Shell Shock FAST and Shell Shock SLOW are thixotropic plastics that self-thicken when mixed and can be brushed onto vertical surfaces or into rubber molds. Material cures at room temperature with virtually no shrinkage to a hard, durable plastic. Fully cured castings are rigid and can be sanded, primed and painted. Shell Shock is ideal for making fast, lightweight rigid molds for creating silicone appliances and effects (use as a replacement for gypsum molds). You can also brush a “gel coat” into a rubber mold and back it up with rigid foam, creating a highly detailed lightweight casting.