Polysulfide Rubber

Smooth-On has been making polysulfide rubber since World War II. Unlike other mold making materials, polysulfides are not bothered by sulfur or moisture present in many modeling clays favored by sculptors. They continue to be used by art bronze foundries and as an important part of the lost wax process. Tire mold makers like the fact that polysulfide can be altered using a hot knife to modify patterns quickly.