Platinum in its finished state is an absolutely beautiful metal. It can also be a little tricky when working it due to the softness of the metal. Knowing what tools and techniques to use can make the job a whole lot easier.
Here are a few things you need to know about working with platinum.
First Thing’s First
The first step is knowing which platinum alloy you are working with. Platinum/cobalt,
platinum/ruthenium, or platinum/iridium. Each alloy has its advantages and disadvantages. Platinum can be a soft metal as far as finishing goes, platinum/iridium being the softest of the 3 mentioned above. Platinum/cobalt is the hardest of the three as cast.
If you’re not sure of the platinum alloy there are a couple of ways to check, one being the stamp. Platinum/cobalt and platinum/ruthenium may be stamped just PLAT, or Pt950, whereas platinum/iridium should be stamped Pt900. Of the cobalt and ruthenium a simple magnet can distinguish between the 2. Cobalt is slightly magnetic. Use a magnet to tell if a ring is made of a platinum/cobalt alloy.
Choose Your Tools Wisely
It’s important to have the right tools – burnishers, platinum sand paper in several grits, rubber wheels, and ceramic stones ext. A list of tools is at the end of the article. It is also a good idea to keep a separate set of tools just for platinum to prevent contamination, and make polishing the platinum easier. Another tip to a beautifully polished piece is to make sure to pre-clean the grit from the piece after prepping, leaving the dirt and grit on the piece can transfer to the buff making it difficult to get the high polish results without a scratchy looking haze on the piece.
Let’s Get Started
If you have a vibratory tumbler with stainless steel shot (pins, balls, and diagonal Stainless steel shot) tumble the piece for at least 20 minutes. This will shine up the areas that are hard to reach as well as work hardening the metal, making finishing the platinum a little easier to work with. If you don’t have a tumble, you can burnish the piece using a flex shaft and a tungsten-carbide burnisher or by hand using a hand burnisher. Burnishing the piece will save time when removing the scratches from the prepping process.
Round out the piece first to make sure you don’t end up with flat spots when you removethe sprue. Sand the inside with a sanding cartridge. The coarser the sand paper, the harder it will be to remove the scratches (keep that in mind). Remove the sprue, using a diamond wheel or belt sander, again the coarser the tool the harder it is to remove the scratches. Use a deburring wheel or a buff stick to smooth the surface, and remove any rough scratches. By using several grits, and stepping up the grit will make polishing that much easier.
Now that the shank is prepped, let’s get started on the head area. Remove all unwanted surfaces on the head using a rubber wheel and/or bullet rubber wheel in the areas that are easy to get to without changing the shape of the prongs or the bearing. You may have some rough texture that you’ll need to work with a ceramic stone. I use an ultrasonic polisher for this, but if that’s not an option you can use a pin vise to hold the ceramic stone. Once you have removed all the rough surface with the ceramic stone go over that area with radial bristles, start with the red radial bristle than go to the blue radial bristle. This will make head polishing a lot quicker.
Now, let’s work the gallery. Thrumming in the gallery can create a high polish just as beautiful as the rest of the piece. For this, you can use precut slurry sheets in different grits or a platinum sand paper in the different grits (make sure to cut the strips to fit the gallery opening).
Time to Polish
Let’s start polishing! You’ll polish the head area first using a soft mm, geza brush, or end brush and the luxor red polish. The luxor red is an aggressive polish, so you want to be careful not to over polish. Then you will polish the inside, using an inside felt polisher and the luxor red. Polish all scratches out (if you’ve taken the necessary steps with the sand paper cartridges this should go quick). Then you will polish the outside of the shank with a hard buff using a firm stitched buff and the luxor red, then follow with the Avivor polish. Lap the sides of the shank with a lap machine or a knife edge felt wheel (this looks like a felt rubber wheel) using a flex shaft and the luxor red again. Now let’s final buff. For this you will need a soft muslin buff and Avivor or Oras polishing compound. Polish the entire piece until all scratches have been removed. Make sure to work the head, sides and shank to a high polish.
Use safety precautions to protect your eyes, by using a #5 or #6 rated welding safety glasses should keep you safe from damaging your eyes while soldering on platinum. When soldering platinum it is very important not to contaminate the platinum. Always make sure the piece is clean of any oils, dirt and polish before soldering, and by keeping separate tools used solely for platinum (solder pads, ceramic tweezers, tungsten picks, etc).
It’s also important to note that it is not recommended to use boric acid mixture or flux when soldering platinum. For assembling a head to a shank a 1500 C repair solder is recommended, soldering a peg head to a shank or an earring post to an earring a 1200 C repair solder is recommended, for sizing a 1700C solder has the best color match and there is less of a chance of solder erosion. Use natural gas/oxygen, propane gas/oxygen or hydrogen/oxygen when soldering platinum. When using a water torch make sure to disable the water feature on the torch. Do not use Acetylene gas when soldering platinum, it’s the dirtiest of all the gases and full of contaminants. Now that you have soldered your piece finish the platinum with the steps from above.
Do you have any tips for working with platinum? Tell us in the comments section below.