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from the melting-pot, certain colouring ingredients are 
to be mixed with the materials of the white glafs in 
fufion, which forms the bafis; and this bafis muft be 
cleanfed or purified, and rendered hard or ductile, in 
proportion as tlie coloured glafs is required for cheap 
and common purpofes, or for choice and coftiy wares, 
or the imitation of pellucid gems. In the firft cafe, the 
cheapeft colouring matters are employed, as iron or 
manganefe, witii which the glafs beads and rofaries, fo 
much in ufe in Roman-catholic countries, are chiefly 
coloured. But when rich and brilliant colours are to 
be produced, not only the choicell and molt durable 
pigments are to be chofen, but the bafis or melted glafs 
mult likevvife he pure, and adapted to the reception of 
the colours whicli is intended to be given. For this 
juirpofe the two following compofitions are recom¬ 
mended. I. Take twelve pounds of the finefi white 
filiceous fand, walh and cleanfe it thoroughly; then 
add feven pounds of pot-alli, one pound of I’altpetre, and 
half a pound of borax : levigate, and mix them well 
togetlier; and when committed to the melting-pot, a 
fine hard white glafs bafis will be formed. 2. Take 
twelve pounds of the fame white filiceous fand equally 
cleanfed, feven pounds of pot-afli purified with falt- 
petre, one pound of nitre, half a pound of borax, and 
four ounces of white ari'enic : levigate, mix, and melt, 
as befoie, and a pure white glafs bafis will be formed, 
conliderably fofter or more duftile than the firft. 
The prefent methods _Gf imparting colours to glafs, 
are as follow : 
B LA c K.—To give a deep and fine black to glafs, take 
of cryftalline and pulverine frit, of each twenty pounds; 
of calx of lead and tin four pounds; fet all together in 
a pot in the furnace, well heated ; when the glafs is 
formed and pure, take fteel well calcined and powdered, 
fcales of iron that fly off from the fmith’s anvil, of each 
an equal quantity ; levigate and mix them well; then 
put fix ounces of this powder to either of the above- 
deferibed bales while in fufion; mix, and let tliem boil 
ftrongly together; then let it ftand in fufion twelve hours 
to purify, and after this w ork it. It will be a moft ele¬ 
gant velvet black. 
B LU E.— A full blue may be given by adding fix drams 
of zaft'er, and two drams of manganefe, to ten pounds of 
either of the compofitions deferibed above. For a very 
pure blue, half an ounce of calcined copper may be 
iifed inftead of the manganefe, and the proportion of 
zafter diminiftied to one half. Glafs refembling fapphire 
may be made with ten pounds of the pure wiiite glafs 
in fufion, three drams of zafter, and one dram of the 
calx cqffii, or precipitation of gold by tin. Orafapphire- 
coloured glais may be made by mixing with the glafs in 
fufionone-eigltth ofitsw’eight of finalt. A beautiful blue 
may alfo be produced from the calx of regulus of cobalt. 
Garnet Red. —Take equal quantities of cryftal and 
rochetta frit for the fufed glafs; and to every hundred¬ 
weight of this mixture add a pound of manganefe and 
an ounce of prepared zalfer : tfiefe are to be powdered 
feparately, then mixed and added by degrees to the frit 
while in the furnace. Great care nuift be taken to mix 
the manganele and zafi'er very perfettly ; and when the 
matter has flood twenty-four hours in fufion, it may be 
worked. Glafs of this colour may alfo be made by 
adding one pound of glafs of antimony, due dram of 
manganele, and the fame quantity of the precipitate of 
gold by tin, to two pounds of either of the compolitions 
or bafes above deferibed. 
Gold Yellow.— This colour may be produced by 
taking ten pounds of the compofitions for hard glafs, 
and for every pound of liich bafis adding two ounces of 
calcined borax, ten ounces of red tartar of the deepeft 
colour, tw o ounces of magnefia, and two drams of char- 
co.al. Precipitates of filver baked on glafs will alfo ftain 
it yellow, and likewife give a yellow colour on being 
mixed and n\cUed with fifty times their weight of the 
ASS. C03 
vitreous compofition: the precipitate from aquafortis 
by fixed alkali feems to anfvver belt. Yellow glafs may 
likewife be obtained with Pruflian blue, or witli anti¬ 
mony and lead. Equal parts of the glafs of antimony, 
of flint calcined and levigated, and of minium, produce 
a glafs of a bright yellow ; and with two parts of glafs 
of antimony, two X)f minium, and three of powdered 
flint, the colour approaches more to that of gold. 
Green. —This colour may be imparted to glafs by 
adding three ounces of copper precipitated from aqua¬ 
fortis, and two drams of precipitated iron to nine pounds 
of either the compofitions above recommended. 'I'o 
give an enierald-green, take five pounds of cryftalline 
metal that has been palled feveral times through water, 
and the fame quantity of the common white metal of 
polverine, four pounds o,f pol verine frit, and three pounds 
ot red lead; mix the red lead well with the frit, and 
put all into a'pot in the furnace. In a few hours tlie 
mals will be purified; then call the whole into water, 
and feparate the lead; return the metal into the pot, 
and let it ftand a day longer in fufion; then pul in tli-e 
powder of the refiduum of the vitriol of copper, and a 
little crocus martis; and there will be produced a moft 
lively green, little inferior to that of the oriental eme¬ 
rald. For a fea-green,' the fineft cryftalline glals only 
mull be ufed, and no manganefe mult be added at firft 
to the metal. The cryftal frit mull be melted alone; 
and the fait, which fwims like oil on its top, mull be 
feummed off very carefully. Then to a pot of twenty 
pounds of this metal add fix ounces of calcined brafs, 
and a fourth part of the quantity of powdered zaft'er : 
this powder mull be well mixed, and put into tlie glafs 
at three times; it will make the metal fwell at firft, but 
all mull be thoroughly mixed in the pot. After it has 
ftood in fufion three hours, take out a little for a proof: 
if it be too pale, add more of the powder. Twenty-four 
hours after the mixing the powder, the whole will be 
ready to work. 
Purple. —This colour maybe produced iTy adding 
to ten pounds of pure white cryftal glafs, as a balls, fix 
drams of zafter, and one dram of gold precipitated by 
tin ; or to the lame bafe, one ounce of manganele and 
half an ounce of zaffer. The colour of ainethyll may 
alfo be imitated in this way. 
Ruc Y Red.—C alcine in earthen velTels gold diffolved 
in nitro-muriatic acid ; the menllruum being evaporated, 
by dillillation, more aqua-regia mull be added, and the 
abllradtion repeated five or fix times, till it becomes a 
red powder. This operation will require many days in 
a hot furnace. When the powder is of a proper colour,, 
take it out, and melt the fineft cryftal glafs, and purify 
it by often calling it into water; then add, by Imall 
quantities, enough of this red powder to give it the 
true colour of the ruby, with au elegant and perfect 
tranfparence. 
Of painting on GLA.SS.. 
The ancient manner of painting on glals was very fim-^ 
pie : it conlilled in the mere arrangement of pieces ot 
glafs of different colours in lome lort of lymmeiry, and' 
conftituted what is now culled rnojaic work. In procels 
of time, however,^ they came to attempt more regular 
defigns, and alio, to reprefent figures heightened with 
all their lhades : yet they proceeded no farther than tlie 
contours of the figures in black with water-colours, and 
hatching tlie draperies after the lame manner on glalles 
ef the colour of the objedt they deligned to paint, for 
|he carnation, they tiled glals of a bright red colour; 
and upon this they drew the principal lineaments, or 
outline, with black. At length, the talle for this loit 
of painting improving conliderably, and the art being 
found applicable to the adorning of churches, halls, &c. 
they found out means of incorporating the colours moft 
beautifully in the glafs itlelf, by heating them in the 
fire to a proper degree ; having firft laid on the colours. 
^ 4, A Frcncn 
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