Polyurethane (Smooth-Cast 300)

Due to its low viscosity, this casting resin is capable of capturing excellent detail, and yields casts that are virtually bubble-free.  The resulting polymer is bright white, opaque and incredibly hard despite its rubbery appearance. It is also resistant to moisture, moderate heat, dilute acids and mild solvents. However, unpainted casts will turn yellow over time, especially when exposed to UV light.

Regardless of the end-product or even type of polyurethane you are using, the way in which you use polyurethane resins is always the same: the raw materials come in two parts, a liquid isocyanate (a very reactive chemical derived from petroleum) and a polyol (a long-chain alcohol), which are mixed to a specified ratio to create a reacting liquid, which is then poured into a mould or onto a surface and left until it cures to form a solid object. This relatively low-tech process makes it a useful material for tinkering and making prototypes.

This particular polyurethane plastic is commonly used for casting small stage and film props like replica guns, swords and Star Trek Klingon Disruptors.