Things you need to know
This is a more exacting casting process that differs in temperature and precision from traditional casting/finishing.
A. You must plan & sprue for a low flask temperature at casting. See chart below. Use a dark strong wax. A steam dewax process is required due to the fact that true “burnout” temps are never reached.
B. You must exactly match stone size to the wax model being set. Sieve your stones.
C. You need 70% new metal in each cast. This metal needs as low a flow temp as practical. Use our alloy #21ce for best results.
D. You slow cool the flask at least 1 hour to “hand cool” temp., then blast off investment with a pressure washer. Do this in a enclosed cabinet to recover stones that come loose.
E. You must “magnetic tumble” finish instead of stripping/pickling.
F. After casting, wash, & check for missing stones. Then clip items off of tree, grind , tumble finish.
G. This is a proven technique in 10kt & 14kt yellow gold set with diamonds, rubies, sapphires, & cubic zirconia. All others subject to experimentation/frustration.
H. Co-ordinate model making with stone setters. Your models must be adjusted precisly to the stone size. Train your wax people with setters. Apply complete quality inspections to the waxes before investing. All wax flaws will faithfully show up in the casting, every time.
I. Be sure to run a large button to assure orderly freezing of the metal, that is to prevent shrinkage porosity. Sprue with this in mind.
Flask burnout chart… (All flask temps in Fahrenheit!)
Steam dewax first!
200° for 1 hour
250° to 350° ramp 1 hour
350°-450° ramp 1 hour
450°-650° ramp 1 hour
650°-850° ramp 1 hour
Cast at 850°
Gold notes- Use a Karated gold that flows no higher than 950 centigrade. Our #21ce or #34 is a good start for 10kt-14kt. Use the most accurate, fast melt you can. Temp control is essential to this technique. Be sure to run a large button to assure orderly freezing of the metal, that is to prevent shrinkage porosity.
Slow cool flask until you can pick it up by hand, blast off investment in a enclosed cabinet (if you need to recover stones)
Note for Cubic zirconia….. Cast, then place flask back in oven… then shut off heat to oven for a long slow cool down to room temp….