Has anyone had much success with casting palladium white gold? I
have tried normal vacuum assist casing and had very little luck.
Usually I end up with incomplete areas where no flow is apparent
even with increasing metal temperature and flask temperature. Any
help out there? Could the problem be the method of casting or the
equipment?
Ron Kreml
Ron,
Palladium white gold is not as fluid as most gold alloys. However, I
have had good success with centrifugal casting these palladium
alloys. Also, we are using a pressure over vacuum machine currently
and getting excellent results. The major problem that I have faced
besides non-fill has been a reaction between the ceramic crucible and
zinc under vacuum melt. This reaction produces “wilemite”, which
appears as a dark slag or dross on the melt and can lead to
inclusions in the subsequent castings. For this reason we cast with
zinc free palladium white alloy for 18K and a low zinc (1.5%) for
14K. These alloys do not require special investments or crucibles
(can be melted in a graphite crucible).
Chris
Hi Ron, I have been casting Palladium white gold for over ten years.
I encountered some problems at first with non fill as well. I cast
centrifugally and use a high temp investment (same as for platinum)
This investment allows higher flask temps before it breaks down. You
can cast with the flask glowing and not overheat the metal. One of my
first problems casting the Palladium gold alloys was conventional
investment binding to the casting when the flask was hot enough for
the pattern to fill. Generally, I find that vac casting requires
slightly higher flask temps to achieve a good fill. I do use both
methods but save vac for very large items invested in big cans. I
don’t want to resurrect the centrifugal/vac debate. Please check the
achieves for all the lively discussion on the topic.
Hope it helps.,
John, J.A.Henkel Co., Inc. Moldmaking Casting Finishing, Producing
Solutions for Jewelry Artists
Hello Ron: It is possible that the filter on your vacuum caster is
plugged and you are basically gravity casting. Your gauge will show
that you have good vacuum but it is only up to the filter. Test it by
turning on the vacuum caster and seeing if it is pulling by putting
your finger over the hole. You can get new filters from just about
anywhere even auto part stores. Hope this helps
Michael R. Mathews Sr. Victoria,Texas USA
Hi Ron;
Check the melting temperature of the metal you are using. Palladium
white alloys usually melt at around 250 degrees higher than nickel
white. Your mold needs to be appropriately hotter when you pour and
don’t scrimp on the sprue system. The metal needs to get in there
quick, so keep them heavy. I also often use several smaller sprues
going to the farthest parts of the casting so that the metal doesn’t
have to pass through any narrow gates before getting to the extent of
the cavity.
Also, I hope you are using a non-crystobolite investment. Palladium
doesn’t like the sulfer in conventional investment, besides the fact
that conventional investment isn’t designed for those higher
temperatures. Also, melting with an electromelt is not advised. Too
much carbon present. When melting with a torch, keep the flame ever
so oxidizing.
David L. Huffman
I have been using the pallladium white gold for a couple of years I
have never been able to vacume cast it but I have been very
succesfull using my centrifigal caster it is a vertical platinum
machine. I have used both types of investment, platinum and regular
kerr satin cast and have had no problems with either. I use the
regular type now because I could tell no difference. I cast the
flasks a little hotter though just to be sure it fills. I really like
the palladium white gold alloys they are nice to set in and stay very
white.
Kevin Potter