I can't remove bits of rubber stuck behind
stones after mold-making.
If pieces of Castaldo® jewelry molding rubber become stuck behind stones in a metal model, the following techniques can be used to remove them.
First, try to dislodge the rubber with tweezers, a pick or similar tool. If that does not work, immersing the piece in warm soapy water in an ultrasonic cleaner may help.
If the rubber still cannot be released, consider the following techniques, depending on the type of rubber involved and the heat resistance of any gem stones that may be present.
For our natural rubber products — Castaldo White Label®, Gold Label® and No Shrink Pink® — use a torch adjusted for a relatively cool flame of about 500° or 600° F ( 260° – 315° C) and heat the area until the rubber becomes a brown liquid. This liquid can be easily dissolved with common solvents such as mineral spirits, acetone, etc.
If the flame is kept on the rubber longer or if temperatures are increased to 800° or 900°F ( 425°- 500° C), the rubber will burn, leaving ordinarily carbon deposits that can be cleaned off as any other dirt would be by any common cleaning method, such as ultrasonics, etc.
If a torch is not available a match, cigarette lighter or gas-stove flame will also work.
Yet another technique is to put the model in an oven at the temperatures mentioned above.
! USE ADEQUATE VENTILATION !
Previously we recommended the following solvents. They work well, although slowly, at dissolving natural rubber. But they are becoming increasingly difficult to find because of their hazardous nature:
Toulene
Xylene
Tri -choloro ethylene (commonly known as Tri-chlor)
Castaldo LiquaCast cannot be removed with any known solvent. The flame method is the only one that will work. Only lowtemperatures are needed, such as those generated by a match or cigarette lighter. Please note that the 
burning rubber will drip and that the drips will burn. Be careful!
Castaldo vulcanizing silicones such as our Super High Strength and Econosil® and Quick-Sil cannot be dissolved. On the other hand, they are unlikely to stick because they are filled with silicone oil and are thus self-releasing. If needed, mechanical means such as ultrasonic cleaners with warm soap and water solutions will often work. 
If nothing else works, you may be willing to try a hot torch flame. This will turn the silicone rubber into a powdery gray ash that can easily be cleaned by conventional means. But the heat required ( about 1,650º F / 900º C ) may damage some types of precious stones. We urge caution when using this method and specifically deny any responsibility whatever for damages that may result from using this method. It is your responsibility to know the heat-resistant characteristics of the stones you are working with and make a judgment on that basis.
Be careful with fire and fumes when burning rubber. Use adequate ventilation and think fire safety!
Your safety and the safety of the stones is, of course, the first consideration. Use your judgment.
