Q: I want to make some jewelry out of platinum. Is there anything special I need to do?

A: To work with platinum, the following rules and observations may be of
help:

1.The flame must always be at least a little oxidizing. As you might already know,
carbon contaminates platinum easily, causing brittleness. An oxy-acetylene torch
will cause problems due to its dirty flame.

2. Use an ultrasonic or steam cleaner on all parts immediately before
any soldering or annealing, to be sure they are clean and free of any
grease or fingerprints, etc, which can be a source of carbon upon
heating.

3. If you are holding the piece(s) using steel tweezers, be sure that
they are well away from the areas you are actually heating. If the
steel gets anywhere near the platinum soldering or fusing temps, it can
contaminate the platinum. It's possible to use such tools, but you must
be careful. Fortunately, platinum doesn't transmit heat well from one
section to another, so if your flame isn't larger than needed, and is
pointed away from the tweezers, you can avoid problems.

4. No carbon sources of any kind should be in contact with the platinum during
heating. That means dirt, charcoal soldering blocks, etc.

5. Take extreme caution to avoid particles (filings) of gold or silver on
your platinum while working with it at platinum soldering temps. At
those temps they will burn holes in the platinum just like lead would in
soldering silver or gold.

6. You can use Batterns or other fluxes to help hold solder paillons in
place while soldering, but it isn't needed. However, when soldering-in
or fusing-in gold inlay, flux is needed to protect the gold.

7. Tungsten carbide makes a wonderful burnisher, which will more easily polish
small details than any other tool, and won't contaminate the platinum.
A thin carbide rod makes a safe soldering poker for platinum as well.
Pure tungsten is the only other metal you can make a really safe soldering
poker with. Titanium won't contaminate the platinum, but at those
temps, it burns. Steel will contaminate the platinum badly.

8. Use either a Wesgo type soldering block (or one of their round
melting crucibles, turned upside down, which is much cheaper than the
actual blocks) or get one of Rio Grande's platinum soldering blocks,
which are much cheaper. They are in essence a high temp fine-grained
fire brick, and softer than the fused silica Wesgo blocks, but work very
well and for much less money. Forget the various other fused silica
"high temp" soldering blocks others carry. Most of the ones I've
tried are jokes. They seem to be too highly sintered, and transmit way
too much heat. Soldering on one set on your bench pin quickly sets the
pin on fire. And the idiots who designed at least one of the available
blocks saw fit to glue on nice looking rubber feet to the underside.
Guess what happens to those rubber feet the first time even a little
heat hits the top of that block? Remember the line in Star Wars, where
Luke, Chewy, Han, and the princess jump into a trash dump and the
princess accuses Luke of discovering a wonderful new smell? Get the
picture?

9. Small ingots can be cast by melting platinum into an appropriately
carved depression in the Wesgo or Rio soldering blocks. Wear a dust
mask, and use a Mizzy wheel or a diamond grinding wheel to carve the
depression. Don't try to cast one with a standard ingot mold; the iron
will trash the platinum. Usually, you're only making a big enough
ingot for a small section of stock anyway, so this is an easy and
convenient, if less elegant-looking, way to do it. You'll find as
well that the stuff rolls out so beautifully that you can successfully
convert even rather rough and ugly lumps into good quality sheet and
wire, where gold or silver in those shapes would often crack up before
the rolls trued up the lumps. You may find when you melt the
platinum onto that depression on the block that the block is melting as
well, and the platinum will seem firmly fused to the block as it cools.
Not to worry. Just let it cool all the way, and by the time it's cold,
it will have sprung loose again from the silica, due to differing
thermal contraction rates.

10. Get a pair of good cobalt blue glasses for melting or soldering
platinum. Rio sells em for a whopping 40 bucks, but if you call the
Fend-all company, 5 E. College Drive, Arlington Heights, IL 60004, at
(847) 577-7400 (I think that's it, or get the number from directory
assistance), you can get the name of a local distributor of their safety
glasses. Fend-all makes the glasses Rio sells, but doesn't sell
direct. The last pair I got from their distributor here charged me $28
a pair. The same company also makes a wonderful didymium-lensed safety
glass. Unlike the intensely dark blue cobalt, good for very high temps,
the didymium lens is only a very light blue color, and changes
your working view very little. But it almost completely blocks a very narrow
band in the yellow, right where the sodium line is, which means that the
bright yellow flare you get when a flame hits fluxes or glass containing
sodium (borax, etc.) is completely blocked. Ordinary glowing yellow
from heat is still visible, but your metal isn't obscured by the yellow
coloration the flame gets from hitting sodium-containing materials.
Glass workers routinely use these glasses, and I've found them very
useful for many delicate soldering or gold and silver melting operations
where a true dark glass isn't really required. They cost more than the
cobalt, like closer to $35 or $40, but are, in my opinion, very well worth
the cost. Once you try them, you'll wonder how you managed without...

11. Work tight. Use as little solder as needed to do the job.
Platinum solder is not actually made with platinum usually, but is an
alloy of palladium and silver, except for the highest melting grades.
So it's no surprise that it's slightly greyer and softer than platinum
itself. If you use too much instead of getting seams tight in the first
place, you'll see the lines and color difference after polishing. For
initial seams, especially in larger chunks, like the seam in a plain
band, you can simply weld the stuff, with no solder at all. Cut the
seam with a side cutter or file a notch, so it's not a seam, but a V-
shaped groove, Place a chunk of extra platinum on top, and heat just
that chunk. It will heat and melt before the rest, and slump in quite
nicely. Just pull back before you then melt the rest of the
piece. Now forge it out a bit and file to shape, and voila- a seamless
joint.

For a neater seam, say in an already made engagement ring's
shank, which you're sizing, don't make it such a wide V, just a slightly
sloppy seam. Roll out a very thin piece of platinum sheet, a little
bigger than the seam, insert it, so it sticks out about a mm. in all
directions. Concentrate your sharp hissing flame just on that little
insert until it fuses into the rest of the shank. Practice this on
scrap stock before doing it for real, to get the feel of it. You may
have to fuse first one side, then the other. Just make sure that your
fusion is going all the way through the seam, rather than lingering at the
outer surface. The big advantage to all this is that then you have no
solder seam to "pull out" in polishing, or to be weaker than the rest of
the shank. Of course, you cannot do this right next to diamonds. But
you certainly can do it to the shank bottom, on a ring with diamonds at
the top. With care, the top of the ring won't exceed the temperatures
that are safe for diamonds. (And as always, be sure that the diamonds
are not treated or otherwise at risk from normal heating, or heat-sink
the stones before doing this.)

12. Depending on the alloy of gold you're using, and the design of the
piece, some gold inlays don't have to be soldered to the platinum.
Instead, heat up the platinum till the gold melts into it, just like
solder would have. The platinum won't melt. Then file off the excess
gold.

13. High karat fairly soft gold (like 18 or 22K) alloys work better in
two tone designs than lower karat golds. Platinum and gold have
different rates of thermal expansion, and harder gold alloys, especially
if soldered to the platinum with softer less strong solders, may tend
to crack away again on cooling, or later, as the differing rates of
thermal expansion/contraction create stresses in the joint. The softer,
high karat golds will simply stretch or compress to accomodate the
platinum's dimensions...

14. Polish any platinum parts and findings and elements of the design
before you assemble them. Heating won't damage the bright polish, so
soldering doesn't disturb the polish except where the solder has flowed.
This means under galleries and the like will need little work to finish
up after assembly if you're careful. And given the greater difficulty
of polishing platinum in any case, anything you can do to make that job
easier is worth doing.

15. Properly emerying out a surface to fairly fine grades of emery, like
400 or 600 or finer, will greatly speed and improve the polishing
process.

16. My favorite platinum polishing compounds are the aluminum oxide
compounds from Gesswein. You use their 800 grit the same as you'd use
tripoli for gold or silver, then the 1200 or 1500 as a prepolish, and
then either their 8000 as a final polish, or their "carrot" compound which
leaves a slightly darker, higher colored polish.

These compounds have the advantage of being hard enough to cut platinum
fairly quickly, so it's possible to minimize undercutting of solders or gold
inlays, if you've carefully prefinished the surfaces with very fine
emery paper first. A drawback is that these compounds are quite a bit
more costly than most polishing compounds we normally use.

17. For just plain polishing of platinum without inlays or solders to
undercut, you'll find ordinary bobbing compound, especially on a brush,
to be useful and fairly fast-cutting.

18. And last, though I've said it already, work clean and carefully.
Many problems people have with platinum come from trying shortcuts or
being sloppy with seams, cleanliness or other parts of the process. The metal is
capable of many things you cannot hope to do in other metals, but it is
also less forgiving of carelessness.

Peter Rowe