Hi Mike Here are a few suggestions for you. Platinum is not a
difficult metal to work with but is a little different from gold or
silver.
There are several different types of platinum alloy and each is
designed for different purposes. If you are going to fabricate your
piece by hand you should use platinum iridium. One of the great
advantages about platinum to keep in mind is that you can use much
thinner pieces than with either gold or silver. If the piece you are
constructing is going to be composed of only platinum then most of
your work should be wielded together instead of soldered wherever
possible and where you find it necessary to use platinum solder use
the highest possible (1700). You can make your welding material by
simply rolling out a piece of platinum as thin as possible (the
thinner the better).
Platinum Iridium is a very stable metal and does not react to heat
by developing fire scale like gold and silver do, so you do not need
to use flux when wielding or soldering, but it can be contaminated by
steel when heated so be careful.
Make sure your bench is clean and free from other metal sweeps and
dust such as gold and silver filings or dust and steel filings. One
of the problems encounter with welding platinum is that dirt or metal
dust or filings can cause pitting in the weld seams.
Ideally you should have a set of tools dedicated to only working on
platinum such as a high temperature soldering block, goggles, saw
blades, files and sandpaper. This is because bits of other metal
imbedded in your files or sandpaper or saw blades and such can
contaminate your platinum and make it difficult to get a good finish
on the piece.
When constructing your piece try to be as exacting as possible. The
better your parts fit together before welding them the easier it will
be to get a good finish. You should also finish and polish your parts
before welding them together. One nice thing about platinum is that
heating it has no effect on its finish.
Avoid using steel tweezers to hold your parts together while welding
them. Steel will stain heated platinum. Crazy glue works very well
to hold the parts together.
The hardest part of working with platinum is getting a mirror
finish. When you are ready for the final finish, go over the entire
piece and check for pit holes. If you find pit holes use a cobalt
burnisher to get rid of them. You can also use heavy duty sewing
needles in hard to reach areas. You can then use progressively finer
files and sand paper to smooth out the metal. You could start with a
#2 file and work toward a #6 file, then use progressively finer grits
of sandpaper. you may even want to take a #2 lead pencil and rub a
coating of it over the finest grit sandpaper you are using for the
final sanding. The platinum needs to be sanded to almost a mirror
finish before polishing.
You should use polishing wheels that are dedicated to just working
with platinum and get the polishing compounds that are designed for
working with platinum. There are several good ones on the market.
Most importantly be patient. Finishing platinum is very tedious but
the results make it all worthwhile.
Have fun
Ted Curtis