the american society for testing materials defined glass as &lsquoan inorganic product of fusion which has cooled to a rigid state without crystallizing&rsquo astm, 1965. chemically, we know that glass is made by cooling a heated, fused mixture of silicates, lime and soda to the point of fusion. morey says that, after cooling, it attains a condition which is continuous with, and analogous to, the liquid state of that substance, but which, as a result of a reversible change in viscosity, has attained so high a degree of viscosity as to be for all practical purposes solid morey, 1954.
