Which ComposiMold do yiou use? If in doubt, use ComposiMold-Original. It works for most options and all ComposiMolds are food contact safe. But all are designed to help you make great molds.
ComposiMold-Flex is designed for soft casting materials such as soap, chocolate, wax, and butter. The more flexible mold making material allows you to bend the ComposiMold away with less of a change of breaking the soft casting materials.
ComposiMold-FC (Food Contact) and ComposiMold-Original are the same mold making materials, just labeled separately so you can keep one for food and one for plastics and other not as tasty casting materials like plastic, concrete, and others . The ComposiMold Original is a good compromise between soft and firm.
ComposiMold-Firm is specifically designed for Polymer Clay or Polymer Metal Clay push molds.
The ImPRESSive Putty is ideal for fast molds, higher temperature casting materials such as fast cure urethane resins. The ImPRESSive Putty is not certified for food yet.