Urethane Casting Notes


MOCHI > The Workshop > Crafting > Crafting Techniques > Casting > Urethane Casting Notes

During Casting

When using dyes to color clear urethane, more dye is usually better than less dye. Unless the final cast will be attached to something very light or white, it will be difficult to actually see the color.

Some of the books that we've read suggest that plaster is a bad mold for urethane. The urethane sticks so hard to the mold that you'll never get it out. We've never tried using a plaster mold -- but we have seen this with some of the thin plastics used for making soap.

One of the traditional "craft-y" things to do with clear cast urethanes is making paperweights. You can imbed shells, fibers, gravel, glass beads -- all sorts of things. There are special powders that can be used to get funky effects: metallic powders, fine-grained sand, porcelain powder, etc. Depending on what kind of casting resin you use, you can also buy additives that will speed up the polymerization process or slow it down, make the resin UV-resistant, or make the final product stronger.

Post-casting

Urethane casts can be modified after casting. With the right tools, it can be cut (to make a faceted gem) or can be buffed until it's really shiny. If you're going to do this, be very careful to use an air filter, goggles, and a set of clothes that you're willing to trash. The resin produces an extremely fine powder.

Some pieces get a "tacky" feel on the surface. If that feel is still there after a few days, you might want to spritz it with some clear acrylic spray to seal it.