Problems casting Argendent 62 Porc. to Gold Alloy

[Dougie]

I have been casting for a large lab for over 20 years. We have been using Argendent 62 for our Porc. to gold frames for longer than that. Around 5 years ago, we started to notice foreign objects in our buttons after casting. These objects are small & grey. I have to dig them out with a carbide burr if they don't blast out. They are so hard that if they are large enough, I can dull a brand new carbide burr, which leads me to believe that they are silicon in nature. Sometimes they get lodged in the castings themselves. We had been casting on an induction melt centrifical force casting machine(Austenal ECM4) for most of the last 25 years, using a carbon insert in the crucible. This problem has only started to surface in the last 5 years. The alloy manufacturer led us to believe that it was from using an induction melt casting machine. Others led us to believe that it was a silicon binder in the carbon insert. So my boss had me ditch the induction machine. We have been torch casting the alloy for the last week, starting with brand new metal, and guess what, that stuff is back . It is not investment. We know what that looks like. This stuff is hard and grey. It has happened with both torch and induction, with three different kinds of investments. This problem does not happen with any of the other 12 alloys that we use. Does anyone have a clue to what this might be?
Thanks,
Dougie

[Zzzdentist]

Sadly enough the dental lab chat portion of this forum hasn't been as busy as I hoped it would be even though wow we're listed as third under a Google search for "dental lab forum." In the interests of you finding a more timely solution and input, I might suggest that you try posting your question over at http://www.dentaltown.com or another lab chat site.

I was going to refer you over to dentalab.us, but it looks like they aren't around anymore. Geez, when I do a Google search for "dental lab chat" we're listed a number one. Gulp! Sorry, there just aren't many lab people that I have bumped into on Dentalminds. I was hoping for more participation, but it just hasn't gotten that much of a response from other people in the dental field.