Year: 1879

1t is not generally known, that the beau
tlful vases and other forms of iridescent
glass, which have recently begun to adorn
tho windows of our chinawarc dealers, mark
the revival of one OF the lost arts of old Ro-
man days. Most of the old glass brought
to light from the buried cities of Pompeii
and I1crculancun, from Roman tombs, and
more recently from the treasures of the
Cypriotc cities or temples, possesses this
curious property of iridcsccncc, by means
Of which it reflects light with all the colors
of the rainbow. There has been some dis
pute as to whether this glass was iridcsccnt
when made, or whether it acquired this
quality subsequently by some natural
agency. The more reasonable conclusion,
and the one adapted by Mr.. Poligot, tho
celebrated French chemist, Is that the glass
originally plain, became iridcscent from
long exposure to the action of the air and
moisture at q high temperature, these con-
ditlons being admirably fulfilled in the old
Roman tombs, where most Of the glass is
found. All glass has tendency to be-
como iridescent under certain conditions !;
but in some kinds this tendency is more
strongly marked than in others. In glass
for optical Instruments a tendency to be-
come iridescent Is serious fault and differ
cnt kinds of glass arc combined to form
perfect colorless lens. Modern chemists
and glassmakers have long been trying to
discover tho art of making glass iridescont
by some more speedy means than that of
burying it in damp soil for the benefit of
thanklcss posterity. With all the pro-
gress made in kindred branches OF the art,
nothing of note was done in this direction
until Two French chemists quite recently
succeeded in artifcially producing this
lridcscence. Tho process they make use
of Is said to consist essentially in submitting
the glass, under a considerable pressure, and
at an elevated temperature, to tho action of
water containing fifteen per cent. of hydro
chloric acid. Only certain kinds OF glass
arc suitable for this operation. Tho action
Of this acid Is thought to be analogous to
that Of the elements upon the older glass in
dissolving the alkaline siicates and leaving
the surface Of the glass finely ridged or cor
rugatcd and thus capable of refracting the
lights with prismatic or rainbow colors like
those of mothcr-ot-pearl. The modern glass
stands any amount of rubbing or cleaning
without losing Its curious property but, if
the exposed surface be cut or ground of,
the iridescent effect Is instantly lost, show
ing that Its cause ls merely superficial and
not structural, as Is the case with mother
of-pcarl. The Bohemian glass, so far, seems
to be the favorite for embellishing with the
new iridescencc. Bohemian glass will re.
sist q much greater heat than any other
kind, and is made in graceful shapes, and
Is clear and transparent. At present the
leading Bohemian factory Is producing
good deal of this iridescent glassware, prin-
cipally for the European market, as the
American public Is hardly yet acquainted
With this novel and beautiful glassware.
Ono Of the greatest charms Of this new glass
is it's infinite variety and freshness. No
two pieces are alike in color, and no piece
remains the Same when placed In now
position or regarded from a different point
of view. All show q greater or smaller
range of the spectrum, curve or bent, ac-
cording to the shape of the glass but while
some pieces flash with red and yellow, 9TH
ers arc tender, with sllvery blue or rich
gold gray, and still othors exhibit oil the
colors OF the rainbow.