Classical Studies 2700B

[About ten minutes worth of material on Wood will start Thursday’s class. Thereafter we shall have the lecture on Glass, which is quite short, so that we should be more or less back “on track” by the end of the class. CLM.]

GLASS

The early history of glass is quite obscure: it seems to have been a by-product of pottery glazes, containing silica, lime and some kind of soda (i.e., some kind of sodium compound). It began shortly before 3,000 BC and the main purpose was to imitate precious or semi-precious stones (cf. “Egyptian” faience); the product was cut up and ground into beads or shaped for inlay work in jewellery making. Earliest glass vessels are from Mesopotamia c. 2,500 BC, which is much earlier than anything of this kind in Egypt

By 2,000 BC a fairly flourishing glass industry in Mesopotamia, but this is (at some times of the year) a rather damp area (two major rivers, Euphrates and Tigris), and ancient glass does not survive well in these conditions. Discussion of “iridescence” and hydrolytic attack. So, in Egypt, with no real glass industry until beginning of the New Kingdom (result of Hyksos occupation during “2^nd Intermediate Period”, c. 1785 to 1570), or perhaps not even until Egyptian conquests in Syria under Pharaoh Thothmes III (c. 1480-1450), because it is a better place for preservation of glass, more objects survive and Egypt thought of as place where techniques were developed. Some slides showing exx. of glass work from tomb of Tut-ankh-amun (about 1350-1340 BC).

What is glass? R.J. Forbes (Studies in Ancient Technology V² [1966] 114) says: “an undercooled liquid with a very high viscosity” (!!). It is hard, but easily fractured (until recently), usually transparent or translucent and fluid at a high temperature (between c. 750° and 1000° C); problem of avoiding devitrification as glass is cooled; colour effects produced by combining glass with various metallic oxides (only recently are these processes at the molecular level properly understood); also different basic glass “mixes”: bottle glass from sand, potassium carbonate and “red lead” (what Pliny calls “minium”); plate glass from sand, sodium carbonate and calcium carbonate. Because glass is fluid at high temperatures, it can be ladled, stirred, poured and cast; it can be rolled, and made hollow by compressed air—and by human breath; it can also be spun into thin filaments and incorporated into cloth.

Not much glass made in classical Greece (generally it was imported from Egypt or Phoenicia, and glass goblets seem to have been valued on a par with golden cups; however, the great sculptor Pheidias seems to have experimented with it). In ancient times, five main methods of glass handling: a) applying molten glass to a preformed core: how this could be elaborated; b) sections of circular rods cut and arranged round a preformed core (in Mesopotamia from 15^th-13^th cents BC)—ancestor of type (d), below; c) grinding from block of glass—like working with rock crystal; not v. common; d) casting: by contrast, a v. common technique, especially so in Hellenistic period (slides on this); e) blowing, invented late in last century BC, apparently by Phoenician or Jewish glassmakers; knocked out almost all other techniques. This E. Mediterranean area incorporated into Roman empire at about the time glass blowing was discovered; so taken up by Romans and technique spread all over empire; even glass window-panes, though way of making them seems quite odd. Exx. of Roman glass on slides. Most spectacular of all were “cage” glasses (called diatreta). Finally, question of lenses.