A construction block system that includes a block with slanted edges that coact with contiguous blacks to define spaces or grooves for receiving cementitious substances. The thickness of the wafer is two-dimensionally mapped and the map is used to control the degree of thermal processing, for example, the intensity of radiation in the line beam to increase the uniformity. A preferred embodiment of the apparatus has a metallic skull crucible, which includes the melt crucible andor the fining vessel.