What is Glass?


The Structure of Glass
Glass is hard and rigid to the touch. It is brittle. Tending to break in sudden contact with a hard surface, and yet it is described as a liquid in chemical terms. So, curiously, many of the vessels designed to hold liquids are actually a form of liquid themselves.
Glass, when cooled to rigidity bears these basic qualities, but when heated its qualities tend to change entirely. It begins to soften until ductile, and if heated sufficiently will flow like water.
Defined as a metal, glass has, however, certain unique properties not common to other metals. The most important of these is that it has what we call a ductile point rather than a melting point. As it is heated it becomes liquefied and fluid, and attains a plasticity which renders it ideal for shaping by various means or blowing into a form.
Glass is a surprisingly basic material.It is a compound of Silica (Silicium dioxide) and ferrous oxides. But it is the molecular structure of glass which gives it its most extraordinary characteristic of being not liquid and at the same time not a solid of crystalline structure in the true sense. It occupies a unique structural place between in two, and is defined as spure-cooled liquid. When we look at the structure of glass through the microscope, we notice that the molecular formation is quite unlike the regular arrangement of molecules in a crystalline structure, as in other solids. If anything, the random arrangement of molecules is most like that of liquids. But although we define glass as a liquid it is, in fact, extremely dense, with a high specific gravity, which prevents it from Warping Or changing shape under the effects of gravity.
Not only is it defined as a liquid, glass really is liquid, hence its transparency. A true liquid has no intermal joins. Light passing through it is neither refracted nor reflected, apart from a slight refraction of the light ray as it passes through the surface of the glass. This is, of course, true only of high quality transparent glass. The presence of oxides in glass allow the rays of the visible spectrum to pass through it. This is how tinted glass is made. Glass can also be given extraordinary degrees of opaqueness and translucency by the addition of various modifying substances.
Prof.Küçükerman Önder, The Art of Glass and Traditional Turkish Glassware, s:20-21