Platinum Casting in a Small Shop

1. Due to the huge increase in customer demand for platinum jewelry, more and more small shops are needing to add platinum jewelry design and manufacture to their in-house services in order to stay viable. Completing jobs on time and under budget with minimal expense and with the least amount of down time has always been a hurdle for the smaller shops. Adding platinum production comes with its own set of additional hurdles…or so I was led to believe.

As I began to research platinum in my own shop, I was initially daunted by all of the conflicting information out there. I’d heard platinum was hard to work with, that I’d need to purchase specialized and more expensive equipment. I wondered whether I could work with platinum in-house and still turn out a quality product that met my high standards.

2. In the end, weeding through the mounds of conflicting information proved to be the most daunting part of my investigation. The biggest misperception about platinum is that it is difficult to work with. Platinum is not a difficult metal to work with, it just has different properties than other metals. It’s very dense making it difficult to polish (some say) or flow in casting. It melts at extremely high temperatures, and it solidifies extremely quick. Once platinum’s unique properties are properly understood and allowed for, many find that working in platinum is actually easier than other metals. And most important for any size shop, while platinum is an expensive metal, it is also a forgiving metal. Unlike gold alloys, if your casting fails, the platinum can be re-cast over and over again.

I believe that every goldsmith can learn to work with platinum. I hope that this paper will dispel many of the misperceptions surrounding platinum and encourage everyone to take up the torch. 3. Misperception #1: Specialized Equipment is Needed

Because of platinum’s unique properties many assume that they will need to buy special equipment to cast with it. This is only minimally true. I discovered that many of the tools I already had in my own shop were more than sufficient for casting platinum.

Through practice and much experimentation on my own and with the encouragement and support of the Platinum Guild and the Revere Academy of Jewelry Arts I was able to perfect a number of methodologies and uncovered a valuable time-saving investment product which I will share later in this paper.

3. Casting Machines

The vertical, horizontal and the induction casting machine models are all acceptable for casting platinum. For most small shops the induction casting machine is irrelevant due to its high price tag ($30,000), so I will not spend time addressing it here, nor have I done much experimentation with it. 4. I use a Neycraft horizontal centrifugal spin caster in my shop. I like a horizontal centrifugal caster better than the vertical centrifugal casters, because it has a rotating drum. The drum is preferred for several reasons: it protects the caster from metal flashing out of the caster and possibly hitting him and thus prevents metal loss which is expensive; it is easier to control in comparison with the vertical caster and most small shops are already outfitted and used to this type of casting machine. My Neycraft casting machine has held up for at least a 600 platinum castings to date,and I see no end in site.

4. Crucibles

There are special crucibles on the market designed to withstand the high temperatures (3250 degrees Fahrenheit) required to melt platinum without breaking down as readily as crucibles designed for other metals. They will break down eventually and should be replaced more frequently than crucibles used for gold. The standard platinum casting crucible is the large Wesgo A type fused alumina crucible from Rio Grande. A GAAB crucible holder can be purchased for the Neycraft to hold a large Wesgo A, however the Neycraft casting machine already comes with high temperature casting crucibles which seem to work just fine.

5. Misperception #2: Platinum is Difficult To Cast

Platinum¹s density is what gives it its satisfying weight, but what also makes it flow less easily and solidify very quickly. In casting this poses problems that are easily overcome by preparing waxes properly. As with other metals the correct placement of sprues is critical to making a successful casting.

6. Preparing Waxes

As with other metals, before investing check waxes for problems: make sure that the piece being cast has an even wax thickness throughout the piece to ensure correct solidification (cooling down) of the metal. If the wax is uneven the platinum will cool at an uneven rate creating shrinkage porosity. Check for imperfections, smooth surfaces and for the placement of sprues or gates. Larger gates are required for platinum than for gold, and the use of extra gates are strongly recommended as platinum solidifies in approximately 3 seconds. The larger gates enable the molten platinum to reach its destination more quickly and feed the piece during solidification. Hoover & Strong Precious Metals West Kerr HOME Preparations Conclusion | 800-759-9997 | (fax) 800-616-9997