DOI Page / Citation link:
https://doi.org/10.11588/diglit.36284#0050
42
and colour,—between the fully-covered ground and the
broken ground, between the larger elements of design, and
the more delicate minute work.
The perfect taste inherent in the decorations of the old
Oriental gilt and enamelled glass-work, and not its laborious
technical completeness, enables every one who looks at
most of those artistic creations of the Muhammadan East,
to realise the sense of satisfaction and delight in beauty.
CHEMICAL ANALYSIS
c/ ^Av w,a.s\s, cmd ?Ae decorao/*
?Ae of aw o/J AraA ^a.s.s recced, a^AA'A cawe ^roAaAJy
y?-o?w dte dsosywe of //a,saw m Casro dah/a? ysom
/Ac ac/dd/e of die /bardew^A cew^wry.
The article to be tested—a crescent-shaped fragment,
about 150 mm. in breadth and 55 in height, manifestly part
of a mosque-lamp or vase—has on both sides, upon
undecorated fields within round borders, the molten
settings of handles; the remainder of the surface is
decorated with polychrome ornament in relief-enamel, placed
within red outlines, in free, careless, and unelaborate work.
The enamel layers have spread sometimes over the
outline, in other places they do not exactly reach it, and
in some others still, they seem formless, having merely the
character of spots of colour.
The enamels, as well as the outlines, lie partly upon
gold—which we know to be a characteristic of Arabic
enamelled glass.
Cold ornaments once undoubtedly covered the whole
vessel between the colour-decorations, and occupied the
handle-fields, and perhaps there was gold on the handles
themselves; but it has been corroded by the lapse of ages,
and has disappeared. Traces of the former gilding, besides
those which lie under the enamel, and appear in irregular
dots in connexion with the enamel-ornament, may also
be found here and there on the empty surface with the
aid of the microscope. Even in little clots and hollows
under the welded handles, atoms of gold are lodged. The
glass surface, in all the spots on which gold was used,
appears dull, and of a quality quite distinct from that
of the places which were not gilt. This can be noticed
from the inside of the glass which allows the whole surface
to be observed.
The relief enamels of the ornament are, even to the
white and the red, half-transparent. Blue, in the colour
of the lapis lazuli, is richly handled ; iron-red is used in
a much lesser degree ; while the other colours, clear green,
clear yellow, and white, are employed on small surfaces.
The glass substance of the vessel and the handles, is
badly clarified, and dotted with clots and with great and
little bubbles; it is not purely white, but of distinctly
brownish-green colour.
The analysis of the glass-mass gave the following
results :—
I II
Silicious earth
SiO
68-73 7.
...
Lime ....
CaO
8-62 7.
...
Magnesia
MgO
4-157.
...
Kali ....
K,0
2-87 7.
...
Natron ....
Na^O
12-547.
...
Potter's earth
A1,0,
1-69 7.
I-687.
Peroxide of iron .
FeA
0-47 7.
0-50 7.
Protoxide of Manganese
MnO
0-74 7.
99-81
0-697.
Striking, and even unique in the numerous analyses
of old and new hollow glasses known to me in the
literature of the subject,—is the high proportion of
magnesia in the fragment, derived from dolomite lime-
stone used in the manufacture of the glass. Magnesia, as
well as dolomite lime-stone, is regarded in the foundries as
a detrimental substance to be avoided. It densely fluidises
the glass-mass which thereby becomes difficult to clarify.
From the above analysis, the molecular formula of the
glass is calculated as 0'9 RgO : 1 RO : 4*45 SiO; in which,
under R„0, the alkalies, and under RO the alkaloid earths,
are put together.
Of other examples of tested glass, capable of resisting
atmospheric influence, the combination runs thus —
0*9 R„0 : 1 RO : 5 to 5'4 SiO^. The glass of the specimen
appears then to be poor in silicious earth, which is a necessary
result of the use of the magnesia-holding lime-stone,
as with a higher sand capacity, the mass would be far
too densely fluid.
Further remarkable is the proportionate relation of
alkalies to lime (in this case, magnesia-bearing lime), for the
purpose of affording a fitness to resist atmospheric influence
(the injurious action of bad weather) ; which appears here
precisely as the best known proportion of our own time.
With the enamels, by reason of their small quantity,
only qualitative investigations could be set on foot, as to
colour-bodies, and their possible holding of lead. To this
the blue enamel offered an exception of very special
interest. The single enamels were rubbed off with the
diamond point, aided by a few drops of water, and poured
into a dish of platinum. Then they were exposed to
analysis, and the result was as follows—
Red : Lead glass coloured by oxide of iron.
Green : „ „ oxide of copper.
Yellow : ,, ,, antimonic acid.
White : ,, colour-body not ascertainable.
That would correspond with the synthesis of the
glass-enamels known to-day.
and colour,—between the fully-covered ground and the
broken ground, between the larger elements of design, and
the more delicate minute work.
The perfect taste inherent in the decorations of the old
Oriental gilt and enamelled glass-work, and not its laborious
technical completeness, enables every one who looks at
most of those artistic creations of the Muhammadan East,
to realise the sense of satisfaction and delight in beauty.
CHEMICAL ANALYSIS
c/ ^Av w,a.s\s, cmd ?Ae decorao/*
?Ae of aw o/J AraA ^a.s.s recced, a^AA'A cawe ^roAaAJy
y?-o?w dte dsosywe of //a,saw m Casro dah/a? ysom
/Ac ac/dd/e of die /bardew^A cew^wry.
The article to be tested—a crescent-shaped fragment,
about 150 mm. in breadth and 55 in height, manifestly part
of a mosque-lamp or vase—has on both sides, upon
undecorated fields within round borders, the molten
settings of handles; the remainder of the surface is
decorated with polychrome ornament in relief-enamel, placed
within red outlines, in free, careless, and unelaborate work.
The enamel layers have spread sometimes over the
outline, in other places they do not exactly reach it, and
in some others still, they seem formless, having merely the
character of spots of colour.
The enamels, as well as the outlines, lie partly upon
gold—which we know to be a characteristic of Arabic
enamelled glass.
Cold ornaments once undoubtedly covered the whole
vessel between the colour-decorations, and occupied the
handle-fields, and perhaps there was gold on the handles
themselves; but it has been corroded by the lapse of ages,
and has disappeared. Traces of the former gilding, besides
those which lie under the enamel, and appear in irregular
dots in connexion with the enamel-ornament, may also
be found here and there on the empty surface with the
aid of the microscope. Even in little clots and hollows
under the welded handles, atoms of gold are lodged. The
glass surface, in all the spots on which gold was used,
appears dull, and of a quality quite distinct from that
of the places which were not gilt. This can be noticed
from the inside of the glass which allows the whole surface
to be observed.
The relief enamels of the ornament are, even to the
white and the red, half-transparent. Blue, in the colour
of the lapis lazuli, is richly handled ; iron-red is used in
a much lesser degree ; while the other colours, clear green,
clear yellow, and white, are employed on small surfaces.
The glass substance of the vessel and the handles, is
badly clarified, and dotted with clots and with great and
little bubbles; it is not purely white, but of distinctly
brownish-green colour.
The analysis of the glass-mass gave the following
results :—
I II
Silicious earth
SiO
68-73 7.
...
Lime ....
CaO
8-62 7.
...
Magnesia
MgO
4-157.
...
Kali ....
K,0
2-87 7.
...
Natron ....
Na^O
12-547.
...
Potter's earth
A1,0,
1-69 7.
I-687.
Peroxide of iron .
FeA
0-47 7.
0-50 7.
Protoxide of Manganese
MnO
0-74 7.
99-81
0-697.
Striking, and even unique in the numerous analyses
of old and new hollow glasses known to me in the
literature of the subject,—is the high proportion of
magnesia in the fragment, derived from dolomite lime-
stone used in the manufacture of the glass. Magnesia, as
well as dolomite lime-stone, is regarded in the foundries as
a detrimental substance to be avoided. It densely fluidises
the glass-mass which thereby becomes difficult to clarify.
From the above analysis, the molecular formula of the
glass is calculated as 0'9 RgO : 1 RO : 4*45 SiO; in which,
under R„0, the alkalies, and under RO the alkaloid earths,
are put together.
Of other examples of tested glass, capable of resisting
atmospheric influence, the combination runs thus —
0*9 R„0 : 1 RO : 5 to 5'4 SiO^. The glass of the specimen
appears then to be poor in silicious earth, which is a necessary
result of the use of the magnesia-holding lime-stone,
as with a higher sand capacity, the mass would be far
too densely fluid.
Further remarkable is the proportionate relation of
alkalies to lime (in this case, magnesia-bearing lime), for the
purpose of affording a fitness to resist atmospheric influence
(the injurious action of bad weather) ; which appears here
precisely as the best known proportion of our own time.
With the enamels, by reason of their small quantity,
only qualitative investigations could be set on foot, as to
colour-bodies, and their possible holding of lead. To this
the blue enamel offered an exception of very special
interest. The single enamels were rubbed off with the
diamond point, aided by a few drops of water, and poured
into a dish of platinum. Then they were exposed to
analysis, and the result was as follows—
Red : Lead glass coloured by oxide of iron.
Green : „ „ oxide of copper.
Yellow : ,, ,, antimonic acid.
White : ,, colour-body not ascertainable.
That would correspond with the synthesis of the
glass-enamels known to-day.