Welcome to the Glass Age

200 example, for continuous molding at low and very low viscosity. This is not only what enabled today’s glass industry, but also what makes the glass route attractive to new ranges of materials: where crystal (and often particle) processing is not efficiently or sustainably feasible in the desired shapes and geometries, glass forming procedures are sought which offer fully new opportunities (such as most recently in the world of metal- organic frameworks). The greatest leaps in glass innovation were and are still process-related (Figure 13.2). They have repeatedly and in a surprising continuity led to major societal changes, from the invention of the glass blowing pipe to industrial firing systems and continuous melting units, the manufacture of flat sheet, or high-purity silica glass and the advent of optical telecommunication. And this is notwithstanding parallel developments in related fields, albeit concerning glasses in different material classes: extrusion, injection molding and the many other ways of processing polymers or, e.g., the preparation of metallic glasses which has arrived at a crossroads towards innovating future processing methodology. Order in disorder The glassy nature implies their unexpectedly complex properties. For a glass of the very same chemical composition, vastly different physical properties can still be obtained as a function of the conditions at which the glass transition was conducted: many if not all properties of a glass depend on the cooling rate and pressure at which it was produced. This only adds to the effect of chemical composition and topology; in technological development, glasses have thus far largely evaded knowledge-based predictability and control of the more intricate combinations of properties such as required by modern material applications. Again, the single most important communality among all types of glass is their fundamental difference to crystalline materials: on the one hand, like liquids, glasses exhibit high macroscopic and microscopic homogeneity. They do not consist of grains, particles or different material phases. On the other hand, they exhibit Figure 13.2. Glass milestones and the generations of glass technology. Source: Adapted from Ref. [7] under CC-BY license. © The Authors.