Vitrum
（
ὕαλος). Glass. The Egyptians made glass at a very early
period, the oldest existing specimen being a blue vase of opaque glass now in the British
Museum, as old as the sixteenth century B.C. Cups and bottles of uncertain date have been
taken in considerable numbers from the tombs and mummy-cases. In the paintings of Beni-Hassan
(about 2300 B.C.) the process of glass-blowing is clearly depicted. The Assyrians likewise
made admirable glass, the oldest existing specimen being a sort of bottle of green glass found
at Nimroud, and dating from 719 B.C. It is now in the British Museum.
A story has been preserved by Pliny (
Pliny H. N.
xxxvi. 191) that glass was first discovered accidentally by some merchants who, having
landed on the Syrian coast at the mouth of the river Belus, and being unable to find stones to
support their cooking-pots, brought for this purpose from their ship some of the lumps of
nitre which composed the cargo. This being fused by the heat of the fire, united with the sand
upon which it rested and formed a stream of vitrified matter. The Phœnicians
probably learned the art of glass-making from the Egyptians; but the tale is no doubt
connected with the fact recorded by Strabo (xvi. p. 758) and Iosephus (
Bell.
Iud. ii. 9), that the sand of the district in question was esteemed peculiarly
suitable for glass-making, and exported in great quantities to the workshops of Sidon, long
the most famous in the ancient world. Alexandria, another centre of the industry, sustained
its reputation for many centuries; Rome derived thence a great portion of its supplies, and as
late as the reign of Aurelian we find the manufacture still flourishing (
Pro Rabir.
Post. xiv. 40; Strabo, l. c.; Martial, xi. 11; xii. 74; xiv. 115; Vopisc.
Aurel. 45).
Homer does not certainly mention glass, but at Mycenae and Tiryns glass beads and other
ornaments have been found. The words
ὕαλος and
ὕελος in the early Greek writers (e. g.
Herod.iii. 24) do not always refer to glass, but often to rockcrystal, rock-salt,
amber, or alabaster; and it is not till Theophrastus, the pupil of Aristotle, that the word is
surely to be rendered “glass.” Of the Roman writers, Lucretius is the
first to use the term
vitrum (
iv. 604;
vi. 991), but it must have been known at Rome long before this time,
as Cicero (l. c.) speaks of it as a common article of merchandise. Phœnician glass
is found in the Etruscan cemeteries at Tarquinii dating from the eighth
century B.C. Scaurus in his temporary theatre, erected in B.C. 58, used glass freely in the
interior decoration (see
Theatrum); and the
Augustan poets often mention the substance (e. g.
Georg. iv. 350;
Aen. vii. 759; Ovid,
Amor. i.
6, 55;
Hor. Carm. iii. 13, 1). Pliny
states that glass was made in Italy, Gaul, and Spain, and that drinking-cups of glass had
superseded those of gold and silver (Pliny ,
Pliny H.
N. xxxvi. 192-199). Under Alexander Severus we find the glass-makers (
vitrearii) enumerated in the tax-lists with other artisans. Strabo notes the
cheapness of glass, and says that a glass drinking-cup sold in his time for half an
as, or less than a cent.
The following are the chief uses to which glass was applied:
（
a) Bottles, vases, cups, and urns for the ashes of the dead (
cineraria). Of all of these great numbers exist, in a great variety of forms
and colours, some having been blown into moulds so as to take the shape of—e. g. a
bunch of grapes, a sea-shell, a negro's head, etc. (See illustration, s. v.
Diatreta.) The finest of all under this class is the
celebrated Portland Vase in the British Museum, found in the sixteenth century near Rome. See
Portland Vase.
（
b) Glass pastes giving fac-similes of engraved precious stones. These
were worn by those who could not afford real gems (Pliny ,
Pliny
H. N. xxxv. 48). Precious stones were also imitated in glass with very
great skill, so that only experts could detect the imposition. The sapphire, amethyst,
carbuncle, and especially the emerald, were the oftenest counterfeited (Pliny ,
Pliny H. N. xxxvii. 197; Trebell. Poll.
Gall. 12; Seneca,
Epist. 90; Isidor.
Orig. xvi. 15, 27). See
Gemma.
（
c) One very elegant application of glass deserves to be particularly
noticed. A number of fine stalks of glass of different colours were placed vertically, and
arranged in such a manner as to depict upon the upper surface some figure or pattern, upon the
principle of a minute mosaic. The filaments thus combined were then subjected to such a degree
of heat as would suffice to soften without melting them, and were thus cemented together into
a solid mass. It is evident that the picture brought out upon the upper surface would extend
down through the whole of the little column thus formed, and hence, if it was cut into thin
slices at right angles to the direction of the fibres, each of these sections would upon both
sides represent the design which would be multiplied to an extent in proportion to the total
length of the glass threads. Further, if the column is heated and drawn out, the design
becomes proportionately minute. When these sections have been again fused together side by
side, the result is
millefiori glass. Many mosaic pavements and
pictures (
opus musivum) belong to this head, since the cubes were
frequently composed of opaque glass as well as marble. See
Musivum Opus.
（
d) One method of decoration employed by the ancients consisted in
enclosing designs in gold-leaf between two layers of transparent glass. This is most common
from the third century A.D., when small Christian subjects are thus represented.
（
e) Thick sheets of glass of various colours appear to have been laid
down for paving floors, and to have been attached as a lining to the walls and ceilings of
apartments in dwelling-houses, just as
scagliola is frequently employed in Italy. Rooms fitted up in this way
were called
vitreae camerae, and the panels
vitreae
quadraturae. Such was the kind of decoration introduced by Scaurus for the scene of his
theatre, not columns nor pillars of glass as some, nor bas-reliefs as others, have imagined
(Pliny ,
Pliny H. N. xxxvi. 189;
Sil. i. 5, 42; Seneca,
Ep. 76; Vopisc.
Firm. 3).
（
f) The question whether glass windows were known to the ancients
has, after much discussion, been set at rest by the excavations at Pompeii, for not only have
many fragments of flat glass been disinterred from time to time, but in the
tepidarium of the public baths a bronze lattice came to light with some of the panes
still inserted in the frame, so as to determine at once not only their existence, but the mode
in which they were secured and arranged (Mazois,
Ruines de Pompéi,
iii. p. 77).
For the use of glass in mirrors, see
Speculum.
The numerous specimens existing prove that the ancients were well acquainted with the art of
imparting a great variety of colours to their glass; they were probably less successful in
their attempts to render it perfectly pure and free from all colour, since we are told by
Pliny that it was considered most valuable in this state. It was wrought according to the
different methods now practised, being fashioned into the required shape by the blowpipe; or
cut, as we term it, although “ground” (
teritur) is a
more accurate phrase, upon a wheel; or engraved with a sharp tool, like silver (Pliny ,
Pliny H. N. xxxvi. 193). The process was
difficult, and accidents occurred frequently (
Mart.xiv. 115).
The art of etching upon glass, now so common, was entirely unknown to the ancients, since it
depends upon the properties of fluoric acid, a chemical discovery of the last century.
Petronius and Dio Cassius assert that malleable glass was discovered in the reign of the
emperor Tiberius. They tell a story of how a man demanded an interview with the emperor, and,
on being admitted, showed him a glass vessel and then dashed it violently upon the ground.
When taken up, it was neither broken nor cracked, but dinted like a piece of metal. The man
then produced a mallet, and hammered it back into its original shape. The emperor inquired
whether any one was acquainted with the secret, and was answered in the negative; upon which
the order was given that the man should be instantly beheaded, lest the precious metals might
lose their value, should such a composition become generally known.
See
Nesbitt, Notes on the History of Glass-making (1871);
Blümner,
Technologie, iv. p. 379
(1887);
Deville,
Histoire de l'Art de la Verrerie (1873);
Fröhner,
La Verrerie Antique (1879);
Beckmann, History of
Inventions (1856); Marquardt and Mommsen,
Röm.
Alterthümer, vii. pp. 774 foll.
(1886).
