Firmer Than Composimold-Original For Two Part Moulds Or Polymer Clay Push Moulds ComposiMold-Firm is a more powerful mould making material than ComposiMold-Original. It is also a 100% reusable mould making material that works by melting and pouring. Many casts can be made using the same mould. ComposiMold-Firm mould is flexible, rubbery, thermoplastic that is great for small mould parts that require a stiffer mould making material. It is compatible with many different casting materials including clays, plaster, cement, epoxy, polyurethane, and many others.ComposiMold-Firm conforms to ASTM D4236, safe as an art material.