GEM SET WAX PATTERNS SHOULD BE CAREFULLY INSPECTED before assembling trees. The alignment and fit of gemstones may need a slight adjustment before committing to casting. Check the table height on the gems and make any needed adjustments with a heated wax pen. It is much easier to make adjustments in the waxes than it is after casting in metal.
WAX PATTERNS SHOULD BE MOUNTED ON A TREE rather than on a sprue base. The size of the tree is dependent on the burn out, flask temperature used and the casting procedure used. For Vacuum casting a 6" flask can be used for the lower temperature method and up to a 10" flask can be used with the higher flask temperatures possible with the special gemstone casting investments. For Centrifugal casting a standard size flask can be used for both higher and lower flask temperatures. Be sure to leave a one inch space between the sprue base and the first row of waxes, this will avoid the main shrinkage area on the tree.
INVESTING IS DONE ACCORDING TO THE MANUFACTURERS INSTRUCTIONS. If you are using the special gemstone casting investment be sure to read and follow the recommended investing procedures.
Mixing instructions may differ between investment manufacturers.
MAKE SURE THE INVESTED FLASKS HAVE SUFFICENT VACUUM TIME to get rid of air bubbles.
Any air bubbles trapped under or near the stone set areas will create metal nodules in the castings that are difficult to remove. A very small amount of liquid dishwashing detergent added to the water used for investing will aid the wetting properties of the investment to prevent trapped air bubbles.
ALLOW INVESTED FLASKS TO SET FOR 1 TO 1 ½ HOURS. If steam de-waxing is used allow a 2 hour set up time before beginning the de-waxing cycle. Inadequate set up time can cause investment breakdown during the steam de-waxing process from hydration of partially set investment.
STEAM DE-WAXING IS HELPFUL for gemstone set in wax casting. Due to the somewhat lower burn out temperatures used in this process, steam de-waxing is helpful in removing wax from the invested flasks.