The March 2015 edition of From the Bench was dedicated to casting in all its complexity. In this latest publication, you’ll find articles on the evolution of casting, mold making, hand tools, and even an interview with our in-house casting expert, Dennis Busby. But we aren’t leaving you with just that. No way! Read further for more tips and answers to your frequently asked casting questions from Dennis Busby himself.
Q. What’s the proper or best way to solder a platinum head to gold? Should you flux the platinum component when using gold solder?
A. Yes, always use a fire coat and flux when soldering any metal; this keeps the gold from oxidizing. And, yes, you want to use a gold solder when assembling platinum head to gold.
Q. How do you figure out resin weight to metal weight?
A. There are slight differences in the weight of wax, plastics, and various resins. We do not differentiate between any of these at Stuller because it’s so close. The difference between different colored waxes is negligible. You can find some very good specific gravity calculations on page 18 of Stuller’s 2009 Metal’s Catalog.
Example: (wax or resin weight) x (specific gravity of metal required) + (button)
Q. What the best non-toxic compound to use to divest platinum investment?
A. There’s really no such thing. Caustic solutions are safer than alternative acid.
Q. When casting palladium, how do I get rid of plaster residue?
A. As with platinum, your best bet is a caustic solution. Sand blasters with glass beads can certainly speed up the final clean.
Q. What’s the best way to remove pit marks from castings?
A. Well, at Stuller, we use the Rofin Laser Welders for filling pits. You can also burnish the area down with margin roller
burnishers.
Q. How does Ferro Vest impact platinum casting?
A. Two-part platinum investments (binder + powder) like Ferro Vest produce smoother surfaces than the phosphate-bonded-just-add-water-high-temp investments.
Q. Can you do resins in two-part platinum investments?
A. No, if you’re going to direct cast a resin without molding it, you will need to add a dental investment formula to your bag of tricks.
Want even more tricks of the trade? Click here for a list of defects and possible causes.