I sculpted the original 3D pattern for this G scale pewter workman figurine casting with Super Sculpey™, over an armature.   The Super Sculpey™ darkened, but it held up well in my 325°F vulcanizer.  The vulcanized rubber (silicone) mold held up well through repeated pours of molten pewter.  The castings did not shrink short.  And, as you can see, there was no flash using this gravity pour mold.