Guide to mould rubbers:

Castaldo White Label^®, the less expensive and firmer of our two grades, has a high concentration of pure natural gum rubber, which makes it resilient and pliable, qualities that the experienced mold-maker values in his efforts to produce high-quality molds in the shortest reasonable time.

Castaldo Gold Label^® contains even more pure natural gum rubber, making it even softer and more pliable. Experienced mold-makers know that this compounds superior qualities can save them substantially on labour costs when used for difficult molds containing undercuts, where a stiffer mold would break delicate wax patterns or would make their production impossible altogether.