A related property is its unusually high thermal shock resistance. For example, thin sections can be heated rapidly to above 1500 C and then plunged into water without cracking. Effects of temperature Fused quartz is a solid material at room temperature, but at high temperatures, it behaves like all glasses. It does not experience a distinct melting point as crystalline materials do, but softens over a fairly broad temperature range. This transition from a solid to a plastic-like behavior, called the transformation range, is distinguished by a continuous change in viscosity with temperature.
Viscosity is the measure of the resistance to flow of a material when exposed to a shear stress.
The temperature at which the internal stress is substantially relieved in four hours. The temperature at which glass will deform under its own weight, a viscosity of approximately 10 7.6 . The softening point of fused quartz has been variously reported from 1500 C to 1670 C, the range resulting from differing conditions of measurement. Optical transmission properties provide a means for distinguishing among various types of vitreous silica as the degree of transparency reflects material purity and the method of manufacture. Specific indicators are the UV cutoff and the presence or absence of bands at 245 nm and 2.73 m.