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Casting Platinum


#1

Was: Why is platinum popular?

But can I cast in it when all I know how to cast is sterling? I get
nervous when my caster tells me it usually takes them a couple of
times to cast Pt right....so how am I supposed to do it? 

Just so Kennedi and everybody knows. 1st - a caster who needs “a
couple of times” to cast platinum should practice on their own work
till they get it right. But…casting platinum is an entirely
different technology from casting silver, bronze or gold. It is
"casting", yes, and casting is casting, but the temperatures and the
tolerances of it all make it very, very different. The learning curve
of jumping from casting silver to casting platinum is probably higher
than that of fabricating the same two metals. It’s tough, and takes
certain equipment - plus it’s high overhead… Not to mention
inherently dangerous.

http://www.donivanandmaggiora.com


#2
But can I cast in it when all I know how to cast is sterling? I
get nervous when my caster tells me it usually takes them a couple
of times to cast Pt right....so how am I supposed to do it? 

You need to find a new Caster (although anybody can have an
occasional miscast). Best Cast in NY does a nice job, so does
Casting House in Chicago. Doing it yourself is tricky at best. You
need high temperature crucibles and investments. Typically you will
want a casting machine that spins at a much higher rpm than what you
will use for gold or silver. You need a hotter melting torch, usually
hydrogen and oxygen. And you must be even more safety conscience
because of the gates-of-hell temperatures the molten platinum much
reach in order to cast properly. So it’s difficult, risky and
requires some equipment investment. We only started doing it
ourselves because we were doing enough platinum that the cost of
shipping and time delays were creating a little trouble for us. When
the platinum price shot up we had so few platinum custom jobs that
we started sending it out again. Really as the number of platinum
custom jobs has dropped, the number of 950 palladium custom jobs has
increased to replace it…and we always send out our palladium
casting (but that’s another story).

Mark


#3
And you must be even more safety conscience because of the
gates-of-hell temperatures the molten platinum 

Just for education in this thread… One of the huge differences
between platinum and all the other precious metals usually used is
the daunting melting point, which many people know either
practically or intellectually. It’s like triple the temperature of
sterling, more than double that of most gold alloys. Another thing
that factors in is the freezing temperature. When you have molten
silver in air you could think of the temperature differential as
being ice water, with molten platinum it’s like liquid nitrogen.
That’s surely confusing, but what it means is that the button of
silver will sit there for a whole minute, maybe, more or less
liquid. A button in platinum freezes the instant the torch is
removed. The ambient air is 4000F cooler than the metal. If you’re
casting in a centrifuge, you also have a hot crucible retaining heat
(quite a sight to see, in platinum!) In a standard centrifuge, you
pull the torch away, drop the pin, and let go of it. Then the
inertia throws the metal through the hole into the flask. Although
platinum has been cast like that by people I know, generally by the
time the metal goes through all that it is frozen… That’s why
platinum machines are verticle - the first motion uses gravity to
drop the metal, along with inertia (and a bigger spring, too). Just
that little extra force and motion can mean the difference…

It’s been said - flying molten platinum will go through most
everything like a laser beam. It makes molten lava look like bath
water. Knowing what one is doing and using safety precautions
becomes real important real fast.

http://www.donivanandmaggiora.com