Encyclopedia of Glass Science, Technology, History, and Culture. Группа авторов

Figure 3 The striking stone‐knapping difference between a biface (left) and Levallois point and blade, all made from obsidian (right); length: 20 cm: (a) Acheulean hand axe produced by serial removal of small flakes with a soft hammer (Kuchak‐3 open‐air site, Aparan Depression, Central Armenia); (b) Levallois Mousterian point, with its plano‐convex profile, produced before the repreparation of core convexities, and the recurrent method, in which multiple Levallois flakes are detached before repreparation (Barozh‐12 open‐air site, Ararat Depression, Eastern Armenia); (c) Regular flake of the Chalcolithic period produced by pressure flaking from a prismatic core with the aid of a lever (Mastara‐1 settlement, Ararat Depression).

      Source: Photos courtesy Boris Gasparyan.

According to a claim often made, this expansion followed the important technical change from bifacial to Levallois technique of stone knapping (Figure 3, cf. [7] for their differences). At the Nor Geghi‐I site, near Yerevan, both types of tools actually coexist within alluvial sediments sandwiched in between lava flows dated to 441 000 ± 6 000 and 197 000 ± 7 000 years [8]. From a fundamental standpoint, the synchronic use of both techniques by a single human group at this site thus indicates instead that, after human dispersion, the transition occurred independently within geographically distinct areas. From a practical standpoint, the change allowed better tools to be obtained so much faster from a large core (Figure 1) and with little waste. One could in fact conclude from the incredibly high abundance of artifacts buried in a Middle‐Paleolithic site such as Barozh 12 [9], next to the Arteni Complex Volcano (Eastern Armenia), that the concept of disposable object was born with obsidian in the Paleolithic!

      Man‐made glass appeared considerably later, only three and a half millennia ago in the Late Bronze Age in a wide area ranging from the Near East to Egypt and Greece (Chapter 10.2). The vividly colored but expensive material newly produced was originally the preserve of elites who had recognized its aesthetic and practical interest. After 15 centuries of technical improvements and decreases of production costs, it became a basic commodity in the Roman Empire as acknowledged by Petronius (first century CE) in the Satyricon where one of his characters uttered: “You will forgive me if I say that personally I prefer glass; glass does not smell. If it were not so breakable I should prefer it to gold; as it is, it is so cheap” [10]. This chemical inertness achieved at reduced cost was of course one of the early assets of glass. As we now know, others were resulting from its lack of long‐range atomic order, which makes forming in the most diverse shapes and sizes possible, produces optical isotropy, gives much flexibility in terms of raw materials and coloring elements thanks to the almost limitless extent of its solid solutions, and is at the source of mechanical properties in principle limited only by the strength of interatomic bonds thanks to the lack of weak grain boundaries.

How was it figured out that glass could completely lose its vivid colors, which first attracted man's interest, we do not know. The transparency now so closely associated with glass was first achieved for very special pieces such as cups made in Achaemenid Persia in the fifth century BCE (Chapter 10.0, Figure 1a). But it took several more centuries before transparency became common. The existence of pure, natural carbonates commonly termed natron was the key ingredient to achieve it at a large scale at the beginning of our era [11]. Especially in the Levant, the competitive edge acquired by glassmakers thanks to this substance was such that it led to the establishment of a world market: finished items and glass ingots were traded along well‐established commercial routes to be exported as far as East Africa and India [12], the ingots to be shaped locally in small workshops (Chapter 10.3). A first glimpse at globalization?

      1.3 A Multifaceted Material

      Glass has always aroused much curiosity by its virtue of embodying almost unlimited possibilities for transforming matter. Until the end of the nineteenth century, industrial illustrations of such transformations were the metamorphoses undergone by the large glass pieces that were first blown before being opened and flattened to yield flat panes with the neat fire finish required for transparency (Chapter 10.8). Nowadays, who has never been captivated by the work of a blower, by the action of a delicately controlled fire that gives birth to the most surprising shapes and, in a way, makes the material living for an instant? Even the proverbial brittleness of glass is part of this powerful imaginative world: its fracture indeed seems as unpredictable as it is dramatic, as illustrated by a tempered drinking glass suddenly exploding after several bounces when falling onto the ground.

      To this kind of amazement also contributed early the miracles wrought by glass ever since it first restored sight to visually impaired people in the thirteenth century (Chapter 10.10). It is thus no wonder that Leonardo da Vinci (1452–1519) devoted efforts to design a device for machining eyeglasses. Shortly after, the transparent glazing of windows opened houses on the outside world at about the same time as the telescope and the microscope led to the discovery of the universe from the infinitely large to the infinitely small (Chapter 10.10). Grinding of optical lenses was then extensively practiced by Galileo Galilei (1564–1642) himself and considered a trade worth earning a living by the eminent philosopher Baruch Spinoza (1632–1677). That glassmaking had something special is actually indicated by the fact that, in France, it was long the only trade that the nobility could practice as gentlemen glassmakers without losing its special status.

      To acknowledge all what civilization was owing to this material, the polymath and glassmaker Mikhail Vasilyevich Lomonosov (1711–1765) wrote in Russia a long poem entitled Letter on the use of Glass. “A whole year would hardly suffice me to reach the end of worthy praise for Glass” [13], Lomonosov thus claimed when mentioning not only the telescope, the microscope, or the barometer, but also the thrilling electrical researches of his time based on the accumulation of charges on the glass disks of electrostatic machines (Chapter 10.10). Such was the interest raised by the vitreous (positive) and resinous (negative) electricities “that people of all genders and ranks were then begging for the favor of being subjected to electric shock, to the point that the noble and courageous Professor Georg Matthias Bose (1710–1761) said with philosophical heroism: I would not regret dying of an electric shock, since the account of my death would provide the subject of an article in the Memoirs of the Royal Academy of Sciences of Paris” [14]. Could this admirable philosophical heroism have been elicited by a material other than glass?

      At the same period, glass became the source of another kind of emotions when the famous Benjamin Franklin (1706–1790) was inspired by “the sweet tone that is drawn from a drinking glass, by passing a wet finger around the rim” [15] to design in 1761 the glass armonica whereby it was a set of overlapping wet glass cones of different sizes that was rotating to emit a sweet, ethereal, or pathetic tone through the friction of fingers. The instrument met with rapid success such that, beginning with Wolfgang Amadeus