There has been much misunderstanding about the age of glass in Egypt. Figures of smiths blowing a fire with reeds tipped with clay have been quoted as figures blowing glass, though no blown glass is known in Egypt before Roman times. A cylinder of glass of King Pepy has been quoted; but this is really of clear iceland-spar or selenite lined with coloured paste. A panther's head with the name of Antef V has been called glass, but it is really of blue paste. Various pieces of inlaid stone jewellery have been mistaken for glass, but none such is known till late times.
There does not seem to have been any working of glassy material by itself, apart from a base of stone or pottery, until after 1600 B.C. The earliest dated pieces are an eye of blue glass imitating turquoise, with the name of Amenhotep I (1550 B.C.), and a piece of a glass vase with an inlaid name of Tahutmes III. Beads of this age are plain black with a white spot on opposite sides; black and white glass cups probably belong to the same date. The variety of colours quickly increased, and by the time of Amenhotep III and IV, about 1400 B.C., there were violet, deep Prussian blue, light blue, green, yellow, orange, red (rare), clear white, milky white, and black.
The designs were entirely ruled by the method of manufacture. The glass was never cast, but was worked as a pasty mass, and all the decoration was made by inlaying threads of glass drawn out to various thicknesses. The actual production of the glass we deal with below. The patterns on a vase or bead were produced by winding threads around the body, and then dragging the surface at regular intervals (figs. 120, 121). If dragged always in one direction, it made a series of loops or U pattern; if dragged alternately each way it made an ogee pattern. Around the neck and foot a thick thread was often put on, with a thin thread spirally round it, usually white with black spiral. The forms of the vases are those usual in other materials at this period, such as
121. Vases (XVIIIth dynasty).
122. Mosaic (late).
This same method was followed in the glass found at Cumae near Naples, dating from about 700 B.C. It is distinguished from the Egyptian fabric by a duller surface and duller colouring, and a common form unknown before is
This later glass is usually mixed with the earlier in museums, and occa sionally it is difficult to distinguish it; but both the forms and the colour leave very little doubt as to the age.
This system of winding threads of glass was usual for beads also. A mere chip of a glass bead can be distinguished, whether Egyptian or Roman, by the direction of the streaks and bubbles in it. The early glass is all wound, with lines running around; the Roman glass is all drawn out and nicked off, with lines running along; the medieval and modern Venetian beads are again wound, and some of the recent ones closely imitate Egyptian dragged patterns, but can be distinguished by the opacity of most of the colours.
The XVIIIth dynasty workers also cut and engraved glass, though but rarely. They sometimes produced a clear glass entirely free of colouring, even in a thickness of half an inch. About the XXIIIrd dynasty (750 B.C.) a clear, greenish Prussian blue glass was usual for beads, and continued to Persian times for scarabs (500 B.C.). Rather later, about 400 - 200 B.C., there appears a large development of opaque glass figures of hieroglyphs, cut and polished, to inlay in wooden caskets and coffins. Opaque red and blue to imitate jasper and lazuli were the most usual colours. Figures of the four genii of the dead and other usual amulets were commonly made by pressing the glass into moulds while heated. A favourite colouring for such was a deep, clear, true blue, backed with opaque white to show up the colour. About the later Ptolemaic time and through the Roman age the main work in glass is that of minute mosaics (fig. 122). They were built up with glass rods, heated until they half fused together, and then drawn out so as to produce a great length of much reduced section. Thus patterns of extreme delicacy were produced; and one single piece of construction could be cut across into a hundred slices, each repeating the whole design. The patterns are sometimes purely Egyptian, as ankh and was alternately, but more usually Roman, such as heads and flower patterns. Such mosaics were mounted in jewellery, or, on a coarser scale, set in large designs for caskets and temple furniture.
The characteristic of Roman times is the use of blown glass. The cups, bottles, and vases were nearly all blown, often with threads woven around, dabs attached and impressed, or patterns stamped while soft. The feet of cups were modelled into form while pasty, the tool marks showing plainly upon them. Ornamental stamps were pressed on soft lumps put on the sides of vases. Such stamps became used for official marks, and in early Arab times they registered the substance for which the glass measure was intended, also the amount of the capacity, and the maker's name in many cases. Another main development of Byzantine and Arab glass was for weights, usually to test gold and silver coins, but also for larger amounts up to a pound. These weights bear the stamps of the Byzantine epochs in a few cases, but are found by the hundred of the VIIIth to Xth centuries, and by the thousand of the Xth to XIth centuries, dying out at the early crusading age.
We now turn to the purely technical side, to describe the process of manufacture in the time of Amenhotep IV, about 1370 B.C., when it is best known to us, from the remains of the factory at Tell-el- Amarna. A clear glass could be produced, which was usually not quite colourless, but sufficiently so to take up various colours. It was free of lead and borates, and consisted of pure silica from crushed quartz pebbles, and alkali doubtless from wood ashes. It was fused in pans of earthenware. This glass was coloured by dissolving the blue or green frit in it, or mixing other opaque colours. Samples were taken out by pincers to test the colour at different stages. The whole mass was fairly fused, and then left to get cold in the earthen pan, which was about four or five inches across, and held half an inch to an inch deep of the glass. When cold the pan was chipped away, the frothy top of the glass was chipped off, and lumps of pure glass were obtained free from sediment and scum. A lump of glass thus purified was heated to a pasty state, and patted into a cylindrical form, then rolled under a bar of metal, which was run diagonally across it, until it was reduced to a rod about the size of a lead pencil, or rather less. Such a rod was then heated, and drawn out into "cane" about 1/8 inch thick. Every vase was built up from such cane.
For making a vase a copper mandril was taken, slightly tapering, of the size of the interior of the neck. Upon the end of this was built a body of soft siliceous paste, tied up in rag, and baked upon it, of the size of the interior of the intended vase.
The marks of the string and cloth can still be seen inside the vases. On this body of powdery material glass cane was wound hot until it was uniformly coated. It was re-heated by sticking the end of the mandril into the oven as often as needful; glass threads of various colours were wound round it; and the whole was rolled to and fro so as to bed in the threads and make a smooth surface. A brim, a foot, and handles were attached. Finally, on cooling, the copper mandril contracted, and could be taken out of the neck, the soft paste could be rubbed out of the interior, and the vase was finished. The final face is always a fused surface, and was never ground or polished.
A similar mode was followed for the glass beads. The thread of glass was wound upon a hot copper wire of the size of the hole required; and after piling on enough, and completing the pattern of colour the wire contracted in cooling and could be withdrawn. The little point where the thread of glass broke off can be seen at each end of the beads.