandrel using a mallet. There should be as little dam¬age to the shank as possible. A mallet will prevent hammer marks on the ring. Use a polished burnisher and rub over the seam, making it invisible. Sleight very fine sanding and polishing will finish the sizing.

To enlarge a ring one size, repeat the above technique, except add 2.52 mm of sizing stock.

Sizing with the welding technique is a straight forward operation. Once the shank has been cut, it is not nec¬essary to close it without a gap or cut through again. A small gap or groove filed around the cut is beneficial. I usually hammer the piece removed for a down sizing flat and use it as fuel. This technique makes sure that the alloys match. Wedge the small piece of the same platinum alloy the ring is made of into the cut. Using a sharp oxidizing flame melt the piece into the gap fol¬lowing it all the way around the seam. This creates a seamless bond. After welding, file the excess platinum from the inside of the shank so that it can be rounded on a mandrel. It is also good practice to make the ring slightly smaller than needed. Hammering it to round it will stretch it to the desired size and work - harden the shank for easier finishing.

Platinum / Cobalt Alloy
The introduction of 95/5 Platinum Cobalt Alloy has caused some dialog in the industry and raised some questions about just how to handle this metal. As you may or may not know, Pt/Co is slightly magnetic. It requires care, as many jewelers use a mag¬net to separate broken saw blades from filling in the working tray and that is not feasible when dealing with Pt/Co as it will be picked up with that magnet as well.

When welding or soldering with a torch, the cobalt tends to slightly oxidize. This oxidation is sometimes so minor that it can be removed with a wipe of the finger, or, if it is more pronounced can be easily be removed by fire-coating the ring after the welding job has been completed. Then reheating it to a red and pickling. The cobalt does not oxidize until it is heated to over 1000°C. So in everyday wear, there is no reason to be concerned.

On the positive side, this great alloy allows for beauti¬ful castings, as it has a much finer grain and is more "wet" and thus ideal for casting applications.

Annealing
Before reducing the thickness of platinum sheet or wire in a rolling mill, make sure the rollers are clean. Never reduce plat¬inum more than 70% without annealing.

Before annealing platinum, be sure the surface of the metal is clean. Relieve stress build-up from cold working platinum by heating the piece to about 600°C/1100°F. Softening requires about 1000°C/1830°F. To anneal, heat the platinum to a bright orange ( about 1000°C/1830°F) and hold it there.

It takes about one minute to anneal a 1 mm thick, 25 mm square piece of platinum stock. Quench or air-cool the piece. When picking it up with regular tweezers, wait until it is no longer red hot to prevent staining.   

Re-tipping
Re-tipping is usually defined as "to rebuild a prong tip with the stone in place". This definition limits the job as only a few stones can take the heat needed to place a new tip onto a prong. Retipping a platinum prong with platinum solder will damage any stone. Here is a bench trick I highly recommend.

File the remainder of the platinum prong flat and melt a small amount of easy white gold solder on the tip. Carefully file it flat again leaving a thin layer of solder covering the top. Now place a piece of platinum wire on the tip and connect it by flowing the solder. Cut off excess wire, shape the new platinum tip and polish.

This technique guarantees a platinum re-tip. The soldering will not harm the stone (Diamonds, Rubies, Sapphires). 

Setting Stones
Platinum has the distinction of being called a "dead" metal. This means it has very little or no memory. When a platinum prong is pushed into place, it usually stays without sag or spring .

Platinum also tends to load up on drills and burrs; therefore some care must be taken. Use only sharp, well lubricated drills. Drill a small pilot hole then enlarge it. When using a burr, make sure it is either new or well cleaned. 

Use well polished gravers for pave, bead and bright settings. I recommend Tungsten Carbide gravers as they hold the polish and the sharpened edge best.

When setting a stone into a platinum bezel, make a bright cut along the inside edge of the bezel after the seat has been made. (When burnishing or hammering the bezel around the stone, the edge will be close to the stone. When the bezel is receiving its final bright cut, that edge will appear to be extended all the way down.)

Platinum burnishes well. Use a highly polished tung¬sten burnisher. Be careful as it will immediately drag over a polished surface if there is any debris left on the surface.

As a general rule, polish as much as you can prior to setting or assembly. Platinum does not oxidize so the finish will not deteriorate during those steps. 

Chain Repair
Repairing platinum chain is more simple than repairing gold chain. The high melting point of platinum makes it possible to solder even the finest wires without melt down.

Remember when repairing chain, make sure the chain is totally clean, as body oils, perfumes, and hair will burn onto the metal. Measure and note the distance from the lock. Inspect the clasp and make recommen¬dations as needed.
Use a low temperature platinum solder such as 1200 for chain repair. Do all polishing with a small silicon wheel and only polish the repair. Never polish any chain on a regular polishing motor unless it is properly mounted for safety.

FINISHING
After sizing and setting, you are ready to finish the ring. When platinum is polished properly, it will take on a shine that no other metal can produce. Platinum does not oxidize nor is it affected by atmospheric con¬ditions. This assures a good finish is long lasting. But it takes some effort to achieve maximum results. If plat¬inum is being joined to gold, it is important to finish the platinum section first. Failure to do so will result in over-polishing the gold portion of the piece. Before polishing, all scratches will need to be removed. If you don't do this, you will have polished scratches as it is difficult to remove them through buffing.

SUMMARY
As platinum jewelry continues to gain market share, nearly every jeweler will have contact with this most precious metal. Education and information about plat¬inum is good business. With minor modifications to a workspace and just a few new tools to be used exclu¬sively for platinum, any small workshop can perform most routine repairs on platinum. There is no need to fear working with platinum. After all, it is not difficult; just different. 

V11N7

Basic Platinum Repair Techniques
Jurgen J. Maerz
PLATINUM GUILD INTERNATIONAL

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