I’m sure that I will not be the only one answering your thread. I cast my
JA certification ring two weeks ago in platinum and it turned out great. I
hope Jergen will also coment on this thread.
I used propane and oxygen for my fuel with oxygen pressure at 40 lbs and
propane at 5 lbs. Both valves on the torch control the flame. The oxygen
valve was totally wide open and the the propane valve controling the
flame was almost wide open. This gives you the oxydizing flame necessary
for the melt.
My metal of choice is 90 / 10 platinum irridium for torch melting.
I use the casting machine that spins like a ferris wheel with the tension
spring wound as strong as you can.
It sounds like you over heated your metal. It should spin and be moved by
the flame of your torch. It shoud not be blown out of the melting
crucible. It looks like a ball of mercury when molten. The torch just
chases it around the melting dish.
Your melting crucible needs to be a Wesco quartz melting dish. The dish
itself melts and contaminates the platinum about 200 degrees hotter than
the melting temperature of molten platinum. So the liquid window of your
melt is temperature critical. This means if you overheat your metal you
melt the crucible into the metal as a serious contaminent. This will leave
your casting totally brittle and will crack if you breath on it.
The only torch I have used is a genuine platinum melting torch sold in
most catalogs. Kind of like holding a rocket ship engine in your hand as
you melt. I have not used hydrogen / oxygen.
Platinum cobalt will probably not work with the torch melt. It needs the
argon atmosphere to prevent a lot of carbon related problems.
I don’t claim a lot of expertise here, but I have cast platinum
successfully. I guess I do it for the challenge.
TR the Teacher & Student