21)4 G E 
ferved. 5. Tliat the materials be all well mixed ; and, 
if not fufficiently baked the firft time, to be committed 
to the fire again, without breaking the pot: for if tliis 
be not obferved, they will be full of blifters and air- 
bladders.—To render the pafte as hard as pofiible, and 
capable of retaining the utmoft durability and beauty : 
Take of prepared cryftal ten pounds ; fait of polverine 
fix pounds ; fulplrur of lead two pounds : mix thele 
well together into a fine powder ; make the whole with 
pure water into a hard pafte ; and make this pafte into 
fmall cakes of about three ounces weight eacli, with a 
hole in their middle; dry them in the fun, and after¬ 
wards calcine them in a potter’s furnace. After this, 
levigate them to a perfedl finenefs on a porphyry ftone, 
and fet this powder in pots in a glafs-furnace to purify 
for three-days ; then caft the whole into water, and af- 
ferv/ards return it into the furnace, w'here let it lland 
fifteen clays, in which time all foulnefs will difappear, 
-and the pafte wdll gieatly refemble the natural jewels. 
To give this the colour of the emerald, add to it brafs 
thrice calcined; fora fea-green, brafs fimply calcined 
to a rcdnel's ; for a fapphire, add zafter, with manga- 
nele ; and for a topaz, manganefe -and tartar. All the 
gems are imitated in the fame way of working as tlie 
making of cdloured glaftes ; the bafes for which are lb 
hard, that they very much approach the natural gems. 
The colours of all the gems made of the feveral 
paftes, (liould be deeper or lighter, accorcling to the 
work tor which tl;e ftones are defigned ; and it is to be 
obferved that I'mall ftones for rings, &c. require a deeper 
colour, and large ones a paler. Belides the colours 
made from manganefe, verdegris, and zafter, which are 
the ingredients I'noft commonly ufed, there are feveral 
fupierior ones which care and Iklll may often fabricate. 
Very fine red may be made from gold, and one not much 
inferior from iron ; a very fine green from brafs or cop¬ 
per ; a ficy-colour from filver, and a much finer one 
from the granite of Bohemia. 
Another miuch-approved method of making pafte for 
coloured gems, is this; Take a quantity of faccharum 
faturni, or fugarof lead, made with vinegar in the com¬ 
mon w'ay ; fet it in fand, in a glafs veflel well luted 
from the neck downwards ; leave the mouth of the 
veflel open, and continue the fire twenty-four hours; 
then take out the fait, and if it be not red, but yellow, 
illi, powder it fine, and return it into the veffel, and keep 
3 t in the land-heat twenty-four hours more, till it be¬ 
comes of the colour of red cinnabar. The fire mull 
not be fo ftrong as to melt it, for then the procefs would 
be fpoiled. Pour diftilled vinegar on this calcined fait, 
and feparate the folution from the dregs ; let the de¬ 
canted liquor Hand fix days in an earthen veffel, to give 
time for the finer fediment to fubfide ; filter the liquor, 
and evaporate it in a glafs yelfel, and there will remain 
a pure lalt ot lead ; dry this well, then dilfolve it in 
lair water; let the folution Hand fix days in a glazed 
pan; let it lubfide, then filtre the clear folution, and 
fvapor.ite it to a yet more pure fait ; repeat this ope¬ 
ration three times; put the now perfeclly pure lalt into 
a glals veffel, fet it into a land-heat -for feveral days, 
and it will be calcined to a fine impalpable powder, of 
a lively I'ed. This is the true fulpliur of lead. —Take all 
the other ingredients as in the common compolition of 
the piftes of the feveral colours, only inllead of red 
lead, life this powder ; which will well reward the trou „ 
hie of the operation. 
A pafte or bafis proper for receiving colours may alio 
be luadc by wcli-pounding and mixing fix pounds of 
white land cleanfed, three pounds of red lead, two 
pounds ol purified pearl-alli, and one pound of nitre. 
V fofter pafte may be made in the fame manner, of fix 
jiounds of white fand cleanfed ; red lead, and purified 
pearl-afii, of each three pounds; one pound of nitre, 
half a pound of borax, and three ounces of arfenic. 
I'or conufiGn uie a pound of common fait may be fub- 
M. 
ftituted for the borax. This glafs cannot be recotn.r 
mended, as being very foft, and will not bear much wear 
if employed for rings, or fuch imitations of ftones as are 
expofed to much rubbing; but for ear-rings, ornaments 
worn on the head, or breaft, &c. it may laft a confide, 
rable tiijie.—To give pafte the different colours, the 
procefs is as follows : 
Amethyst. —Take ten pounds of either of the com. 
pofitions deferibed under Colouring of Glass, (in this vo¬ 
lume,) one ounce and a half of manganefe, ,and one 
dram of zafter ; powder and fufe them together.—For 
Black. Take ten pounds of either of the above coni- 
pofiitions, one ounce of zafter, fix drams of manganefe, 
and five drams of iron, highly calcined ; and proceed as 
before.—For Blue. Take of the fame compofition ten 
pounds, of zafter fix drams, and of manganefe two 
drams ; and proceed as with the foregoing. 
Chrysolite. —Take of either of the compofitions 
for pafte above-deferibed, prepared witliout faltpetre, 
ten pounds, and of calcined iron five drams ; - and pur¬ 
ine the fame procefs as with the reft. 
Red Cornelian. —Take of the compofitions men¬ 
tioned under ^■'‘Gl a ss, two pounds ; of glafs of 
antimony one pound ; of fcarlet oker ttvo ounces ; and 
of manganefe one dram. I'ufe the glafs of antimony 
and manganefe with the compofition ; then powder 
them, and mix them with the other, by grinding them 
together, and fufe them with a gentle heat. 
White Cornelian. —Take of the compofition juft 
referred to tw'o pounds ; and of yellow oker well walhed 
two drams ; and of calcined bones one ounce. Mix 
them, and fufe them with a gentle heat. 
Dia.mond.— Take of the white fand fix pounds; of 
red lead four pounds ; of pearl-alh purified three pounds; 
of nitre two pounds; of arfenic five ounces.; and of 
manganefe one Icruple. Powder and fufe them. 
Eagle-marine. —Take ten pounds of the compoli¬ 
tion under Glass ; three ounces of eppper highly cal¬ 
cined with fulpluir; and-one fcruple of zafter. Pro¬ 
ceed as before. 
Emerald.— Take of the fame compofition w'ith the 
laft nine pounds; three ounces of copper precipitated 
horn aquafortis ; and two drams of precipitated iron.. 
—Or, Take of natural cryftal four ounces ; of red-lead 
tour ounces ; verdegris forty-eight grains ; crocus mar— 
tis, prepared with vinegar, eight grains: let the whole 
be finely pulverized and fifted ; put this into a crucible,, 
leaving one inch empty ; lute it well, and put it into a 
po'.tiftr’s furnace, and let it ftand there as long as they 
do their pots. When cold, break the crucible ; and a 
matter will remain of a fine emerald colour, which, af¬ 
ter it is cut and fet in gold, will equal in beauty an ori¬ 
ental emerald. 
Garnet.— Take two pounds of the compofition un¬ 
der Glass ; two pounds of the glafs of antimony, and 
tw'o drams of manganefe.—For vinegar garnet, take of 
the compofition for pafte del'cribed above, two-pounds; 
one pound of glafs of antimony, and half an ounce of 
iron, highly calcined ; mix the iron with the uncoloured 
pafte, and fufe them; then add the glafs of antimony 
powdered, and c-entinue them in the heat till the whole 
is incorporated..—For Gold yellow, Take of the compoli¬ 
tion ten pounds, and one ounce and a half of iron 
ftrongly calcined ; proceeding as with the other.—For 
Deep purple, take of the compofition ten pounds ; of. 
manganele one ounce; and of zafter half an ounce. 
R'JBY.—Take one pound of either of the above 
compufit'ons for pafte, and two drams of calx Cajjii, or 
precipitation of gold by tin; 'powder the pafte, and 
grind the calx of gold with it in a glafs, flint, or agate^ 
mortar, and then fufe them together. A cheaper ruby 
may be made with half a pound of either of the above 
compofitions, half a pound of glafs of antimony, and 
one dram and a half of the calx of gold proceeding as 
before-. 
Satphlre^ 
