glass 
niat.-r i;il or imperfect ion in the manufacture, only slightly 
translucent. Ulass is an inorganic substance, as would 
naturally bu int'cnvd from its being the result of fusion, 
but some organic substances are called vitreous, borne 
rocks have a vitreous structure, like that of artificial glass, 
as, for instance, obsidian, which is often called mlcanic 
glass. (See obxiditin and lava.) The slags produced in fur- 
nace operations are vitreous substances, but usually only 
translucent, and not transparent, because the vitrification 
is Incomplete, and also because they are too deeply colored 
by metallic oxids. Glass, as the word is generally under 
stood, is an artificial product, and one of th most im- 
portant of manufactured articles. Its valuable qualities 
are : the ease with which it can be made to take any de- 
sired shape ; cheapness, the result of the small cost of the 
materials of which it is made; durability, and especially 
resistance to decomposition by acids and corrosive sub- 
stances generally ; transparency, a quality of the utmost 
importance, as evidenced by its use for windows and in 
optical and chemical instruments ; and the beautiful lus 
ter of those kinds which are used for ornamental purposes. 
Almost the only drawback to these good qualities of glass 
is its brittleness. The bases used in glass -manufacture 
are chiefly soda, potash, lime, alumina, and oxid of lead, 
and the quality of the article produced depends on the 
nature and amount of the basic material united with the 
silica. The combinations of silica with a simple alkaline 
base, either potash or soda, are soluble in water, and are 
known as water-gins^. (See soluble glass, below.) They 
are useful substances, but very different in their proper- 
ties from what is ordinarily known as glass. In addition 
to the alkaline base there must be an alkaline earth or a 
metallic oxid. The cheapest glass is that used for bot- 
tles; in this the basic material is chiefly lime, with some 
potash or soda, and alumina. Glass for medicine-bottles 
differs from ordinary bottle-glass in containing more pot- 
ash than the latter, and also in the greater purity of the 
material used. Window-glass usually contains both soda 
and lime: here absence of any tinge of color is impor- 
tant, except in the most inferior qualities. Potash and soda 
render the glass more fusible; alumina diminishes its 
fusibility; lime makes it harder; lead gives luster, fusi- 
bility, and high refractive power. Hence, in glass which 
is to be cut and polished, where beauty is of prime impor- 
tance, the base is chiefly oxid of lead, which amounts in 
some cases to half the weight of the material used. Glass 
in which lead is the essential base is called crystal orjlint- 
glas*. (See these words.) The finer kinds of glass with- 
out lead are called crown-glass. The tools employed by 
the glass-blower are simple, but require dexterity for 
their use. The process of manufacture depends on the 
fact that, at a very high temperature, glass is a liquid 
which can he readily cast ; at a full red heat it is soft, 
ductile, and easily welded ; when cold, it is hard and brit- 
tle. Glass to be serviceable must be annealed after the 
desired fonn has been given to it. This is done by heat- 
ing it nearly to the melting-point, and then allowing it to 
cool very slowly in an annealing-chamber. By the action 
of hydrofluoric acid, which combines readily with the 
silica in glass, etching can be done on a glass surface. 
When cold, glass can be ground or cut upon a wheel, 
scratched by a diamond-point (by which means sheets 
of glass are readily divided or shaped, as they will break 
easily along the lines of such scratches), cut and de- 
polished, or "ground" by a sand-blast, and brought to 
an exceedingly high polish. Specimens of Egyptian glass 
are in existence which can be dated back to about 2400 
B. C. ; in Egyptian sculptures of 4000 B. c. glass bottles 
are undoubtedly represented ; and among the bas-reliefs 
of Beni Hassan, about 2000 B. c., various operations of 
glass-blowing are portrayed. In historical Egyptian, Phe- 
nician, and Roman antiquity, glass was in familiar use. 
The great quantities 
of examples of an- 
cient glass vessels 
which have been ex- 
humed from tombs, 
etc. , form erly clear 
and transparent, are 
now as a rule charac- 
terized by a brilliant 
iridization like that 
of mother-of-pearl. 
This iridization is due 
". to the imperfect com- 
position of the glass, 
which has thus be- 
come affected by 
moisture during its 
stay under ground. Though well known to the Greeks, 
glass was in less common use among them, owing to the 
perfection of their ceramic ware. In Europe the most 
artistic manufactures of glass have been, since the middle 
ages, those of Venice, characterized by great elegance of 
form and lightness and thinness of substance, and those 
of Bohemia, of later date than the Venetian, and especial- 
ly notable not only for grace of form, but for enameling, 
cutting, and engraved decoration. 
They keep the wind out of their windows with glass, for 
it is there much used. Sir T. More, Utopia, II. 1L 2. 
I must be married to my brother's daughter, 
Or else my kingdom stands on brittle glass. 
Shak., Rich. III.,iv. 2. 
Cups 
Where nymph and god ran ever round in gold 
Others of glass as costly. Tennyson, Lover's Tale, iv. 
2. A plate, screen, vessel, instrument, etc., 
made of glass, (CT) A plate or pane of glass inserted 
in the frame of a window, picture, clock, hotbed, etc., to 
admit the light or permit a view, while excluding wind, 
rain, dust, or other interference. (6) A looking-glass; a 
mirror. It was formerly fashionable for ladies to carry a 
looking-glass hanging from the girdle. 
The glass of fashion, and the mould of form. 
Shak., Hamlet, iii. 1. 
Let all sweet ladies break their flattering glasses, 
And dress themselves in her. 
Webster, Duchess of Main, i. 2. 
We may see our future in the glasa of our past history. 
W. Phillips, Speeches, p. 374. 
Specimens of Ancient Roman Glass. 
(From " I-' Art pour Tous.") 
2530 
(c) A glass vessel filled with running sand for measuring 
time, called specifically an hvur-yta*s; hence, the time in 
which a glass is exhausted of its sand; specifically (/<"<".>, 
tin- time in which a half -hour glass is emptied of its sand. 
If you should omit to note those things at the end of 
euery foure glasses, I would not haue you to let it slip any 
longer time then to note it diligently at the end of euery 
watch, or eight glasses at the farthest. 
HakluyCs Voyage*, I. 436. 
Pro. What is the time o' the day? 
Ari, Past the mid season. 
/'*<. At least two glasses. Shak., Tempest, i. 2. 
She would not live 
The running of one glass. Shak., W. T., i. 2. 
(rf) A vessel made of glass: as, a jeMy-glass; aflnger-tyfcu*. 
Especially <<> A drinking- vessel made of glass; hence, 
the quantity which such a vessel holds, and figuratively 
what one drinks, especially strong drink : as, fond of his 
glass. 
The interview 
That swallow d so much treasure, and like a <jlas# 
Did break i' the rinsing. Shalt., Heu. VIII., i. 1. 
See that ye fill the gins* well up 
To the laird o' Warlestoun. 
Laird of Wartestoun (Child's Ballads, III. 111). 
Being you have abandoned yourself to my conduct, we 
will only call and drink a glass on horseback at the Talbot, 
and away. Cotton, in Walton's Angler, ii. 227. 
(/) An observing-instrument made of glass, or of which 
the main or most important part is of glass. (1) A lens ; 
a telescope; a field-glass. (2) A barometer. (3) A ther 
mometer. (4) An eye-glass: usually in the plural eye- 
glasses or spectacles. 
The moon, whose orb 
Through optic glass the Tuscan artist views. 
Hilton, P. L., i. 288. 
With glas* at eye, and catalogue in hand. 
Cowper, Task, vi. 288. 
Get me my glasses, Annie : thank God that I keep my eves. 
Tennyson, The Grandmother. 
Alabaster glass. See alabaster. Anaclastlc glass or 
vial. See atuiclastic. Argentine, black, blue, broad, 
bronzed glass. See the adjectives. Blar glass, orna- 
mental glassware made in the province of Alicante, Spain, 
especially that made in the sixteenth and seventeenth 
centuries. Bohemian glass, (a) Ornamental glassware 
made in Bohemia, famous 
since the sixteenth century 
for the richness of the colors 
employed in its enameled 
decoration, and especially 
for its incised or engraved 
ornament in delicate pat- 
terns. (M Glass having a 
lime base instead of a lead 
base, in this sense including 
nearly all the ornamental 
glassware, vessels, etc., of 
the best periods and styles, 
Venetian, Spanish, and oth- 
ers. (c) A kind of glass which 
is quite colorless, hard, dif- 
ficultly fusible, and less 
readily acted upon by chem- 
icals than any other kind of 
glass. Mirrors are often 
made of it, and it is largely 
used for the manufacture of 
chemical apparatus. It is 
made from ground quartz, 
purified potash, and lime. 
Cameo-glass, in Horn, antig., a kind of artistic glassware 
formed from glass consisting of superimposed layers of dif- 
ferent colors, the outermost of which was cut away so as to 
leave a design that appears in relief upon the layer under- 
n enth as a ground. Glassware of this 
kind, as originally produced by hand, 
is extremely costly from the difficulty 
of the cutting, but it is now imitated 
with comparative ease by machinery 
in the ware known as coxed glass. 
The universally admired specimens 
of Greco-Roman cameo-glass include 
the famous Portland vase of the 
British Museum, the Auldjo vase tn 
the same collection, and a beautiful 
amphora in the Museo Nazionale at 
Naples. In all these the design is in 
opaque white on a ground of dark, 
transparent blue, itself lined with 
opaque white. The same method 
was applied by the ancients to tab- 
lets or slabs, the interior lining of 
opaque white being sometimes 
omitted, and the ground being some- 
times in opaque blue, purple, or 
brown. In rare examples several 
colors are introduced. Canary 
glass, a bright-yellow glass colored 
by uranium oxid, having striking flu- 
orescent properties. Cased glass. 
Incised Bohemian Glass. Mu 
seum of Fine Arts, Boston. 
Nazionale, Naples. 
Seecases, i . Cast glass. Same as plate-ylatt. Claude 
glass. See Claude Lorrain inirror, under mirror. Col- 
ored glass, glass which is colored in the pot, whereas 
enameled glass is made by firing vitriflable colors on a 
transparent or other ground. Compare flatbed glass. 
Compressed glass, glass which is tempered by being 
cast or pressed in chilled molds, a process perfected by 
Siemens of Dresden. It has a fibrous fracture, may he 
bored and polished by the wheel, and is believed to be 
stronger than glass tempered in oil, as in the Bastie 
process. E. H. Knight. Covered or coated glass, 
glass prepared for stained-glass work, etc. , by being coated 
with color on one side; flashed glass. Nearly all the 
ruby glass used in windows, etc., is of this character. 
Cryolite glass. See m/olitr. Cut glass, flint-glass 
shaped or ornamented by cutting or grinding with polish- 
ing-wheels. The surface is commonly cut into grooves, 
so arranged as to leave prismatic and crystal-like projec- 
tions between them. The work is done by rapidly revolv 
glass 
ing wheels of stone, iron, or wood, to the periphery of 
which sand, emery, and polish ing -powder are applied. - 
Devitrlfied glass, glass which has been exposed to a 
great heat and in ibis way rendered opaque and hard, 
.M>mr\vh;i! n-.irnibliiig porcelain. The process involves 
a partial crystallization of the previously amorphous 
mass. Diamond-cut glass, thick glass which has beeu 
cut into V-shaped grooves or channels crossing one an- 
other at an angle, and leaving pyramid-shaped projec- 
tions: a common form of ornament on cut glass. Dia- 
mond-molded glass, molded or cast glass made to imi- 
tate the diamond-cut glass. Doubled glass, a glass 
made of two or more colors superposed; flashed glass. 
Enameled glass, glass which has been decorated 
with vitrifiable pigments, or painted according to the 
enamel method. Sec fffcM*jwftffll0. Erecting glass. 
.Same as erector, 1 (b). Filigree glass, tieujiliyrre-glas*. 
- Flashed glass. Set- /ta^/U. Franklin glasses, spec- 
tacles the lenses of which are divided horizontally, each 
having different powers above and below. Glass-melt- 
ing pot, the vessel for melting the frit in glass-factories, 
made of refractory clay mixed with the ground substance of 
old pots. Glass of antimony, a vitreous oxid of anti- 
mony mixed with stilphid. Glass of borax, a vitreous 
transparent substance obtained by exposing to heat the 
crystals of biborate of sodium. Glass of cobalt. See 
coba If. Granulated glass, glass the surface of which is 
raised in slight projections like grains of sand, used for or- 
namental vessels. Ground glass, any glass that has been 
depolished by a sand-blast, by grinding, or by etching with 
acids, so as to break up light transmitted through it, and 
destroy ita transparency. Half-minute glass, a sand- 
glass used on shipboard to mark the time in heaving the 
log. See log. Hardened glass, tempered or toughened 
glass. Heavy glass, a technical name formerly given to 
English flint glass. Kelp glass, glut* of which the alka- 
line ingredient soda is furnished by kelp. This process is 
now almost wholly abandoned. Klnkled glass, glass 
the surface of which is raised in small rounded elevations 
produced by blowing the glass into a mold formed of a 
more or less fine netting of wire. Ladled glass. Same 
as culletl. Madrepore glass, a kind of glass in which 
star-like opaque colored patterns are crowded together in 
a transparent mass of glass. It is a variety of milleflori 
glass. See moxaic glass. Marbleized glass, a glass 
which, while hot, has been immersed in water, then re- 
heated and expanded by blowing. The incipient fractures 
become reunited, but show in the finished object like veins 
in marble. /-,'. //. Kniyht. Hatted glass, glass orna- 
mented by means of certain white or colored mineral pow- 
ders, applied to the entire surface of the object, and then, 
in some cases, removed from those parts which are to 
appear as a dull ground. The glass is then fired, and the 
composition, which is very fusible, becomes fixed, the re- 
sult oeing a bright pattern on aground resembling ground 
glass. Metallized glass, an ornamental glass with Hakes 
of gold, mica, platinum, etc., scattered through it. Milk- 
glass. Same as crj/olite glass. Milleflori glass lit. 
mille, a thousand, -f fiore, a flower), ornamental glasswork 
made by fusing together tubes or rods of glass enamel 
(which see, under enamel) of different colors, or pieces 
of filigree. The fused mass is cut into sections, which 
appear as ornamental figures of varied design, and are 
embedded in white transparent glass to form paper- 
weights and objects of like character. Mosaic glass, 
glass in which a number of pieces of different colors are 
fused together to form one mass. This Is commonly 
done by means of glass rods, which are laid together 
sidewise, and after being united in one mass can then 
be cut across, producing a varied pattern at each sec- 
tion; these compound bars can be reheated and pulled 
out to any degree of tenuity, retaining the pattern at 
the cross-section on a smaller scale. Such rods are cut 
into slices for making millefiori glass, etc. Muller'S 
glass. Same as hyalite. Multiplying glass, a toy con- 
sisting of a convex glass or lens cut with numerous facets, 
the effect of which is to repeat the image of the object 
observed as many times as there are facets. Murano 
glass, glass made at Murano, near Venice. The greater 
part of the glass 
called Venetian 
has always been 
produced there, 
and all the modern 
Venetian glass- 
works are there, 
Musical glasses, 
(a) A musical in- 
strument consist- 
ing of graduated 
strips of glass 
mounted on a reso- 
nance-box, so as to 
be played upon by 
hammers. (b) A 
musical instru- 
ment consisting 
either of glass 
tubes or glass 
bowls, graduated 
in size, which can 
be played by the friction of the moistened finger. Also 
called gla$s harmonica. Ondoyant glass [F. ondoj/ant, 
ppr. otondoyer, wave, undulate], a modern glass with an 
uneven waved surface, made in all tints, used in colored 
windows to imitate the subtle play and variation of light 
and color forming one of the characteristic beauties of 
medieval artistic glass. Opalescent glass, glass hav- 
ing a changeableness of color somewhat like that of the 
opal, showing cloudy-blue, orange red, and intermediate 
colors, according to the light in which it is viewed. Op- 
tical glass, a flint-glass used in the manufacture of op- 
tical instruments. It contains a large proportion of lead, 
and hence is of great density. Painted glass, glass or- 
namented by painting in vitriflable pigments or enamels: 
often colloquially used to include colored or stained glass, 
and compositions in such glass. See def. 1. 
Far more important than the introduction of the pointed 
arch was the invention of painted glas*, which is really the 
important formative principle of Gothic architecture; so 
much so, that there would be more meaning in the name, 
if it were called the ''painted glass style," instead of the 
pointed-arch style. J. Fergvswn, Hist. Arch. I. 526. 
Examples of Murano (Venetian) Glass, i6th 
century. ', From " L'Art pour Tous.") 
