Notwithstanding the prodigious output in each of the several varieties, it is a remark able fact that there were few large glass-mak ing establishments, a great part of the produc tion being provided by artificers working on a small scale. The period was also remarkable for the variety of colors employed in glass-mak ing, for the numerous processes of manipulation and for the large number of decorative motives; and it is astonishing to what proficiency the glass worker had attained in all these matters. Among colors, blues and greens were most largely used, with many shades of each; then followed purple, amber, brown and rose color. These were transparent colors. In opaque colors, white, red, blue — in tones from lapis lazuli to turquoise,— yellow, green and orange. The yellows and greens were in various tones also. These were mainly self-colors but the range was extended by manipulating processes. A most interesting, and technically a very dif ficult, process in manipulation occurs in the making of the blank forms used in the glass we know as °cameo.* The Portland vase is the best-known example of this class. The Ro mans produced a vast quantity of it, though it is not quite certain that they originated either the methods of uniting the two bodies of glass required for the cameo effect, or the processes of sculpturing the ornamentation. Transparent blue was the usual ground color for cameo glass and opaque white almost invariably the coating from which the ornamentation was carved. Oc casionally other colors were used. In this case the opaque white was inside the vessel, then a strata of clear glass and then the color or colors from which the ornament was fashioned. Pressed glass was one of the processes for certain forms of cameo. Discs, medallions and panels were i produced in large quantities where replicas were required to complete a decorative scheme. It was not usual to duplicate vase forms in cameo ornamentation.
Black glass was largely used in making arti cles upon which food was served. It was also used — as was brown and other colors — in making imitations of onyx. The various uses to which glass of the "mosaic" class could be put were made the most of by the Roman work men, though some of the motives were of Egyp tian origin. The "mine fiori" class, imitations of porphyry, and serpentine, agates and granites, were used in architectural decorations, even to pavements and wall tiles. The manipulation of threads of colored glass into patternings of the *vitro di trine order was a well-practised art.
A well-practised form of decorating glass by use of gold leaf was invented by the Romans. The gold was embedded in the substance of glass at first, but later a patterning was made of it on the surface. These patternings were occasionally embellished by a second applica tion of molten colored glass enclosing the gold leaf. By one, or both, of these methods, pic torial effects were occasionally produced. In scriptions in this ornamental form sometimes appeared. In the manufacture of personal orna ments in glass, a process and effect very nearly approaching the cloisonné of later times, was carried to a high state of perfection by the Roman craftsmen. An effect, very much of the appearance of the silver of our own time was made at Rome, but by directly oppo site processes. The design was pierced in the silver vessel and the colored glass blown into it. The same idea has been experimented with
in quite recent times, but the annealing process developed difficulties.
Malleable glass was talked of at Rome. It evidently was considered a menace to the in dustry, as the invention and the inventor passed out tragically by the edict of a Caesar. Glass toughened by annealing in oil is its modern equivalent.
Glass prisms were known; "when the sun shone through them they gave the colors of the rainbow." Here we have the early form of the chandelier pendant. Magnifying glasses and lenses were also known.
The Romans preserved their choicest wines in amphora of glass. Window glass was used by the Romans at a time when mica, alabaster and certain kinds of shells were also capable mediums for transmitting light into the homes.
Though the Romans knew that highly pol ished black glass, or clear glass blackened on one side, would reflect images, it is not known for certain whether or not they made glass mirrors. The manufacture of Roman glass ap pears to have weakened as an industry after the fall of the empire, in all branches except mosaics. This class seems to have been con tinued, though with varying success, up to the 9th century.
Eastern Countries and The art of glass-making seems to have been culti vated in ancient time in most of the Eastern countries, and though there is no way of link ing the present with the past in this connec tion, there is little doubt the chain has not been broken for any lengthened period, and glass is made to-day in some of the countries that saw the blow-pipe operating in pre-Christian times. One writer says —"Glass furnaces flamed on the Syrian coast for 25 centuries.' Another—"The Sidonians carried the art of glass-making to great perfection"; and mention is made of ''the celebrated Tyrian glass.' Glass was made at Antioch by the Jews; at Damascus; at Shiraz in Persia ; at Smyrna. A large, part of the ancient glass manufacture was in small objects, as vases, perfume bottles. personal ornaments and articles for sacred pur poses. Articles of general utility were but a small part of the product. It may be, however, that such articles are unknown to us from the fact that they were not of sufficient or value to preserve. There were also some curious purposes to which glass was put. In the 12th century "a coffin of glass" is mentioned; also °a plate of glass used to keep dust from settling upon a painting.° Byzantine glass has a long record, its two best periods being the 6th and the 10th centuries. It advanced considerably after the fall of the Roman Empire, probably on account of the aid obtained by securing the craftsmen who had worked at Rome. The great work of the Byzantine glass-makers for some time was in mosaics for church use. In the 10th and 1 lth centuries personal ornaments were a feature of production, in some of the methods earlier practised at Rome. They also used the Roman methods of pressing glass cameos. They were experts in the art of enameling and gilding of glass, but as the Byzantine decorative motives were employed at other eastern glass-making . centres there has always been some difficulty in identifying their work. We know little of what, they did in glass for domestic purposes. Byzantine glass making passed out when Venetian came in.