Opalescent Glass Solid color, opalescent glasses. These non-variegated products are highly reflective in nature and thus especially popular for mosaic and mural application. With back lighting, natural or artificial, they reveal a captivating, luminescent glow. System 96® Products formulated and "Tested Compatible" especially for fusing, slumping and other hot glass work. This Spectrum line of sheet glass is complemented by many specialty glass products, including glass frits, noodle, stringer, dichroic glass, and casting billets, made and supplied by System 96 partner companies. All System 96 products are tested against an identical standard to insure compatibility of viscosity and expansion coefficient.