As curing progresses, SiliGlass becomes harder and more brittle and the likelihood of breaking increases. Demold SiliGlass within one-half to one hour after mixing to prevent crumbling upon demolding. Contamination from sulfur (e.g., sulfur-based clay), amines, tin compounds, cured polyester resin, some paints and some silicone rubbers may inhibit surface cure of platinum-cured rubbers.