Part III

PART III.
The art of enamelling in ordinary and the method of preparing the colours.
THe art of of painting in enamel - curious instructions how to make artificial pearls.- of doublets and foils, and the manner of colouring thme.-the art of counterfeiting precious stones, with other rare secrets

Of Enamelling in Ordinary; and of preparing the Enamel-Colours,
ENAMELLING is the art of laying a coat of enamel upon metals, as gold, silver, copper, &c. and of burning-in various colours by the fire, so as to preserve indissoluble the figures and letters which are formed of them. Several receipts are in the possession of curious ar¬tists, many of whom excel in this useful art; of these we shall now proceed to give the detail.

To prepare the Flux for Enamel-colours,
Take four ounces of red lead, and one ounce of well washed and clean sea sand ; melt them together, and put them in a cold ingot. ’
Another Sort of Flux, which is very soft.
Take one ounce of white lead, a quarter of an ounce of red lead, twelve grains of pebble; heat the pebbles red hot, and quench them in urine; repeat this until you can crumble them to an impalpable powder between your fingers; then beat them fine; put them with the ingredi¬ents into a clean crucible; lute it well, and when dry, give it a fierce fire for half an hour, or longer ; then take it off the fire, and let it cool of itself; break the crucible, and melt the contents again in another clean crucible, and pour it into a clean ingot, or. a bright brass weight- scale, and then it will be fit for use ; beat and grind it in an agat mortar*, to an impalpable powder. When you mix your colours therewith, temper as much as you have occasion for with oil of spike, i. e. spike-lavender.

A Green Colour.
A green colour is best made by mixing blue ayfyettew together, and by adding a little brown, if it be required to be dark. The reason is, that greens are otherwise made from copper, which must retain some portion of the acid in which it was dissolved if it remain green; and if you dissipate all the acid it becomes dusky, which will happen cm exposing the enamel to fire.
Take copper, and dissolve it in aquafortis; then evapo* rate. Take of this one part, and three parts of flux. Or9
* A mortar of Wedgwood’s ware is as good, and much easier ob¬tained. Ed.
Take a copper plate, and with a piece of pumice-stone with water, rub it over; receive the water into a bason or dish, and let it settle; pouroff* the water, and neal the settling; then take thereof one part and three parts of
flux; and this makes a good and fine green.

Dark Green.
Take green enamel two parts, yellow smalt one- eighth part, and six parts of verditer.
Yellow Colour.
Take fine King’s yellow, and neal it in a crucible $ one part yellow, and three parts flux.
-4 high Yellow.
Take gold-yellow enamel, vitriol and flux; grind and temper them to your mind with oil of spike.
Brimstone Colour.
Take calcined JVizpZ^-yellow one part, three parts of burned lead-yellow, and three parts of flux.
A Black Colour.
Take three-fourths of black enamel, and one-eighth of scales of iron; grind these with water, in an agate mortar, very fine; draw the water from it, and dry it upon hot plates; then grind it with oil of spike. Or9
Take manganese; neal it upon a tile; the blacker it comes off the fire the better; take one part thereof with three parts of flux, ground with oil of spike.

A good Red.
Take green vitriol; grind it fine, and dry it in the sun; then neal it between two crucibles, well luted, so as to prevent the air’s coming to it. Take thereof one part* and two parts and a half of flux; melt them together, and when you use them, grind them with oil of spike.
Another. ' *
Take Roman, or blue, vitriol, about the quantity of a walnut; grind it in a stone inortar, very fine ; dry it, and then neal it to a brown colour ; take the lumps, and put them into a new glazed pipkin, and pour aqua fortis upon themthen wash the aquafortis from them again, and let it evaporate; take afterwards one part thereof, and three parts of flux ; grind it with oil of spike.
Another good Red.
Take brown red, colcothar of vitriol, or Paris red, and a little flux ; grind them fine with oil of spike. Or,
. Take vitriol, calcine it in a clean crucible, and when dry, pour a little aquafortis and vinegar on it; neal it well; after that wash it with clean water, till it has no taste; dry it over a fire ; and when dry, neal it again; then take of this one part, and three parts of flux.
Blue Colours.
Take fine smalt; wash it well with clean water, as fine as possible; put a little flux to it, and grind it with oil of spike. Or,
Smalt may be used alone without the flux-powder, ground with oil of spike. Or,
Take ultramarine one part, flux four parts; grind them
with oil of spike.
Green.
Take verditer, and a little ground flux $ grind them with oil of spike. ,
Grass Green. '
Take verditer, andnealitin a crucible; take one part of it, and fhree parts and a half of flux.
Brown Cqlours.
Take crocus martis one part, flux two parts; grind them with oil of spike.
Purple Colow.
Take one part crocus martis, one part smalt, and three parts flux. Or, '
Take blood-stone, and grind it with vinegar ', when it is fine, wash it clean, and burn it oyer a candle on a thin plate.
Hair Colour.
Take umber, and neal it in a crucible ; then take one part thereof, and three parts of flux; grind them with ojl of spike.
Fawn Colour.
Take vitriol, glow it as hot as possibly you can, i.e, give it a red heat; then take of it one part, and three parts flux.
Carnation

Carnation Colour.
Take yellow ochre, and glow it in a crucible very hot; after that let it cool, and beat it in an iron mortar, and, if it is not of a fine colour, neal it again; take of this one part, and three parts and a half of flux.
A steel Red for Enamel.
Take fine thin beaten plates of steel, and cut them into small shreds; put them into a vial with aquafortis, and when reduced over a slow fire, neal it; of this take one part, and three parts of flux.
The ancients that laboured in this noble art, were un-acquainted with the beauties the moderns have discovered, particularly in the art of compounding colours for repre¬senting portraitures and history : the fine performances in those particulars are the admiration of every curious be¬holder. Besides their peculiar beauty and lustre, they have this advantage over all other paintings, that they are not subject to the injury of the air or weather, as paintings in oil or water colours; and unless they are rubbed or scratched with any thing harder than themselves, the co¬lours will retain their beauty for ever, and be as fine and bright as when first done.
This art cannot be effected without fire, which always must be reverberatory, in a furnace so contrived that the fire may play all over the muffle that covers your work. To explain this more fully, see plate 4. When your re¬' verberatory
verberatory is building, Jet the month part of the muffle be placed fronting the mouth of the furnace, and be fixed in such a manner that the furnace file may not play into it, nor the ashes drop upon your work.
Your furnace may be either round or square; it may be of iron or earth, no matter which; only let there be SD much room in the inside as will contain the muffle, with a good charcoal fire round about to cover it: you must have a slice, or iron plate, to put your work upon, which, with a pair of tongs, convey into the furnace, and bring out again.
The metals fittest to enamel upon, as has been said, are gold, silver, and copper; but the best work is performed on gold, for silver makes the white enamel appear of a yel* Jowish hue ; and copper is apt to scale, whereby the enamel is subject to break jn pieces; besides, the colours lose a a great deal of their charms and lustre to what they do Upon gold. The gold used for this purpose should be the finest, dse the impurities of a bad allay will have the same effect in the enamel colours as the silver or copper,
Your plate, of whatever metal it be, must be very thin, raised convex j both that and the concave side are laid over with white enamel; the convex side, whereon you paint, must be laid a small matter thicker than the other. You must observe, that the white enamel which you lay on the convex be ground with fair water in an agate mortar, and with an agate pestle, until it be fit for use : the enamel for the other side must be tempered with water whereiq yo# have before steeped some quince kernels.
As to the enamel colours which you paint with, you must take great care that they be equally tempered, or your work wil be spoiled ; if one be softer than the other, when your work comes into the furnace and grows hot, the soft colour will intermix with the hard, so as to deface your work intircly: this may serve to caution you to make trial upon a white enamelled plat$ for that purpose, of all your . enamels, before you begin your work: experience will di¬rect you further.
Take particular care that not the least dirt imaginable come to your colours, while you are either painting or grinding them; for the least speck, when it is worked up with it, and when the work comes to be put into the rever¬beratory to be red hot, will leave a hole, and deface your work.
After you have prepared your plate with a-white eftamcl, and it is ready to paint upon, apply your colours on an ivory palette, or a piece of glass, in just order, and first delineate your design with a dark red, made of crocus martis ground with oil of spike; put the piece in the muffle, and with a reverberatory fire, as before directed, fix that colour; and then proceed, remembering to dilute the thick and opaque enamel colours with oil of spike; and the transparent ones with fair water: by mixing blue and yel¬low enamel colour you have a fair green; blue and red a violet; red and white a rose colour; and so of other con¬tours.
We shall here set down several other receipts for pre¬paring enamel colours, which will not only serve for ordh- nary work, but for enamel-painting in miniature,
To prepare the principal Matter for Enamel Colours.
TAKE lead fifteen pounds, platc-tin ashes sixteen pounds; mix and calcine these, as directed in the first part; after you have calcined your lead and tin, search out the calx, and put it into an earthen pot filled with water; set it over a fire, and let it boil a little ; after which, take it off, and pour the water into another vessel, which will carry the more subtil calx along with it repeat this till you can subtiliae no more of the calx, and the water comes off clean without any mixture. What gross part remains in the pot, calcine as before, and this repeat till you can draw off no more of the subtil matter. Then pour the water from all your receivers into one that is larger, and evapo¬rate it on a slow fire. *.
Of this calx take 12 pounds, frit of white sand, beaten and sifted, 12 pounds, nitre purified 12 pounds, salt of tar¬tar purified * two ounces. Put these powders all together into a pot, place it in a glass-house furnace for ten or twelve hours to digest and purify. Then take and reduce it to an impalpable powder, and keep it in a close, dry place for use. Thus is your first or principal matter for enamel colours prepared.
To make Enamel of a Milk-white Colour.
TAKE three pounds of the fore-mentioned principal matter, twenty-four grains of prepared magnesia, and ar¬senic two pounds; put these together into a melting-pot, to melt and purify over a fierce fire; when the matter is melted, throw it out of the pot into fair water; and having
* You may buy salt of tartar purified, or you may purify it yourself. Calcine tartar of red wine in an earthen crucible, till it comes black ; continue the fire till it changes to a white. Then put it into an earthen pan, glazed; fill the pan with clear water, and boil it over a gentle fire, so that in four hours the wa¬ter may evaporate the fourth part; then take it otF the fire, and after the water is settled and cold, pour it off by inclination into a clean glazed pan, and you will have a strong lye. Then pour clean water on, and let them boil as before: this repeat, till the ' water becomes infipid ; then filter the lye ; put it in glass vefiels upon 3, sand-bath, in a gentle heat, to evaporate, and at the bottom there will remain a very white salt. Dissolve this salt again in fair water, and let it stand two days Xo settle ; filter it, and evaporate at a gentle fire, as before, and you will have a salt whiter than the former repeat this three or four times, and your salt will be whiter than snow itself.
The same process may be employed on pot-ash, without cal¬cining it as the tartar is; the same may be done also on pearl- ash.
afterwards dried it, melt it again as before ; do this for the third time, changing the water; when you have thus puri¬fied it, and found the white colour answer your intent, it is done ; but in case it has still a greenish hue, add a little more magnesia, and, by melting it over again, it will become as white as milk, and be fit to enamel with on gold or other metals: take it off the fire ; make it into cakes, and pre¬serve it for use.
A Turcoise Blue Enamel. '
TAKE of the principal matter three pounds ; melt and purify it in a proper melting-pot, then cast it into water; when dry, put it again into a pot, and being melted over again, add to it at four times this composition: scales, thrice calcined*, two ounces and a half; prepared zaffre forty-three grains ; prepared magnesia twenty-four grains; stone-blue two ounces; mix and reduce these to a very fine powder; stir the matter very well with an iron rod, for the powders to incorporate. When your matter is thus tinged, observe well whether your colour answer your in¬tention before you empty the pot: if you perceive the tinging powders are too predominant, add more of the principal powder; and if too faint, add more of the ting¬ing powders. Your own judgment must direct you in the managehient of this preparation.
* To calcine copper scales, such as come from the hammer of braziers or copper-smiths: wash them from their foulness, put them into a crucible ; place it in the mouth of a reverbetatory furnace, for four days; after which, let them cool; then pound, grind, and fift them. Put this powder a second time into the fur¬nace, to reverberate four days longer; proceed as before; and after it has stood again the third time for four days, reduce it into powder, and it will be fit for the use intended. ‘

A fine Blue Enamel.
TAKE two pounds of the principal matter; one ounce of prepared zaffre, or of indigo blue; twenty-two grains of copper, thrice calcined; mix and reduce these to a fine powder, and put them into a melting-pot: when the metal is melted, cast it into water; then dry it and put it into the pot again ; let it stand upon the fire until it is well in¬corporated; take it off; make it into cakes, and keep it for use.
A Green Enamel.
TAKE two pounds of the principal matter, one ounce of copper scales, thrice calcined, twenty-four grains of scales of iron, blue vitriol two ounces, yellow arsenic one, ounce; mix and reduce these to an impalpable powder, and, at three several times, or in three several portions, fling it into the principal matter, stirring the metal so as to tinge it equally. When the colour is to your liking, let it stand for a while in the fire, to incorporate thoroughly; then take it off, and you will have a delicate green. Or,
Take * Feretto of Spain two ounces, forty-eight grains of crocus martis, yellow arsenic two ounces; pulverize and mix these well, and put them into a white glazed potf ;
* Feretto of Spain, is thus prepared : stratify thin plates of cop-' per with vitriol, in a crucible; put it in the mouth of a glass fur¬nace for three days; then take it out, and add to the copper fresh layers of vitriol, stratifying them as before : now put the crucible in the same place of the furnace; repeat it six times successively, and you will have an excellent feretto. Beat this to powder, and it will tinge glass of an extraordinary beautiful colour.
f The best melting-pots for glasses and fluxes are made of to¬bacco-pipe clay. They may be had of Mefirs. Pugh and Speck, melting-pot manufadory, bottom of Booth-Street, Spital Fields. Ed.
set it in the furnace to melt, and refine the matter; after which cast it into water ; and when dried, throw it again into the pot: when melted, observe whether the colour is to your liking; if so, let it stand for some time longer to refine. If you find the colour too faint, add more of the tinging powder.
A Black Enamel.
Take of the principal matter two pounds, prepared zaffre one ounce, and prepared manganese one ounce ; pulverize and mix these, and proceed as directed in the preceding colours. Or,
Take of the principal matter three pounds, zaffre one ounce, crocus martis one ounce, feretto of Spain one ounce; pound and mix them, and proceed as directed before.
A Velvet-black Enamel.
OF the principal matter two pounds, red tartar two ounces, prepared manganese one ounce; pulverize these, and put them into a glazed pot, bigger than or¬dinary, because the matter will rise; for the rest, proceed as directed before.
A Purple-colour Enamel.
OF the principal matter two pounds, prepared manga¬nese one ounce, indigo blue half an ounce; proceed as above. Or,
Principal matter three pounds, prepared manganese one ounce and an half, of twice calcined scales of cop¬per three ounces, stone blue one ounce; pulverize and proceed as directed.
A Violet
A Violet Enamel.
OF the principal matter three pounds, prepared manga¬nese one ounce, thrice calcined copper scales twenty-four grains, terra verte one ounce ; pulverize and mix these all together, and proceed as before directed.
• A Yellow Enamel.
OF the principal matter three pounds, tartar one ounce and a half, prepared manganese six grains, yellow orpi- ment two ounces, arsenic one ounce; pulverize them, and proceed as before directed.
An excellent Red Enamel, of a very splendid-ruby Colour.
THIS enamel is of a surprising beauty, and its lustre equals that of a red ruby. To prepare this, take equal quantities of manganese and nitre; let them reverberate and calcine in a crucible in a furnace for twenty-four hours; take it then off, and wash it well in warm wa¬ter, to separate the nitre; dry it well, and the mass will be of a red colour: to this add an equal quantity of sal-ammoniac; grind this on a marble with distilled vi¬negar, as painters do their colours; dry it, and pulve¬rize it; then put it into a strong matrass, and let it sub¬limate for twelve hours; break off the neck of your matrass, and mix all the volatile and fixed parts together, adding the same quantity of sal-ammoniac as there are flowers, and take care to weigh them before the compo¬sition ; grind, pulverize and sublimate as before, repeating this until your manganese remains fuzible at the bottom of the matrass: this preserve to tinge your crystal with ; and according to your liking, add either a greater*or less ' quantity of the manganese, or of the crystal, until you have brought it to its degree of perfection

A Rose Colour EnameL
TAKE five pounds of ground crystal*; melt it in a cru¬cible ; add, at four different times, two ounces and a half of thrice calcined copper; stir the metal every time ; then pour into it crocus martis and manganese prepared as directed; let it stand for six hours to cleanse, and if the colour is too light, add a little more crocus martis, until it be of a fine rose colour.
Observe that all the colours, (which are not pure enamel,) must be incorporated with the crystal, that they may vitrify the better, which else they would not easily do. Some workmen make use of rocaille ; but that does not answer the purpose so well a$ ground crystal
A fine Purple.
Take half an ounce of fine gold ; neat it, and beat it into very thin plates; dissolve this in four • ounces of aqua regia; put it into a glass cucurbit, and set it on warm ashes, or sand, to dissolve; put m it a small matter of nitre ; when all is dissolved, drop two or three . drops of oil of tartar into it, and stop the cucurbit close, to prevent its boiling over : then put in some more drops of oil, and repeat this until it hisses no more. Af¬ter this put some lukewarm rain-water to it, and let it stand for some time, and a powder will settle at the bot¬tom of the cucurbit; then pour off the water leisurely into an earthen, or glazed receiver; put more fresh water to the sediment, and repeat this until the water cornea off
clear, and free from the sharpness of the aqua regia. When the powder is settled, and all the water poured from it, then put it upon a piece of whited-brown paper, to separate it from the rest of the water; and dry it on a warm tile; or in the sun. To one part of this powder, add six parts of the principal matter; grind it with oil of spike, and it will make a good purple. .
A,good Red Enamel Colour.
Take green vitriol; put it into a copper cup; hold it - over a fire, and stir it with a copper wire until it is reduced to a powder; burn tins upon a hot tile, on which let it cool of itself; then wash it with rain water, and when settled, pour off that, and put fresh water on, and thus repeat it «several times*. >
But some artists, instead of washing this powder,
. boil it in fair water, and think this method better than that of washing. With this powder you may tinge the principal matter to what height you would have your co¬
lour. Or,
Melt vitriol in a crucible, with a cover, and burn over a gentle fire; when thus you have burned it to a powder, boil it in clean watér; filter and dry it: of this take one part, of the principal powder three parts, and of trans¬parent yellow one and one-eighth part. Or,
Put vitriol into a crucible, pour a little aqua-fortis upon . it, and neal it gently; then put it in a clean earthen pip* kin, pour clean water upon it, and boil it one hour; then pour off that, and put fresh water upon it; wash it, and when settled dry it; neal it once more, and it is fit for use.
* This, and some others are, in reality, the same thing with Col- cothar of vitriol; so are the following, with a little variation, viz. scarlet ochre, Spanish brown, Indian red, Venetian red. Ed.
Of this powder take two parts, and of the principal pow¬der, or flux, three parts.
A Flux for Red Enamel.
Take of red lead four ounces, white scouring sand one ounce ; melt it, and pour it into an iron mortar.
Some General Observations.
Before we proceed to another subject, we will con¬clude this article with a few observations and general rules, for the more easy apprehending of what has been said already.
Observe that gold is the most proper metal to enamel upon ; that every colour, except a violet or parple, re¬ceives an additional beauty from it, to what it does from silver or copper: that it is best to enrich gold with such beautiful colours, since they raise admiration in the beholder when the skilful artist places them in due* order.
The ancients only painted in black and white, with something of a carnation, or flesh colour; in process of time they indeed made some few improvements, but all their enamel colours were equally alike on gold, silver, or copper, every one transparent; and every co¬lour wrought by itself. But since the modern artists have found out a way of enamelling with opaque co¬lours, and of compounding them in such a manner as to shade or heighten the painting in the same manner as is done in miniature, or oil painting, this art has gained the pre-eminence in small portraits, having the advantage of a natural and lasting lustre, which is never tarnished, nor subject.to decay.
The purple coloured enamel does best on silver, from. Which it receives great beauty; so does the ultramarine, azure and green; all other colours, as well clear as opaque, do not suit it; copper suits with all thick enamels, but is unfit for that which is clear.
Make choice of good, hard, and lasting enamel: the soft is commonly full of lead, which is apt to change the colours and make them look sullied and foul; but if you follow the prescriptions, you will meet with no such inconvenience.
Remember, when you lay white enamel on gold, silver, or copper, to dilute it with water of quince-ker¬nels, as has been directed: clean enamel colours, mix ónly with fair water; and the opaque, when mixed with fluxj or the principal matter, dilute with oil of spike.
Be careful not to keep your work too long in the furnace, but take it often out, to see when it has the pro¬per glazing; and then it is finished.
Before you use your enamels, grind as much as you have occasion for, with fair water, in an agate mortar; thus do with all your clear and transparent enamels, and by this means you will have all things in readiness to proceed in your work with pleasure.
All opaque colours that will stand the fire, are fit to be used in painting enamel. The ingenious artist will not be at a loss, but will meet probably with several colours not yet discovered, as frequently happens to those who try experiments.


Vol II
The laboratory of artificial pearls
It will not be improper to treat in this place of artificial pearls, as it is a branch of jewellery.
The ancients who wrote on the several Sorts of precious stones, ranged pearls among the jewels of thfe first class; they have at all times been in high esteem, and have been employed particularly in adorning the fair sex.
The oriental pearls are the finest, on account of their size, colour, and beauty, being of a silver white ; whereas, the occidental or western pearls seldom exceed the colour of milk. The best pearls are brought from the Persian Gulf, above the isles of Ormus and Bassora*. They are found in Europe, both in salt and fresh waters; Scotland, Silesia, Bohemia, and Frisia f, produce very fine ones; though those of the latter country are very small.
Art, which is always busy to mimic nature, has not been idle to bring counterfeit pearls to the greatest perfec¬tion : they are imitated so near, that the naked eye cannot distinguish them from pearls of the first class, or the real ones.
We shallherc present the curious with several receipts how to counterfeit pearls in the best manner, and after a method both easy and satisfactory, so as to render his labour pleasant, and -make it answer his expectations. ,
To imitate fine Oriental Tearls.
TAKE of distilled vinegar two pounds, Venice turpen¬tine one pound; mix them together into a mass, and put . them into a cucurbit fit a head and receiver to it, and, after you have luted the joints, set it, when dry, on a
* Called also Bal sura and Basrah. Ed.
+ That part of Germany lying between the Rhine and the Ems.
. Ed.
. sand furnace, to distil the vinegar from it; do not give it too much heat, lest the stuff should swell up.
After this, put the vinegar into another glass cucurbit, in which there is a quantity of seed pearl, wrapt in a piece of thin silk, but so as not to touch the vinegar; put a cover or head upon the cucurbit; lute it well, and put k in Bal. Maria *, where you may let it remain a fortnight.
The heat of the Balneum will raise the fumes of the vine¬gar, and they will soften the pearls in the silk, and bring them to the consistence of a paste; which being- done, take them put, and mould them to what bigness, shape, and form you please. Your mould should be of fine sil¬ver, the inside gilt; you must refrain from touching the ƒ paste with your fingers, but use silver gilt utensiis, with which fill your moulds; when you have moulded them, bore them through with a hog’s bristle, or gold wire, and let them dry a little; then thread them again on a gold ' wire, and put them in a glass; close it up, and set them in the sun to dry; after they are thoroughly dry, put them into a glass matrass in a stream of running water, and leave them there twenty days; by that time they will con¬tract the natural hardness and solidity of pearls. Then . take them put of the matrass, and hang them in mercury • water t, where they will moisten, swell, and assume their ‘ oriental
* Balneum M arise, sometimes called Balneum Maris, is a bath of sand, heated by a fire, in which chemical apparatus are plung¬ed, to submit their contents to a digestive heat. Ed.
f Mercury-water, so called by the workmen, is thus prepared. Take plate-tin of Cornwall; calcine it, and let the calx be pure and fine; then with one ounce of the calx, and two ounces of pure mercury, make an amalgam ; wash it with fair water, till the water remains insipid and clear ; then dry the amalgam thoroughly ; put it into a matrass, on a sand bath, giving it such a heat as is requi¬site for sublimation. When the matter is well sublimated, take off the matrass, and let it cool.' Take out that sublimate; add one ounce of Venice sublimate to it, and grind it together on a marble ;
K 2 put oriertal beauty; after which shift them into a matrass, hermetically closed up, to prevent any water coming to them, and let it down into a well, to continue there about eight days; then draw the matrass up, and on opening it yoli will find pearls exactly resembling oriental ones. This method is very excellent, and well worth the trouble.
Another Way to make Artificial Pearls.
TAKE oriental seed-pearls; reduce them into a'fine powder, on a marble ; then dissolve them in mercury-wa¬ter, or clarified juice of lemons. To make more dis¬patch, set them in a cucurbit, in bal. mar. and you will see presently a cream arise at the top, which take off im¬mediately: take the solution off the fire, and, when set¬tled, pour off the liquid into another glass, and save it. You will have the pearl paste at the bottom, with which fill your silver-gilt moulds ; then put them by for twenty- four hodrs: bore them through with a bristle ; close up the moulds, in barley dough, and put it in an oven to bake, and when about half baked, draw it out, take out your ‘pearls, and steep them in the liquor you saved before, putting them in and taking them out several times: then close them up in their moulds, and bake them again with , the like dough; but let it remain in the oven till it is al¬most burnt, before you draw it out. After you have taken your pearls out of their moulds, string them on one or
put this into another matrass; close it well, and set it upside down in a pail of water ; and the whole mass will dissolve in a little time.: this done, filter it intb a glass receiver; Set it on a gentle sand heat to coagulate, and it will turn into a crystalline substance: this beat in a glass mortar, with a glass pestle, to a fine powder; sift it through a fine sieve, and put it into a matrass; stop it close up, and place it in bain, maria; there let it remain till it resolves again .into water; which is the mercury -w at er, fit for the above-mentioned use. ,
more .gold or silver threads, and steep them in met&nry* water for about a fortnight; after which time, take and dry them in the sun, in a well-closed gUss, and you wijl have very fine and bright pearls.
Another Jfray.
DISSOLVE very fine pulverised oriental pearls in alum* water; when the solution is settled, pour off the water, and wash the paste first in distilled water, then in bean water, and afterwards set it in bal. mar ice or horse-dung, to digest for a fortnight; this done, take out your glass, and the matter being come to the consistence of a paste, moyld it as you have been directed before ; bore and string the pearls on a silver thread, and hang them in a welk closed glass alembic, to prevent the air coming to them; thus dried, wrap every one up in leaves of silver; then split a barbel, and close them up in the belly thereof; make a dough of barley meal, and bake the fish, as you do bread; then draw him, take out your pearls, and dry them in a closed glass in the sun.
To give them a,transparency and splendor, dip them in paercury-water; or, instead, take the herb gratuli*, and squeeze it in water ; put therein six ounces of seed-pearl, one ounce of nitre, one ounce of roach alum, one ounce of litharge ; the whole being dissolved, heat first the pearls, and then dip them in this solution to cool; repeat this about six times successively.
If your pearls should not have/ their natural hardness, then take two ounces of lapis calaminaris, in impalpable powder; add to this two ounces of acid of vitriol, and two ounces of whites of eggs beaten into a water; pu$ them together into a retort; lute a receiver to it, and you
* Probably gratiala^ i. e. hedge-hyuofa is here meant by the UR* known term gratuit. Ed.
Will distil 1 fair Water, with which, aüd soiüé fine barley flour, make a paste, in which put your pearls, and bake them as before; thus they will become exceedingly hard.
Another Method.
TAKE chalk well purified and cleansed from all gross¬ness and sand, i. e. whiten; of this make a paste, and form pearls, in a mould for that purpose; pierce them through with a bristle, and let them dry in the sun or in an oven; then string them on a silver thread; colour them lightly over with Armenian bole, diluted in the white - of egg$; and when <ky> drench them with a pencil and fair water; lay them over with leaf silver, and put them under a glass in the sun to dry; when dry, polish them with
a dog’s tooth.
To give them the true colour, make a glue of vellum shavings, thus: after you have washed them in warm water,, boil them in fair water, in a new earthen pot or pipkin, to some thickness, and then strain them through a cloth. When you would use it, warm it first, and dip your string of pearls into it, but let there be an interval between each pearl, so as not to touch one another; this will give your pearls a natural lustre.
To form large Pearls out of small ones, as directed by
Korndorffer.
Take of mercurial water fourteen ounces ; put two ounces of sulph, solis *, into a low matrass, pour the mer* curial water upon it, and let it dissolve and extract. Then take of the whitest small pearls twenty ounces, put them into a proper matrass, and pour the said water upon it.
' *
* Sulphur Solis may probably mean a preparation of silver, not now in use. Ed.
The pearls will’ by degrees dissolve, and at last turn to a clear calx, much like dissolved silver calx: pour off the mercurial water ; boil the calx well out, and dry it; then put it into a clean crucible by itself, and melt and cast it* into what form you please. When cold, polish it in the same manner as you do gems or crystals; and you will have your work of the consistence and beauty of the finest and clearest oriental peart
To make of small Pearls a fine Necklace of large ones.
TAKE small oriental pearls, as many as you will; put them into mercurial water fifteen days and nights together* and they willturn soft, fike a paste; then have a pearl mould, madevof silver; into this convey the paste by a silver spatula, or such like implement; but you must not touch the paste with your fingers, and be very careful to have every thing nice and clean about this work: when it is in the mould, let it dry; bore a hole with a silver wire through it, and let it stick there till you have more, but take care they do not touch one another; then have a glass wherein you may fix, as upon a pair of stands, your wires with the pearls: put them, well closed up, in the sun to harden, and when you find them hard enough, put them into a matrass; lute the neck very close, and sink it in a running spring of water fox twenty days, in which time they wilt contract their natural colour-
It is asserted, by those who have wearied themselves with the hopes of forming small imperfect pearls into larger ones, that artificial pearls cannot be made of the materials of original pearls. The foregoing receipts are laborious and expensive; and that the reader may have some reward for his exertions, should the experiments balk his expectations, we shall add to this edition a tried and approved method of imitating pearls from other materials,
which, when well executed, can only be distinguished from the real by their absolutely containing fewer ble¬mishes. The method was kept a profound secret for many years.
Best Method, of imitating Pearls.
Take the blay ór bleak-fish, which is very common in the rivers near London, and scrape off, in a delicate way, the fine silvery scales from the belly. Wash and rub these in fair water, changing the water, and permitting the seve¬ral liquors to settle : the water being carefully poured off, the pearly matter will be found at the bottom, of an oily consistence, called by the French essence d'orient. A little of this essènce is dropped into a little hollow glass bead of a bluish tinge, and shaken about, so as to fill up all the cavities and surface of the interna] part. When the essence is thoroughly dry, melted white wax is drop- . ped into the' beads, to give them weight, solidity, and security. ' t
To clean Pearls when of a foul Colour.
TAKE pigeon’s dung; moisten it with alum-water, to the consistence of a paste: put this into a glass, big enough to hold four times the quantity; put into this your yellow- coloured or foul pearls, so that they may be covered all over, and set them in a warm place, or behind an oven $ let them stand for a' month ; then take them out, and fling them into fresh cold alum-water, and dry them care¬fully, and your pearls will become fine and white: if you repeat the operation once or twice, they will be done tQ greater perfection.

To blanch and cleanse Pearls.
FIRST soak and cleanse them in bran-water; then in milk-warm water, and last of all, steep them in mercury- water : then string and hang them in a glass; close it well, and set them in the sun to dry.
The bran water is made thus; boil two large handfuls of wheaten bran in a quart of water, till all the strength of the bran is drawn out: use it thus; take a new glazed earthen pah, in which put your pearls on a string, and pour the third part of the bran water upon it; when they have soaked, and the water is just warm, rub your pearls gently with your hands, to clean them the better; conti¬nue this until the water is cold; then throw off that, and pour on another third part of the bran water that is boil¬ing ; proceed with this as you did before, and when cold throw it away, and pour on the remainder of the water, still proceeding as before; after this, heat fair* water, and pour it on your pearls, to refresh .them, and to wash away the remairts of the bran, by shifting them, and pouring on fresh warm water: this do thrice, without handling your pearls; then lay them on a sheet of clean white paper; and dry them in the 6hade $ then dip them into mercury water, to bring them to perfection/
Other Methods used in blanching Pearls.
POUND plaster of Paris to an impalable powder; rub the pearls therewith very gently; this will not pnly cleanse them, but if you let them remain in this powder twenty- four hours afterwards, they will still be the hotter for it. White coral has the same effect, used in the like manner.
White tartar calcined and divested of all its moisture, is Very good for the same purpose. ,
Salt, well dried and ground, is as effectual as any of the
former things, for cleansing of pearls, by rubbing them therewith; and if afterwards you lay them up in some ground millet, it wiltrontribute to their natural brightness.

Of doublets.
A doublet, among lapidaries, implies a counterfeit stone composed of two pieces of crystal, with proper co-* lours' between them; so that they may make the same appearance to the eye as if the whole substance of the crystal had been tinged with these colours.
• The impracticability of imparting tinges to the body of genuine natural crystals, without depriving them of their brilliancy, gave inducements to the introduction of colour¬ing the surface of them, so as to give them, when finished,
’ the appearance of a gem. They have not the property which artificial stones have of being set transparent, as is required for, drops of earings, &c. but they suit very well for rings, and other ornaments which allow of an opaqüfe back-ground. They are made after the following manner:
A crystal, or glass in imitation of crystal, is to be cut by a lapidary into the shape of the precious stone it is to resemble $ a brilliant, for instance, must be composed of two separate stones, or two parts of one stone, forming the upper and under parts of the brilliant, dividing the whole stone in a horizontal plane, a little lower than the middle. No division appearing between the two pieces when duly polished and placed on one another, the colour of the intended stone is put between them, after the fol¬lowing method:
Take of Venice or Gyprus turpentine two scruples, and add to it one scruple of the grains of mastich, chosen per-fectly pure, free from foulness, and previously powdered; Melt them together in a small silver or brass spoon ladle,
* and put to them some one of the colouring substances mentioned hereafter, they being also finely powdered: stir them, together as the colour is put in, that they may be thoroughly commixed. Warm then the doublets to the same degree of heat as the melted mixture, and paint the upper surface of the lower part, putting the upper one instantly upon it; and press them to each other, taking care that they are conjoined in the most perfectly even mannet. When the paint or cement is quite cold and set, scrape off the redundant part of it which has been pressed out of the joint, so as to leave no colour on the outside of the doublet. They should be so set as skilfully to carry the mointing just above the joint, which will hide the arti¬fice and secure the pieces from separating.
As the proportions vary in the receipt given in the former editions of this work, we shall here insert it, lest it be thought, on trial, to have the preference: it is as follows— *
Method of making Doublets.
TAKE two drachms of clear mastich, and of the clearest Venetian or Cyprian turpentine sixteen drams; dissolve these together in a silver or brass spoon: if* you find there is too much turpentine, then add a little more mastich to . it, to bring it to a right temper. Then take what colour you please, as lake, dragon’s blood, distilled verdigrise, or what colour else you design, for representing a particular stone; grind each by itself, in the nicest manner you pos¬sibly can, and mix each apart with the mixture of mastich and turpentine, which you ought to have ready by you 5 and you will find the lake to imitate the colour of a ruby, the dragon’s blood that of a hyacinth, and the verdigrise the colour of an emerald. But in case you would have yoyr colours, as it were, distilled, then get a little box,
made
made of lime-tree, in the shape of an egg or acorn. This box must be turned at the bottom as thin as possible, so that the light may be seen through it. Then make a quan¬tity of any one of the abovesaid colours, mixed with the mixture of mastich and turpentine, and put it. into the little box, hung over a gentle glowing coal fire, or in sum¬mer-time in the heat of the sun, where the colour will distil through very fine ; scrape and put this into little boxes of ivory, to preserve it from dust, for your use ; it is ne¬cessary to have to every different colour such a different wooden box.
When the colours are ready, take your crystals (first ground exactly to fit upon one another) and make your colours and stone of an equal warmth; lay your colour with a fine hair pencil on the sides of the crystals that are to be joined together; then clap them against each other as nimbly as possible : press them with your fingers close together; let them cool, and it is done.
The colour of the Ruby is thought by some ingenious artists to be best imitated by a fourth part of carmine, with some of the finest crimson lake that can be procured.
The Sapphire may be counterfeited by very high Prus¬sian blue, mixed with a little of the above-mentioned crimson lake, to give it a tinge of the purple hue. Let not the Prussian blue be too deep coloured, or you must use the less of it, otherwise it will give a black shade which will obscure the brilliancy of the doublet.
The Emerald may be well imitated by distilled verdi,- grise, with a small portion of powdered aloes. But the mixture should not be strongly heated, nor kept over the fire after the verdigrise is added, for the colour is impaired by it.
The resemblance of the Garnet may be made by dra¬gon’s blood ; which, if it cannot be procured of sufficient brightness, may be helped by a small quantity of carmine.
The Amethyst is imitated by the mixture of some Prussian blue with crimson lake; but the proportions can only be regulated by experience, as the parcels of blue and lake vary so much in their hues, and are of such different strengths of colours.
The Yellow Topaz may be counterfeited by mixing powdered aloes with a little dragon’s blood, or by good Spanish anotto ; but the colour must be sparingly used, or the colour will exceed that of the stone.
The Chrysolite, Hyacinth, Vinegar Garnet, Eagle Marine, and other such weak and diluted colours, may be formed and imitated in like manner, only with less propor¬tions of the due colours; for which purpose, those who employ their ingenuity and leisure hours in this pursuit, should obtain an original stone of each of those specified,^ keeping his eye perpetually watchful whilst mixing the colours. When these precautions are taken, and the ope¬ration is well conducted, it is practicable to bring the doublets to so near a resemblance of the true stones, as to deceive the best judges (when they are well set, and the joint hid) unless inspected in one direction only. The direction alluded to is, to hold them betwixt the light and the eye, so that the light may pass through the upper part and corners of the stone ; when it will be readily perceiv¬ed whether there be any colour in the crystal; which can¬not be learned by looking down upon the doublet.
The Crystal Glue of Milan.
This is nothing else but grains of mastich, squeezed out of a linen bag by degrees over a charcoal fire, and like clear turpentine. Its use is, to unite two pieces of crystal together, to form a doublet, precisely in the manner be¬fore described. '

Instructions
H9 the laboratory.
Instructions concerning foils, or metallic leaves, which are laid under precious stones.
IT is customary to place thin foils, or leaves of metal under precious stones, to make them look transparent, and to give them an agreeable colour, either deep or pale: thus, if you want a stone to be of a pale colour, put a foil of that colour under it; again, if you would have it deep, lay a dark one under it: besides, as the transparency of gems discovers the bottom of the ring they are set in, artificers have found out these means to give the stone an additional beauty.
These foils are made either of copper, or gold, or gold and silver together: we shall first mention those made of copper only, which are generally known by the name of Nuremburg or German foils.
Procure the thinnest copper plates you can, the thinner they are the less trouble they will give you in reducing , them to a finer substance: beat these plates gently upon a well polished anvil, with a polished hammer, as thin, as possible; but before you go about this work, take two iron plates, about six inches long, and as wide, but no thicker than writing-paper; bend them so as to fit one on the other; between these neal the copper you design to hammer for the foils, to prevent ashes, or other impurities getting to it ; then, taking them out, shake the ashes from them, and hammer the copper until cool. Then take your foils to the anvil, and beat them until they become very thin, and whilst you beat one number, put in another between the irons to neal; this you may repeat eight times, until they are as thin as the work requires. You must have a pipkin with water at hand, in which put tartar and salt, of each an equal quantity; boil, and put the foils in, and stir them con¬tinually, until, by boiling, they become white: then take them from the fire; wash them in clean water;
[143] dry them with a clean fine rag, and. give them, another hammering on the the anvil, until they are fit for your purpose.
N. B. Care must be taken in the management of this work, not to give the foils too much heat, to prevent their melting; neither must they be too long boiled, for fear of aftractingtoo much salt.
How to polish and colour Foils. r
Take a plate of the best copper, one foot long, and about five or six inches wide, polished to the greatest .perfection: bend this to a convex* shape, lengthwise, and fix it to a bench, or table: then take some whiten,, and having laid some on the roll, and wetted the cop¬per all over, lay your foils upon it, and with a polish- stone and the whiten, polish your foils, until they are .as bright as a looking-glass then dry them between a fine rag, and lay them up secure from dust. I shall now shew how these foils are coloured; but shall first give a short description of the oven, or furnace, requisite for that purpose. '
The furnace must be but small and round (see plate 4, -and the explanation) about a foot high, and as wide ; ,cover the same with a round iron plate, in which is a round hole, about four inches wide ; upon this furnace put another without a bottom, of the same dimension as the former, and let the crevices of the sides round about be well closed and luted: this furnace must also have a hole at'top. The lower furnace must have a little door at bottom, about five inches big. Before this'fix a sort of Tunnel, like a smoke-funnel to an oven, and lute it close to the furnace; then light some charcoal on your hearth, and when they burn clear, and free from,smoke, convey Them through the funnel into the furnace, till they come up so high as to fill half the funnel. When every thing is ' ready,
ready, and you have a clear fire, then begin to colour your foils in the following manner :
Lay the foils upon a pair of iron tongs; hold them over the hole that is at top of the furnace, so that the fumes of the coals may reverberate over them, and move them about till they are of a brownish violet colour; and this is done without any other vapour or smoke. When you have done with this colour, put it by; and if you would colour others of a sky blue, then put the foils upon the tongs as before ; and whilst you, with one hand, are hold¬ing the foils over the holes, fling, with the other, some down-feathers of a goose, upon the live coals in the fun¬nel, and with a red-hot poker press them down, to drive the, smoke of the feathers up through the holes of the oven, which, by settling upon the foils, gives them a fine sky colour: but you must have your eyes very quick upon them, and, as soon as you see that they have attracted the colour you design, take them away from the oven, to pre¬vent their changing to some other colour: if you would have your foils of a sapphire blue, then first silver them over; which is done in this manner:
Take a little silver and dissolve it in aqua-fortis; when dissolved, put spring water to it; fling thin bits of copper into it, and-the water will look troubled, and the silver precipitate and hang to the copper; pour off that, sweeten the silver with fair water, and let it dry in the sun ; when dry, grind it on a porphyry: then take one ounce of tar¬tar, and as much of common salt; mix and grind them all together, till they are well mixed ; fling this powder upon the thin foils, and rub them with your finger backwards and forwards, and it will silver them ; then lay them upon the polisher, pour water over them, and some of the powder, and rub it with your thumb till they are as white as you would have them: polish them with a polisher of blood-stone; and then holding them over the goose-fea¬ther smoke, they will take a fine dark blue.
To colour Foils of a Green Colour, for an Emerald.
You must fitst colour your foils of a sky blue, as di¬rected before ; then hold them over the smoke-hole, and below, in the funnel, lay, upon the red-hot iron plate, leaves of box, from which ascends a smoke that gives the foils a green colout; but before they contract that colour they undergo several changes, as blue, red, and yellow* &c. wherefore you must hold them till you have the green colour to your mind.
To colour the Foils of a Ruby Colour.
Put the shearings of scarlet cloth upon the coals, and holding the foils over the smoke-hole, they will cöntract A fine red colour.
The Colour of an Amethyst.
This may be obtained by proceeding with your foils as for the blue or sapphire Colour; for, before that blue colour comes, it first changes to an amethyst; as soon as you perceive this, take them off, and polish them.
How Foils are to be mixed with Copper and other Metals.
These are more difficult to make, but more lasting in their colour. Take one pound and a half of copper, and melt it in a crucible; fling into this two ounces and eleven penny-weights of gold ; when in fusion, pour it into a flat Ingot, and let it cool: this beat and work, as has been taught, into thin foils; then boil them in tartar and salt. These sort of foils will take a fine ruby colour; nor can that colour be well done without this mixture.
VOL. i. L Another
Another Way. '
Take small-coah dust; put it into a little iron oveny* and in the midst thereof a live charcoal; blow it till all the small-coal dust is lighted, and let this glow for two hours:
- when it is nearly all glown out, add such another quantity to it, and let it glow for an hour. - At the top of your oven must be a round or square hole, with a close cover to itr in which hang the foils to some copper or iron wire: when your small-coal has glowed for about an hour, take a little iron bowl, and warm it well;: put in it a little quantity of fox hair, and then set it upon the small-coal dust; shut the oven door, and open the top : this will draw the smoke through, and give the foils, first, the colour of a ruby, then of an amethyst, and, lastly, a sapphire. You may take out such colours as will serve your purpose; and if you want a.green, let those foils hang, and burn sage leaves till the foils turn to a green colour. Take care to put but
a few sage leaves in at a time.
To the ruby and hyacinth-colours use pure copper; but for an emerald and sapphire, take one part of gold, two parts of silver, and eight parts of copper;. melt, and work, them together-
The art of imitating precious stones, or of making artificial gems
This curious art is arrived at such perfection, as to b$ capable of imitating precious stones in their lustre, oolour, and beauty, equal to the natural ones,' except in hardness, to obtain which has been, and no doubt still is, the endea¬vour of ingenious men.
[147]
The art of making artificial gems, consists chiefly in, rightly imitating the tints of those that are real: these must be prepared from such things as resist the fire, and do not change their colour.
You must therefore take such colours as change not, when mixt together: therefore, since blue and yellow make a green, you must take such blue as shall not hurt the yellow when you mix them 5 and also such a yellow as shall not be detrimental to the blue ; and so of the other colours. We shall give plain instructions to carry the in¬genious artist with ease through his experiments.

The Way of preparing Natural Crystal.
Take natural crystal, the clearest you can get, no mat* ter how big the pieces are ; fill a large crucible with them, and cover it with a lid broader than the mouth of the cru¬cible, to prevent the falling of ashes or coals into it: then put it into a small furnace, on burning coke: and when the crystal is thorough hot, cast it into a pretty large vessel of cold water. Then take it out of the water, dry it on an earthen plate, and put it into the same crucible again, cover it, and proceed as before, repeating it twelve times running, and changing each time the water: when the crys¬tal easily breaks and crumbles, and is thoroughly white, it < is a sign that it is calcined enough: if there appear any black parts in the veins, break off the white, and put these again into the furnace, and proceed therewith as before,
till only the white remain behind.
After you have dried this calcined crystal thoroughly, grind it to an impalpable powder, on a marble or porphyry, and sift it through a lawn sieve. Of this powder of crys¬tal, as it is used for all artificial gems of which we shall treat, it will be proper to have a sufficient quantity by you, to have recourse to when afrwork; and if you would sue* ceed in this art, you must not use ordinary frit of crystal, L 2 ' be
[148]
be it ever so good; for that will not answet, or come up * to the lustre or beauty of natural crystal.
To counterfeit an Opal.
AT Harlem they make counterfeit opal glass, which is very lively, and whose several colours are supposed to be produced by different degrees of heat. When the com¬position is thoroughly melted, some of it, taken out on the point of an iron rod, being cooled, either in the air or water, is colourless and pellucid, but being put again into the mouth of the furnace upon the same rod, and turned round for a little time, acquires such various positions, as that the light falling on them being variously modified, re¬presents the several colours observable in the true opal. And it is remarkable that these colours may be destroyed, and restored again by different degrees of heat.
To make a fair Emerald.
Take of natural crystal four ounces, of red-lead fouÈ ounces, verdigrise forty-eight grains, crocus martis, pre¬pared with vinegar, eight grains; let the whole be finely pulverized and sifted: put this together in a crucible, leav¬ing one inch empty; lute it well, and put it into a potter’s furnace, where they bake their earthen ware, and let ft stand there as long as they do their pots. When cold, break the crucible, and you will find a matter of a fine emerald colour, which,* after it is cut and set in gold, will equal in beauty an oriental emerald. If you find that your matter is not refined or purified enough, put it again, the second time, in the same furnace, and in lifting off the cover you will see the matter shining; you may then break the crucible, but not before; for if you should put the matter into another crucible, the paste would be cloudy and full of blisters. If you cannot comê to a potter’s furnace,
Artificial gems. [149]
furnace, you may build one yourself at a small expence*, in which you may put twenty crucibles at once, each with a different colour, and one baking will produce a great variety of artificial gems. Heat your furnace with hard and dry wood, and keep your matter in fusion twenty-four hours, which time it will require to be thoroughly puri¬fied ; and if you let it stand four or six hours longer, it will not be the worse for it.
A deeper Emerald.
Take one ounce of natural crystal, six ounces and a half of red lead, seventy-five grains of verdigrise, ten grains of crocus martis, made with vinegar; proceed as direfted before. Or,
Take prepared crystal two ounces, red led seven ounces, verdigrise eighteen grains, crocus martis ten grains, and proceed as before directed.
To make a Paste for imitating an Oriental Topaz.
The colour of this stone is like water tinged with Saffron or rhubarb: to imitate it, take of prepared natural crystal one ounce, of red lead seven ounces, finely powdered and sifted; mix the whole well together, and put it into a cru¬cible, not quite full by an inch, lest the matter should run over, or stick to tfie cover of the crucible in rising; then proceed as directed above. Or,
Take prepared crystal two ounces, native cinnabar two ounces ; as ustum two ounces (all finely pulverized and sifted), four times as much calcined tin; put it all together intq a crucible well covered, and proceed as before.
* The reverberating furnace, which belongs tq^he common port-able furnaces, will do for one crucible at a time. Ed.
To make an Artificial Chrysolite.
This stone is of a green colour, and some have the cas’t of gold; to imitate it, take natural crystal prepared two ounces, red lead eight ounces, crocus martis twelve grains; mix the whole finely together, and proceed as before, only leaving it a little longer than ordinary in the furnace.
To counterfeit a Beryl, or Aqua Marina.
THIS stone is of a bluish sea-green: to imitate it, take two ounces of natural crystal prepared, five ounces of red lead, twenty-one grains of zaffre prepared (the whole finely pulverized); put them in a crucible, and cover and lute it; then proceed as directed above, and you will have a beautiful colour, ’
A Sapphire Colour.
A Sapphire is generally of a very clear sky-colour, and is highly esteemed for its beauty. There are some of a whitish colour, like diamonds ; others, of a full blue; and some, of a violet.
To make this paste, take of prepared rock crystal two ounces, red lead four ounces and a half, smalt twenty-six grains; pulverize and proceed as directed. This colour will come near to a violet.
Another, more beautiful, and nearer the Oriental.
Take two ounces of natural crystal prepared, six ounces of red lead, two scruples of prepared zaffre, and six grains of prepared manganese (all reduced to a fine powder); mix, and proceed as before,
Another, deeper coloured Sapphire,
Of prepared natural crystal take two ounces, red lead five ounces, prepared zaffire 42 grains, prepared manganesé -eight grains ; the whole reduced to an impalpable powder, and mixed together; proceed as you have been directed, and you will have a colour deeper than the former, tending to a violet
7 b make a Paste for an Oriental Garnet,
A garnet is much like a carbuncle ; both, if exposed to the sun, exhibit a colour like burning coals, between red and yellow; and this is the true colour of fire. To imitate this stone, fake two ounces of natural crystal pre¬pared, and six ounces of red lead, also 16 grains of pre¬pared manganese, and two grains of prepared zaffire, pul¬verize and mix the whole ; put it into a crucible, and pro¬ceed as directed.
Another, deeper Garnet.
OF natural crystal prepared take two ounces, Ted lead five ounces and a half, prepared manganese 15 grains; pul¬verize all, and proceed as before directed.
Another process for counterfeiting of precious stones.
Take of black flint stones what quantity you please; put them into a pail of hot water, and, being wet, put them into a hot furnace, (this will prevent their flying into small
small pieces ;) or else warm them thoroughly by degrees, before you put them into the furnace. When you see that they are thoroughly red hot, quench them in fair watèr, and they will look of a fine white colour; dry and pulve¬rize them very fine: this you may do in an iron mor¬tar, but, as the powder may contract some of the iron, it will be proper, after you have taken it out, to pour on it some muriatic acid, which will clear it of the iron, and disengage it from impurities: wash it in several clean hot waters, afterwards.
Powder, thus prepared, is fit to be used for making the finest glass, and for imitating thé clearest and most transparent gems, especially those that require the lustre of a diamond or ruby: as for a sapphire, emerald, topaz, chrysolite, amethyst, &c. your labour with the acid may be saved, if your mortar be bright apd free from rust. Such as have a jnortar pf porphyry, or such like stone, havé no occasion to use an iron one, but will save them¬selves a great deal of trouble.
If you cannot get black flint stones, you may content yourself with pebble; but flint is far preferable, and makes the glass of a harder substance than that made of pebble.
* An approved Composition.,
OF the above flint powder take three parts, refiped nitre two parts, borax and arsenic one part. Or,
Of the flint powder three parts, nitre two, and borax four parts. Or,'
Of the flint powder two parts, of refined pot-ash, or salt of tartar and borax, of each one part. Or,
Take of flint powder seven parts and a half, purified pot¬ash five parts. Or, .
Flint powder six parts and an half; nitre two and a half; borax one half; arsenic one half; and tartar, one part.
To melt these Compositions; and how to tinge and finish
your Work.
Take any one of the above specified compositions, and weigh what quantity you please, (one or two ounces); thêa mix it with the colour you design to have it of; for instance.
To make a Sapphire. .
Take, to one ounce of the composition, four grains of zaffre; mix well together, and melt in a crucible; if you find the colour to your liking, proceed to finish it. You may make a sapphire either deeper or paler, according to what quantity you take of each ingredient; and it is the same with respect to other colours. A new practitioner in this art may make experiments in small crucibles, in order to acquaint himself with the nature of it.
I have already given receipts of post colours for imi¬tating precious stones; but, nevertheless, I shall here lay down some experimental rules necessary to be observed.
Kqow then that crocus martis may be prepared different ways, and each will have a particular effect in colouring of crystals; one is prepared with vinegar, another with sul¬phur, a third with aqua-fortis, and a fourth by only a rever¬beratory fire.
To prepare Crocus Martis with Vinegar.
TAKE iron, or, which is better, steel filings; moisten and mix them up with good strong vinegar, in an earthen dish, or pan; after which, spread them, and let them dry in the sun ; when dry, beat them fine in a mortar; moisten this powder with fresh vinegar, and dry and beat it again,' as before; repeat this eight times running; afterwards, dry
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and sift it through a fine hair sieve, and it will be of. the colour of brick-dust; but when mixt with glass, of a fine crimson colour. Put this powder up carefully, to preserve it from dust.
To prepare Crocus Mart is with Sulphur.
Take iron, or steel filings, one part; sulphur three parts; mix them together, and put them'into a crucible; jtover and lute it well; then set it into a wind-furnace, and give it a strong fire, with charcoal, for four hours together ; then shake it out, and, when cold, pulverize and sift it through a fine sieve: this powder put- into a crucible; lute it, and place the same in the eye, or hole, of a glass furnace; let it stand there for fourteen days or more, and it will turn to a red powder, inclining to purple: tliis is a very useful ingredient for tinging of glass.
To prepare Crocus Martis with. Aqua-Fortis.
Moisten some iron, or steel filings, in a glazed earthen plate, or dish, with aqua-fortis; set it to dry in the sun, or air; when dry, grind it to a fine powder; moisten it again > with fresh aqua-fortis; dry it, and proceed as before, re¬peating it several times, till you see it of a high red colour ; then grind and sift it through a fine hair sieve, and lay it up
safe from dust.
To prepare Crocus Martis* by a reverberatory Fire.
Take clean iron, or steel filings, and put it into a large pot, or pan, about the quantity of an inch high ; cover it well, and put it into a reverberatory furnace, or any other place where it may be surrounded with a strong heat an<J. flame ; the iron will swell and rise in a fine red powder, so as to fill the pot, and even force up the lid ; take off this powderf
Artificial gems. 155
powder, and you will find a good quantity of iron, caked together at the bottom, which put again into the furnace» where it will swell and rise into a powder as before; this continue until you have a sufficient quantity. This is the most valuable crocus, and of great use in the art of co* louring or tinging of glass for counterfeiting of precious stones.
To make a fine Hyacinth.
TAKE of crocus martis, or of that iron powder pre* pared by reverberation, eight or ten grains to one ounce of the composition.
The Opal.
THIS is made of silver dissolved in aqua-fortis, preci¬pitated by common salt; add to it some load-stone, and mix it up with the above composition : it gives divers co¬lours, so as to represent a natural opal.
* Of Chrystal.
SUCH as will save themselves the trouble of preparing the composition for counterfeiting precious stones, may use fine crystal or Venice glass, beat in a clean mortar to a fine powder; of this take eight ounces, borax two ounces, re¬fined nitre one ounce ; which mixture you may melt and colour, with little trouble.
Bartholomew Korndorfer’s Secret to make a Diamond of a natural Crystal.
Take the best polished crystal, no matter whether large or small, so it is but clear and transparent; put it in a crucible, with three times as much of my fixed sulphur of gold, so that the crystal may be covered all over with
with it; then, after you have put a lid over it, and luted the crucible well, let it for three days and nights neal in a strong fire; then take it out and quench it in spring water, in which red hot steel is quenched forty-six times running, and you will have a diamond which resembles a natural one in every respeö, and is right and good.
Thus far Korndorffer, but as to his sulphur he has left us in the dark.
How to m$ke a Diamond out of a Sapphire, according to
PORTA’S Description.
WE used to make it, (the diamond) the surest way, In this manner : we filled an earthen pipkin, or crucible, with quick-lime, and laid the sapphire in the midst thereof, co¬vering it first with a tile, and then with coals all over, blow¬ing them gently until we had a clear fire ; for if, it is blown too much, it may occasion the breaking of the stone.
When we thought that the sapphire had changed its co¬lour, we let the fire go out of itself, and took it out to see whether it was turned white ; if so, then we laid it again in the crucible, in order to let it cool with the fire; but if it had not the right colour, then we augmented the heat again as before, and looked often to sec whether the force of the fire had taken away all the colour, which was done in about five or six hours; if then the blue colour was not quite gone, we began our operation afresh, until it was white , and clear. It is to be observed, that the heat of the fire, in the beginning of the operation, must increase by slow degrees, and also in the same manner decrease ; for if the stone comes either too suddenly into the heat, or from the heat into the cold, it is apt to turn dark, or fly to pieces.
In like manner all other precious stones lose their co¬lour, some sooner than others, according as they are ei¬ther harder pr softer. The amethyst is very light, and re¬' quires [151]
quires but a slow fire, for if it has too much heat, it be¬comes dark, or turns to a chalky appearance.
This is the art whereby inferior precious stones are changed into diamonds; they are afterwards cut in the middle, and a colour given them; and hence become a se¬cond sort of false diamonds, or doublets.
To make a fine Amethyst. '
TAKE calcined flint-stone, and sift it through cambric* whereof take three quarters of an ounce > of fixed nitre, one quarter of an ounce ; of borax three quarters of an ounce; manganese one quarter of an ounce: then add fixed * nitre and borax, well mixed, to it; put it in a crucible into a wind furnace; give it at first a gentle heat until it is red hot, and thus keep it for a quarter of an hour ; then give it a strong fire for two or three hours; at last pour it into a mould, and let it cool by degrees, to prevent its flying asunder.
To make a Ruby, or a fine Hyacinth.
TAKE acid of vitriol one ounce, and mix with the same weight of water; in this dissolve filings, or very thin beaten steel; set the glass on warm sand; filtrate the solution be¬fore it is cold; then set it in a cellar, and it will shoot into crystals, which pulverize ; put it under a muffle, and stir it until you see it of a crimson colour; then take it off the fire, put it in a phial, pour on it good distilled vinegar, and after it has stood four days in a gentle warmth, pour off that vinegar, and pour fresh to it, and let it stand four days more; this repeat until the vinegar is observed to make no extraction; then pour off the vinègar, and there will remain at the bottom of yourrphial a crimSon* coloured powder; sweeten this well with warm water* This is the tincture-powder for the ruby .or hyacinthf.
Then take black flints ; calcine them well, as has been already directed, in order to bring them to a white powder* and sift this through cambric ; take thereof, and of borax, of each half an ounce, and of the aforesaid tincture- powder eight or nine grains; and mix well together in a crucible, and give it, for half an hour, a gentle fire: aug¬ment it by degrees, until you see your mixture in the cru¬cible as clear as crystal* and of a crimson colour; then pour into a mould of what shape you would have it.
Another Artificial Ruby.
BRASILIAN topazes, of a smoky appearance, may be artificially made into rubies by giving them a gradual heat in a crucible filled with ashes, till it be red-hot.,
To make a Ruby Balass.
Take prepared powdered flint three ounces, fixed nitre* i. e. purified pot-ash, one quarter of an ounce > borax three grains; some of the above-mentioned tincture-powder $ bf copper and iron fifty-four grains ; of prepared manga¬nese five grains ; mix all together, and put it into a new crucible ; give it, at first, a gentle fire, , till it begins to melt; then give it a strong fire, for two hours, and let it cool of itself*
. To harden Bohemian Diamonds.
Take black lead two ounces, golden talc two ounces* powder it fine, and mix it well together; then take off this
. f This is no other than crocus martis. Ed.
mixture, put it into a new crucible,, about half full, and place the said diamonds upon that powder, so as not to touch one another; then put of the powder as much upon* them as will fill the crucible,; cover and lute it, and set it in a cupel with ashes, so as to have the ashes a hand’s breadth about the crucible ; then give it a slow fire, and augment the heat by degrees, in order to preserve the stones from breaking, until the cupel which holds your crucible begins to be red hot; continue it thus for forty-eight hours, then let it cool, and take the stones out of the crucible, and yon will find them look black ,, polish them with ashes of tin ; they will not only have contracted a tolerable hardness, but have also a fine lustre, much resembling natural diamonds.
Plain, Directions for polishing these Counterfeits, and also*
natural Gems.
IT is to be observed that all glass, or artificial stones, may be cut and polished’after one method, namely, by strewing: fine powdered emery upon a leaden plate with water, and,- holding the stone firm, grinding it in what form or shape you please.
If you fling ground- tripoli, mixed with water, upon a pewter plate, and add a little copper ashes amongst it, it will have the same effect.
Pulverized antimony strewed upon a smooth plate of lead, with tripoli and vinegar, polishes not only glass, crystal, garnets, agates, and amethysts, but all-other na¬tural stones, except the diamond. The diamond is only cut with the diamond powder itself. Any such diamonds as can be touched by emery, lead, copper, or other mo tals, are false ;. and . this is a good test for knowing a real diamonds
All other precious and hard stones may be ground, or cut, with metal and emery; but the polishing is dif¬ferent.
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The sapphire is, next to the diamond, the hardest; it may be polished best with antimony and vinegar, or lead, or with calcined flint-stone and water, upon copper.
The ruby is polished like the sapphire. ,
The emerald and turquoise are polished with potter’s clay and water, on pear-tree wood; or with tripoli, upon wood ; or with emery, upon pewter.
The beryl is polished with calcined mother-of-pearl, or calcined muscle-shells, upon a board covered with white leather.
A balass is polished with antimony upon coppêr.
The cornelian, onyx, agate, and jasper, upon tin; of with tripoli, or calcined flint, upon pear-tree wood; or with antimony upon lead.
The amethyst, topaz, turquoise, and other soft stones, are polished upon a board of lime-tree wood, upon a plate of tin, and upon a board with leather. First polish it, top and bottom, upon the wood ; the small diamond cuts are done upon the plate of tin, and receive the last polishing upon the board that is covered with leather, with the fol¬lowing powder:
A Powder for polishing soft Stones* ,
Take iron scales, and mix them with vinegar and salt, and let them stand thus infused for three or four days^ the longer the better; then grind the mixture very fine; dry it, and put it in an earthen pot well luted; give it al good fire, and it will be fit for use*.
* This is simply a crocus, and therefore ordinary crocus raartis is equally as good. Ed.
PART