Shell Mold. The form from which a thin casting is made. In medallic work shell molds are employed for casting plaques which have high relief. The mold for the back side forms the depressed area congruent with the high relief on the obverse. This forms a casting which can have uniform thickness irrespective of the high relief reduceing the weight and curtailing the metal cost somewhat. The cast plaque would be called cast hollow for these reverse depressions. It may remain single-sided, or have a backplate attached to the reverse. Shell molds are typically thought of as the mold for statues and statuary, they are molds which have a core built into them for making the cast piece – not solid – but a thin shell forming the design.