Under Amenhotep III and IV the art of glazing reached its most brilliant development, both in its colours and in the variety of its applications. Beside the previously used shades of blue and green we meet with purple-blue, violet, a brilliant apple-green, bright chrome-yellow, lemon-yellow, crimson-red, brown-red, and milk-white. Besides the previous uses of glaze for bowls and vases, beads and scarabs, we now meet with a great variety of pendants and ornaments for necklaces, more than two hundred and fifty forms of which are known from the objects and the moulds; also flat emblems and name plaques, with stitch holes or loops at the edge, for stitching on to the muslin dresses then worn. The private person thus wore the king's name on his arm, and the king wore the titles of the sun-god to whom he was devoted. The effect of the white muslin dresses with dazzling blue plaques and natural coloured daisies and other flowers scattered over them, must have been very striking. Another use of glaze was for architectural inlaying (fig. 117). The capitals of great columns were inlaid all over with stripes of red and blue along the palm leaf design, separated into small squares by gilt bands between. The whole capital was thus copied on a vast scale from cloison jewellery. Another use of glaze was for inlaying coloured hieroglyphs in the white limestone walls. This system was carried on in a simpler way into the next dynasty, where a great quantity of cartouches of Sety II are known; and in the walls of the temple of Luqsor are rows of holes of corresponding size, from which they have probably been taken. A favourite form of glazed ware in the XVIIIth and XIXth dynasties is that of the graceful lotus flower cup.
In the XlXth dynasty there is much less variety of glazing; but we meet with the rise of a new industry which was to eclipse all the others in its output. Sety I had many glazed figures of ushabtis of blue colour inscribed in black, or of glazed steatite, in his tomb. Under Ramessu II they became usual for private persons, and for a thousand years later they were made in enormous numbers, usually four hundred being buried in any wealthy tomb. The Ramesside ushabtis are usually green with black inscriptions, rarely white with purple. In the XXIst dynasty they are of very intense blue with purple-black inscriptions, and very roughly made, deteriorating throughout the dynasty. In the XXIInd and XXIIIrd dynasties they are small, and usually green and black. In the XXVth they are mere red pottery dipped in blue wash, or little slips of mud were substituted. The XXVIth dynasty started a different class of very large figures, up to ten inches high, beautifully modelled, with incised inscriptions, back pillar, and beard, always of green glaze; and these deteriorated to Ptolemaic times, excepting that there are some splendid blue ones of Nectanebo, and smaller ones of bright colour with ink inscriptions of private persons of his time.
About the XXVIth dynasty, glazed figures of the gods were made for popular use, and by about 300 B.C. they appear in vast numbers, very roughly moulded. Some of the earlier pieces are very beautifully modelled, and glazed so exactly that the hollows are not at all filled up. A head of Isis (fig. 118), and a half-length figure of a fan-bearer (fig. 119) are perhaps the finest pieces of such work. The latter figure is remarkable for the vigour of the muscles and the overbearing official dignity of the expression.
Great numbers of amulets were also made to be buried with the mummies or worn by the living. The earlier examples are fairly modelled, of apple-green tint; in Persian times they are sharp and dry in form and of an olive-grey colour, but they became very roughly and coarsely moulded in Ptolemaic times. There are some interesting modelled heads of this age, covered with blue or green glaze, such as a Ptolemaic queen, and a woman wearing a face veil. Vases of Greek and Roman styles were also common. A delicate thin ware with Assyrian-esque figures, in white on a slightly sunk blue ground, was made in the Persian time and continued into the Ptolemaic age. Large blocks for legs of furniture, and stands, were also made now. The characteristic colours are of a dark Prussian blue bordering on violet, and an apple-green.
In the Roman age there is an entirely new style. The body of the vase is of a purple-black colour, with a wreath of bright green leaves around it. Such continued almost to Coptic times. The bulk of the Roman glaze is of coarse forms, and bright Prussian blue in tint. The vases have animals in relief, apparently under Persian influence. The flat trays with straight sides are copies of the silver dishes of the time. The old style of glazing continued down to Arab times; a steatite amulet, in the cutting, and colour of the glaze, might well have been of the Shishak age, but for the Arabic inscription upon it. And at the present day some creditable imitations of ancient glazing are made for fraudulent trade at Thebes.
Turning to the more technical matters, the body of the ware is always a porous, friable, siliceous paste; in some cases so soft that it can be rubbed away from the broken surfaces by the finger. The unglazed beads and figures occasionally found can hardly be handled without breaking. This paste was moulded roughly into form, and when dry it was graved with a point to give the detail. If it broke in the fingers a good figure would be stuck together again with a scrap of the paste before glazing. Large objects were made in sections, dried and baked, and then joined up with some of the same paste, and re-baked before covering with glaze. In the XXVIth dynasty there is a beautiful hard stoneware, apparently made by mixing some glaze with the body, enough to fuse it together into a solid mass throughout. The surface of these works is always very fine and smooth, without any face glaze, but only the compact polished body. The usual colour is apple-green, but violet is sometimes found in the early examples of the XVIIIth dynasty.
The colours were rarely anything beyond shades of green and blue. These were produced by compounds of copper; the blue is especially free from iron, which even in traces produces a green tint. The blue if exposed to damp fades white; the green changes to brown, owing to the decomposition of green silicate of iron and the production of brown oxide of iron. This decomposition may go on beneath an unbroken polished face of glaze, changing the glaze to brown. The shades of blue and green were all experimentally produced in modern times by Dr Russell, F.R.S., who succeeded in exactly copying the purple blue, full blue, light blue and French blue, and the green-blues and full greens in more than a hundred tints. The method was indicated by the half-baked pans of colour found at Tell-el-Amarna. Quartz rock pebbles had been collected, and served for the floor of the glazing furnaces. After many heatings which cracked them they were pounded into fine chips. These were mixed with lime and potash and some carbonate of copper. The mixture was roasted in pans, and the exact shade depended on the degree of roasting. The mass was half fused and became pasty; it was then kneaded and toasted gradually, sampling the colour until the exact tint was reached. A porous mass of frit of uniform colour results. This was then ground up in water, and made into a blue or green paint, which was either used with a flux to glaze objects in a furnace, or was used with gum or white of egg as a wet paint for frescoes.
The ovens were small, about two or three feet across; cylindrical pots were set upside down and a fire lighted between them, and the pans of colour rested on the bottom edges of the pots. In Roman times the glazing furnaces were about eight feet square and deep, with an open arch to windward half way up. The vases and dishes were stacked in the furnace upon cylinder pots, and the successive dishes in the piles were kept apart by cones of pottery nearly an inch high. The failure of a furnace-load has revealed the system; by too long heating the glaze soaked through the porous body, and it all settled down and partly fell to pieces.
The other colours used were: for the red a body mixed with haematite and covered with a transparent glaze; bright yellow, the composition of which is unknown; violet in various depths, from a faint tinge on the white lotus petals to a deep strong colour, probably made by copper blue and one of the purples; purple in various strengths from a rich bright tint upon white to a black purple for designs upon blue, all produced by manganese; occasionally purple-blue made with cobalt; dead white, which was doubtless produced by tin as at present.
Before leaving the subject of glazing we may notice the system of moulding pendants and figures in red pottery moulds, of all sizes from a quarter of an inch to three or four inches across. A great variety of these is found at Tell-el-Amarna of the XVIIIth dynasty, and at Memphis of later periods. They sometimes contain the remains of the siliceous paste with which they were choked when they were thrown away. At Naukratis hundreds were found for making scarabs for the Greek trade. The moulded objects were covered with glazing wash, and put into the furnace. Beads were commonly made on a thread, dried, and the thread burnt out; they were then dipped in glaze-wash, and fired. In early times small beads were rolled between the thumb and finger on the thread, producing a long tapering form like a grain of corn.