Urethane

Urethane is a particular resin that is often used to coat things (like bathtubs, wood, car bodies, etc.). A true urethane product will be made with two liquid components: the pre-polymer (A) and a catalyst (B). Mixing the two starts a chemical reaction which ends up as a solid.

Urethanes are usually opaque in color, ranging from yellow-tan to white. It can be colored with things like acrlyic paints or transparent dyes. You can purchase a urethane resin that is mostly clear, which is extremely useful for casting gemstones. Of course, the clear stuff is finickier and much more expensive.

The particular brand of casting resin that we've had the most luck with is Synair's Por-a-kast Clear Casting Resin. We've written up a brief overview of our basic urethane casting process.