Glass

The word “glass“ refers to the solid phase of a material with no long-chain molecular order. It is used almost interchangeably with “amorphous,” “non-crystalline,” and “vitreous.” Glass is a disordered structure, as compared to a crystalline material that exhibits a symmetrical, ordered structure. The most common glasses are oxide based, such as silicates (SiO₂), borates (B₂O₃), germinates (GeO₂) or mixtures of these.

Fused silica used in optical fiber and capillaries is a very high quality, synthetic glass of almost pure SiO₂ (silicon dioxide). Glass is also found in nature, as the volcanic material obsidian and as the enigmatic objects known as tektites. Glass is usually transparent, but can also be translucent or opaque. The color may vary with the constituents of the particular glass.

Due to its structure, glass materials do not have specific melting points, but transition from solid to molten over a temperature range. This allows glasses to be easily shaped and formed. Glasses can also be modified with additives to adjust certain physical properties such as strength, thermal expansion, transparency, index of refraction, viscosity, dielectric strength, or other characteristics. The ease of processing and modification has led to many useful applications of glass from windowpanes to insulators to optical fibers.