Dear Patty in Missouri,
I’m not quite sure what you mean by “semi-mounts”, but I do use a
lot of platinum in conjunction with other gold alloys. In
Australia, we use mostly pure platinum or a 5% copper-platinum
alloy which is a little harder than the pure. As you probably
already know, we don’t normally make in 14ct - in Oz it’s usually
9ct and 18ct. However there is an increasing amount of 14ct
mass-produced stuff coming in from Asia.
When I’m soldering platinum to 18ct yellow gold, I have found that
18ct medium yellow gold solder seems to make for a trouble free
and secure join. I prefer to presolder by melting the medium solder
onto the platinum first, then place it in position on the 18ct
yellow gold component and literally pull it down onto the gold by
favouring the gold with the most heat as I’m soldering.
I use a flux called Auflux. I don’t know if you have this in the
’States; it’s a greenish coloured liquid.
I don’t like using platinum on any lesser quality than 18ct,
because the extra alloy in lower carat golds seems to create more
oxidisation which may cause problems in the solder join.
As for polishing, I carefully buff off file marks with a 1200 grit
emery paper stick, then brush with brown tripoli, then brush and
buff with green rouge, then finally brush and buff with red rouge.
It almost goes without saying that I have separate brushes and
buffs for each compound, cleaning the piece between each subsequent
polishing stage, then finishing with a very soft lambswool buff for
my red rouge.
I hope this helps. It’s helped me for the past forty years.
Regards, Rex from Oz.