or rather stain the glass, 
redtly-for burning, to fix the colours, 
by the preparations which have 
been laid upon it. The furnace most proper for the 
er is similar to that used by assayers or enamel- 
rs. It consists of a muffle, or arch of fire clay or 
, 8o placed over a fire-place, and surrounded by 
nel to receive a very considerable heat, but in tl. 
‘most equable and regular manner throughout the whole; 
for if this is not attended to, some parts of the glass 
will become too much stained, before the colour takes 
place in others. The mouth of the mufile, and the en- 
ry to the fire through which the fuel is supplied, should 
+s hes opposite sides, to prevent as much as possible the 
ar Mg dust into the muffle; and the mouth of the 
m should be closed by iron folding-doors, with 
small openings or peep holes through them, to allow 
the artist to SSiarve the rogress of the burning, by 
y withdrawing small trial slips of glass, which are stained 
with the principal tints employed in the picture. © 
Sg ap cerhr got of very. goo fire clay, flat 
at the’ bottom, and only five or six inches high, being” 
so much arched at the top as is necessary to render the 
roof strong, and resist falling in by its weight when heat- 
ed; the muffle must be so close on all sides, as to admit 
no smoke or flame. Before the plate of glass is intro- 
duced into the furnace, a bed is prepared upon the bot-_ 
tom'of the muffle. For this purpose, lime is used. It 
must be iously burned, so as to yield no more gas, 
and then reduced to a fine powder. In this state, the 
bottom of the muffle is strewed half an inch deep, and 
levelled with a feather. The glass is then introduced, 
and sometimes the muffle is filled up with other glasses 
. laid above the first, having beds of lime between each. 
The fire is lighted after all is shut up close, and the heat 
is raised very —— at first, lest the glass should be 
broken by it; but after the fire has attained its full heat, 
it is continued for three or four hours, more or less, ac- 
cording to the ces observed upon the trial slips 
of glass, which are withdrawn for that purpose ; and 
the yellow colour is principally attended ‘to, as that is 
found the best test for the others. The operation of 
= ga Sa thus finished, the fire is extinguished, or 
rather to die away, and the heat to subside gra- 
amar to prevent the glass becoming brittle, as it 
‘do without this precaution; for the heat when 
at the greatest, must be sufficient to make the glass very 
flexible, as is seen by the trial glasses. 
We shall conclude this Section with the preparations 
for a few principal colours, =~ xt 
Preparation for staining glass of a flesh colour.—Take 
one ounce of minium, and two ounces of red enamel, of 
that kind which is called Venetian glass enamel ; pound 
them to a fine a and grind it with brandy upon 
a hard stone. is mixture, when slightly baked, will] 
produce a fine flesh colour. 
‘Black colour.—Take 14% ounces of those scales of 
iron, which are found round the anvil of a smith’s shop; 
mix with it two ounces of white glass, an ounce of an- 
timony, and half an ounce’ of m ese; pound and 
ind them with strong vinegar. Brilliant 
may also be obtained, by a mixture of blue with 
the oxides of manganese and iron. 
Another black colour.—Take equal of iron scales 
and of small beads or ents of» 3 pound them 
exceedingly fine, and grind them to a consistence to 
work with a pencil. 
Another black is made from three parts of glass of 
lead, two parts of the scales of copper, and one of anti- 
wa” treated as before. 
brown.—-Take one ounce of white glass or enamel 
GLASS. 
317 
and half an ounce of good munganese ; grind them first § 
very fine with vinegar, and afterwards with brandy. 
d, rose, and brown colours, are made from red oxi- yy na of 
dated iron prepared with nitric acid, Their flux is com- ,, 
posed of borax, sand, and minium, in small quantity. 
For red.—Take one ounce of red chalk pounded, and 
mix it with two ounces of white hard enamel, and a 
small proportion of the scales of which fall off 
when it is much heated in a forge. —— — 
ve red, but requires trial if it will support 
fire’ oot not, pit rem of the scales of copher. 
For another red.—-Take one part of red chalk, which 
is too hard to write with, one part of white enamel, and 
a fourth of orpiment ; grind therm together with vinegar. 
This is a strong poison. 
Or a red may be composed of rust of iron, glass of 
antimony, and yellow glass of lead, such as is used by 
potters, these hie in equal uantities ; to which add 
a little silver, calcined with sulphur. This composition 
‘ound fine, produces a very fine red colour on glass. 
When the oxide of copper is used to stain glass, it as- 
sumes a bright red or a green colour, according as the 
glass is more or less heated in the furnace. 
Bistres and brown reds may be obtained, by mixtures 
of different proportions of manganese, brown oxide of 
copper, and the oxide of iron called umber. They are 
previously fused with their solvents. 
For green.—Take two ounces of brass burned. until 
it becomes a calx, two ounces of minium, and eight 
ounces of fine white sand ; reduce them to a fine pow- 
der, which inclose in a well luted ‘crucible, heated in an 
air furnace with a strong fire for’ an hour. When this 
mixture is cold, pound and grind it ina brass mortar. 
Green may often be advantageously obtained, by a yel+ 
low on one side, and a pale blue on the other. 
For a fine yellow colour—Take fine silver in thin 
plates, and dissolve it in nitrous acid, and precipitate it ; 
mix the precipitate with three times the quantity of pi 
clay, well burnt, and pounded. With this the back of 
the glass must be painted, or it will run into the other 
colours. 
Another yellow can be made by melting silver in a 
crucible, and whilst in a state of fusion throw into it 
powdered sulphur in small quantities, and stir it up 
until the silver is reduced te a ealx. Grind this upon 
a stene, and mix with it as much antimony a: the silver, 
and some yellow ochre; which has been previously cal- 
cined in a crucible, until it is changed to a red brown 
colour. Work all these together with urine, and paint 
it on the back of the glass. 
Another yellow.—Cut thin plates of silver into small 
pieces, and put them into a crucible with sulphur and 
antimony. When melted, throw out the contents into 
clear water, and afterwards pound and grind the prepa- 
ration, so that it will work-with a pencil. — 
A pale yellow,—Fill a crucible with thin plates of 
brass, with beds of sulphur and antimony in der. 
Burn it till it ceases to smoke, and throw it hot into wa- 
ter. Reduce this to fine powder, and having added six 
times as much yellow ochré burnt, mix it with vin % 
A fine yellow, equal in beauty to that of the ancient 
painters, has been discovered by M. Meraud. He em- 
ploys muriate of silver, oxide of zine, white clay, and 
the yellow oxide of iron. These coleurs are applied ta 
the glass simply ground, and without flux. 
Blue colour,—Take mountain blue, and beads of glass, 
equal portions ; grind them whilst dry to an impalpable 
powder, and proceed as with the others. 
In general, the same colours as are used for painting 
on porcelain, and many of those used-in enamel 'paint- 
