Читать книгу Encyclopedia of Glass Science, Technology, History, and Culture - Группа авторов - Страница 20

Obsidian (Figure 1), a natural glass found in volcanic provinces in various parts of the Earth, has been known from time immemorial. From arrowheads (Figure 2) to blades of any kinds and purposes (Figure 3), its unique properties made it so valuable to hunter‐gatherers that it was the very first item to be extensively exchanged over long distances [5]. Well before any man‐made object was produced, obsidian thus embodied at an early stage of human evolution the economic notion of competitive advantage, which eventually resulted in its real trade (Chapter 10.1). At the heart of a dynamic corridor between Eurasia and Africa, present‐day Armenia played a significant role in this history as a material source for a wide area in the Near East, initially through moving communities that were carrying their tools with them [6]. Armenia is also important because of the new light it has recently shed on the far‐reaching issue of the expansion of archaic Homo sapiens out of Africa.

Figure 2 The delicate stone knapping of an arrowhead made possible by obsidian in Pre‐Colombian present‐day Arizona.

Source: Photo courtesy Alexandra Navrotsky.

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?