Sunday, April 21, 2013

working with customers platinum

Today I got an email from a talented friend named Sarah Loertscher

 She was looking for some information about working with platinum her email and my response is below....

 I have a quick question for you about platinum - I have a client that wants to reuse her grandmother's rings into small post earrings. I've found that using the rings in a casting situation is prohibitively expensive, because of the contamination and subsequent refining of the extra metal. I was then thinking about melting down the bits of platinum into little lumps, which I would then lightly facet and solder a post onto. Have you ever worked with platinum like this? I know it had an extraordinarily high melting temperature. I have an oxyacetylene torch… I was thinking maybe a rosebud tip would be appropriate. Anyway, any thoughts would be awesome, Just let me know!

   So working with platinum, your torch should be totally fine you just need to make sure that the flame you are using is Oxidizing.... and NO carbon near the metal while you are melting it. Platinum is a serious carbon scavenger so use a clean ceramic block. If you don't have one I have some dead platinum crucibles that have a very pronounced groove on the side that I sometimes use to melt bits of platinum on they are made of "alumina and fused silica.
The other things to pay attention to is alloy type, which is sometimes hard to determine and if there is any solder in the ring you are going to melt.
The most important part is eye protection, I use #10 welders lenses. You can safely go as low as #8's but it will be hard to look at the molten platinum for very long.
Alloy..... does it look like a store bought ring or a custom made ring? Does it have a stamp ( PLAT, Pt 900, Pt 950) and a makers mark? If it has a makers mark that you can find usually you can also find out what alloy they use in their rings. Of all of the alloys a cobalt/platinum alloy is the only one to be overly concerned with, they are great for casting but a not so easy to fabricate or size without a laser welder.
Solder... a lot of times if a ring has been sized or repaired solder is used, sometimes jewelers use white gold solder to repair platinum because of the lower melting temperature. So the trick to finding that out is to heat the ring up with a torch till you get a little glow from the metal (use an oxidizing flame) don't get it too hot. Then let it cool down, if there is any solder it will turn black and the platinum wont. The you can avoid the solder if you know where it is and just don't use it.
As far as your oxyacetylene torch it's hot enough, platinum alloys have an average melting temp of around 3100° F and your torch can run up near 6000° F and is usually considered to be the best for torch work on platinum as long as you keep the carbon down by using an oxidizing flame.  

James M...

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