Dictionarium polygraphicum. The way to Enamel in all sorts of colours on gold and other metals.

Dictionarium Polygraphicum:
Or, The Whole Body of Arts Regularly Digested.
Vol I.
London: Printed for C. Hitch and C. Davis in Pater-noster Row, and S. Austen in St. Paul's Church Yard. MDCCXXXV.
The ancient works of Enamel on metals, were only of black and white, with some few tinges of carnation, or flesh-colour, as may be seen in the Limoge Enamel. In Francis the Itt's time it became more improv’d, and they made use of lights and shadows; but the Enamel on gold was of no better stuff than that on copper, and all the works of it on gold, silver, and copper, were of transparent matter; such as wrought it on thick, couched each colour by itself, as is done now a-days in enamelling some particular pieces of elief, and not otherwise.

Since they have found out the way of enamelling with opake and thick stuff, and the art of compounding the colours is much more improving and handsomer than that of the ancients, as is visible in all our modern works; we must without all exception, own the fair works upon gold, representing portraitures and entire histories, so neatly, and to the life, and co veted as much as picture done in oil, over which it has the advantage of natural lustre and varnish, which is never tarnished, to be the invention of this latter age, and the improvements therein we owe to the French.

All sorts of Enamel are not to be promiscuously employed on all sorts of metal. Gold which perfectly bears with, as well all the opake as transparent, cannot agree with clear purple, its yellow mightily changes the colour thereof, and produces but a very ill fancy. On the contrary, this purple is very fine on silver; so the egmarine, the azure, and green, all other colours, as well clear as opake, disagreeing therewith; and copper suits with every thick Enamel, but cannot endure the limpid, unless prepard for it beforehand, as shall be shewn in due place.

Observe, that good Enamel must be hard and lasting, such as is soft being full of lead, and subject to change colour, easily be coming sullied and foul. Of the clear Enamel, some is harder, some softer; the hardest is always the best, however, even of them there is choice; some lose colour in the fire, some are more or less lively and sparkling; but if you employ constantly such as we have before prescribed, you'll never meet with those inconveniences; for the ingredients being perfectly cleansed, will endure all degrees of fire, any change of colour or quality not ensuing.

Of the furnace for enameling and portraying.

The enameling of metals, as well as the colouring of the fluff, cannot be effected without fire, and is wholly different in this point from painting with the usual colours in oil, which may be dried in the air only, without other help.

It would be very hard to believe the fire would not spoil the mixture of the colours, if our daily experience which we made, did not vouch the contrary; however care must be taken not to let the work have too much time, but draw it out as soon as you find it polished.

The fire must be reverberatory, or rather of suppression, and never to be under the stuff; ’tis the same as is used for cleansing of metals, whether in mints or goldsmiths shops, which is very familiar to all the world.

You must have the furnace round or square, either of iron or earth, it's no great matter, how (or whether of these) it is, which must be hollow in the middle, to contain the work with a good charcoal fire all about, and over it, to make it melt the better; and you must have it so as to be able to take your stuff out, and put it in again, as occasion requires. You may, for better conveniency, make use of a goldsmith's muffle; ’tis a small arch, made of crucible earth, in the shape of half a crucible, cut lengthwise, and they place it on the area or floor of the furnace, the opening of it lying just against the mouth of the furnace, to put in and draw out the work easily; and for more conveniency, they place a small grate over it, which must not touch it, for fear of breaking it; and on this gate make a good fire, and so round about the muffle, to heat the hollow very well, under which they put the work to be enamel'd and painted; and the essays or tria's they have a mind to make on a little iron-shovel, to draw the easier out; but for making essays of ingredients for Examiel, it must be a little blade of white Enamel, which ought to be provided purposely for that use.

The way to Enamel gold.

We have already said, that golf, silver, and red copper may be enamel'd; now to make true work, you must use only pure gold, because silver makes white Enamel appear yellow, and copper rises in scales, and makes vapours; for though all Enamel sticks to it, yet it is but very imperfectly, and may be easily divided and peel'd off again; besides, the colours are so wretched on it, that they lose much of their charm and lustre by the impurity of that metal.

Therefore, if you would have good work, let gold only be your subject, and of the purest, if you employ clear Enamel, because on impure gold they grow dull, and become imperfect, that is to say, there appears with this a certain obscure and cloudy vapour in the Enamel, which deadens and takes way the life of its colour.

The gold plate ought to be rising, and when it is forged very even, the goldsmiths apply white Enamel over and under it, tho’ it is to be wrought but on one side; but this is necessary for two reasons; first, because the work is neater and fairer for it; and again, because if it were only enamel'd on one side, the fire would swell it, and so make it rise, and that in bubbles; because it is always as it were tormented, especially when the pieces are great, and the Enamel carelesly laid on; this makes it produce blisterings, which disfigure the work. The French chymists call such vegeter, but their goldsmiths petits ouillets. This disfiguring of the work, you may avoid, by laying Enamel on both sides of the plate of gold, and thicker over than under. This will keep it equal and even on both sides, the first lay of white Enamel remaining smooth in this condition, serves for a field to place all your other colours on as we will farther discourse of in the art of portraying.

Oil of spike is used for dissolving thick and opake Enamel before it can be applied; for the transparent you need use nothing but fair water, as we shall shew anon; and then 'tis couched flat and border'd with the metal, and sometimes we don't border at all, the field being Enamel; but this is troublesome, because the limpid Enamels as they melt, often mix, and so confound the colours, which constantly happens when the pieces are small.

Red Enamels are not so, unless by chance, and come generally yellowish out of the fire; as soon as 'tis applied to the gold, it alters the colour; one may soon bring it to a perfect red Enamel, by turning it at the mouth of your furnace, when you are taking it out from the fire; and then it is that the workmen say they make it red, and give it its compleat colour.

Gold, as we have already said, admits of all sorts of Enamel, clear or opake, bright purple excepted, which is altered by the yellow-colour of the gold, and does not take so good effect there, as on silver, on which it ought still to be used. The way of working every sort of Enamel is alike.

To Enamel on silver.

We have already taken notice that silver agrees not with all sorts of Enamel, as gold. We repeat it here again to prevent the use of any but such as serve to produce perfect and agreeable effects.

You are to make least use of white Enamel on silver, because there it becomes yellowish, and unpleasing; but nothing can suit better with it, than bright purple, green, blue, and egmarine, because the whiteness of the silver is then clearly eminent, and gives its just splendor.

The work and manner of enamelling on silver, is no way different from that of gold, in forging the plates evenly to prepare them for the Enamel; you may make use of white on the under side, since the Enamel there serves only to qualify the risings and disturbings of the metal in the furnace, which would cause unevenness, or disagreements in the surface, and prevent its becoming just and handsome.

We need not repeat again that way of placing the Enamel on your plates of gold or silver, and so to put them into your little reverberatory furnace (spoken of before) to melt, and as soon as polished to be taken from the fire.

To Enamel on copper.

Though we have before touched upon the way of enameling on copper, yet lest the reader should too slightly apprehend it, we shall therefore treat of it here to avoid imperfection.

The less use is made of this metal in this work the better, for the Enamel never sticks to it perfectly, but is easily scaled, divided, and broken off, which never happens to gold; besides, the copper is so impure, that its fumes destroy the beauty of the Enamel so much in the furnace, that they quite lose their charm and splendor by the malignity of those vapours.

Though the copper receives easily all thick or dark Enamels, it can't be brought so well to endure the clear and limpid; now if you would make use of these last, you must first lay a lay of green, or black, and thereon a leaf of silver to receive the Enamel suitable for that metal mentioned before; so that in the main 'tis much better to make use of silver for the transparent Enamels, since the copper is so apt to foul, and the change in either the same.

In enameling on copper, you must take a plate of red copper forged smooth and even, applying your Enamel of what colour you desire above and under the plate as before; then put this into the reverberatory furnace, and when it receives its polishing, draw It Out.

To prepare the Enamel for the metals.

Before you apply your Enamel on the metal, you must give it this little preparation, which is the easiest, and best approved of by the goldsmith. We will instance it in white Enamel, because that is more generally made use of than any other.

Take white Enamel, pulverize it very fine, pour on it a little aqua fortis, and let it afterwards purify and refine in a small glass cucurbit.

Wash it afterwards often in fair water, dry and keep it in a close vessel for use.

To make use of it, first pound a quantity thereof in a stone mortar, wetting it with a little water, and so spread it on the plates, and into the furnace with it as before.

Thus do with all your clear and transparent Enamels, and you'll have all your things in a readiness to go on with your work as you think convenient.

To prepare the colours for painting on Enamel.

Nothing can be more splendid than the paint on Enamel, and for this use must be chosen the liveliest and most noble colours, and such as will easily vitrify and melt.

All these before assigned, are as equally sufficient for this, as for enamelling; if you grind them first on your marble with the best oil of spike, or mix them together with the other ingredients for that purpose, as we shall give a fuller account hereafter, and of all the matters to be used with calcined Enamels, which serve to make up the paint for Enamel, mixing them well together, as painters do on their pallets. When you want some colours of Enamel, you may with blue and yellow make a good fair green; a blue and red mixt, will produce a fine vio let; a red and white creates a rose-colour; a black and whit forms a gallant grey, and so of others.

Every workman has his own secret, and peculiar way of working; but most of them make use of rocaille for varnishing their colours, which has an ill effect, because of too much lead, which is not perfectly purged off. This lessens the lise and splendor, and it always continues as it were tarnished, cloudy and dull.

But our Enamel being well refined, will produce work so fine and agreeable, that 'tis not possible to find anything so illustrious and accomplish'd; and such as for their own private diversion would work herein, and have not the conveniency of a glass-house, may be easily furnished, by proceeding to make one ac cording to directions given. See the plate in the article furnace.

Notwithstanding the sufficiency of our Enamel for affording all sorts of colours and tinges in painting on Enamel, we will yet prescribe other means for this, no way inferior thereto, to answer the advantage and curiosity of those who work at this excellent art.

To make white for painting on Enamel.

The best workmen, for the most part, use the white Enamel ground, which: they can manage with address enough to heighten and illustrate their lights, which is necessary to be done to all their colours, as in miniature. But as it is difficult to pre serve the ground justly for improving those other colours, and ordering the compositions (all one as in carnation) you must take of our crystal ground, prepared with tin and lead purg’d and re fin’d as before-mentioned, or rather of our milk-colour Enamel, which is the fairest can be made; cleanse it with aqua fortis; wash, dry, and grind it afterwards with oil of spike.

Or you may prepare another white ground without lead, thus: take very pure tin calcin'd, and let it vitrisy in a glass-house pot, with eight times as much crystal fritt, as we have directed the preparation before-mentioned. Pulverize these very fine, and proceed precisely, according to prescription for purification, &c.

To make a black for painting on Enamel.
Though the black Enamels prescribed before, and those succeeding it, may serve to paint on Enamel with this colour, with out any other preparation than grinding it with oil of spike: yet we will add here another black no less excellent and fine, arising from equal parts of black Enamel, and peregrine well calcin'd; mix, and reduce them to an impalpable powder, and then apply. oil of spike, and you'll have a colour which will take with great facility on the Enamels.

A yellow for paint on Enamel.
We will only make use of our Enamel, prepar'd as before, mixt and purified with aqua fortis, and after wash'd in clean water, as before-mentioned; dry and grind this powder with oil of spike on your marble, and 'tis fit for use. With this yellow and blue, as we have already hinted, may be made a fair green; but those Enamels described before are so just and fine, that 'tis needless to use any other for that purpose. This prepa ration for the yellow here laid down is sufficient also for it, with out any farther trouble.

A blue to paint on Enamel.
The Enamels of this colour affign'd before, are the noblest can be used in this work; purify them with aqua fortis, and grind them with oil of spike, as before directed for the other colours.
You may, because it is vitrified, make another blue fine e nough, thus. Take painters Enamel prepar'd; add to this (put into a glass-bottle) best rectified aqua vitæ, enough to drown the fluff by four inches; stop it well, and set it in the sun-shine five or six days, shaking the bottle well three or four times a day, that the purer Enamel may dissolve, and the grosser fall to the bottom. Take the Enamel out of your bottle, and steep the faces, letting them precipitate as useless; then evaporate your aqua vita, and dry your azure, which will be a very fine well cleansed matter for all sorts of this work; grind it after on your marble. This Enamel so prepar'd, is most proper for painting, and far beyond the ultramarine, so much used.

A red paint for Enamel.

There can nothing exceed the perfection of our Enamels of this colour, taught in eight several articles before-mentioned; the like may be said of our blood-colour, rubies, rose, and carbuncle, which is the most exalted ingredient for enameling metal, or making paint on Enamel; and those who practise this fine art, use no other than that of the glass-house, or such as they make accordingly. Now this red Enamel is prepar’d as the other co fours with aqua fortis to purify it, wash'd, dry'd, and ground with oil of spike for your use.

There is yet another tolerable red, which they paint with on Enamel, in which is employ'd calcin'd gold; but this would be much more improv’d, if instead of their racaille, they made use of our matter made of crystal and saturnus glorificatus, or of our principal prepar’d powder before prescrib'd, for these are ex ceedingly well purified, whereas the rocaille has too great a surcharge of lead, the impurity whereof always renders the work defeative.

One takes an ounce of fine gold in very thin plates, these dissolv’d in eight ounces of aqua fortis, and regulated with sal armoniac, or old strong salt, in a small glass matrass; this is put into a glass-cucurbit, wherein was already pour’d eight Paris pints of spring water, and six ounces of Mercury; the cucurbit is plac'd on a still fire, and after twenty-four hours, the gold descends to the bottom in a light land-red powder; then the water is pour'd off leisurely into an earthen glazed receiver, or pan, and the powder gather'd and dry’d by a moderate heat, and with a shamois skin they separate the mercury from the gold, and grind this powder with twice its weight of flowers of sulphur together; and then put all into a crucible over a small fire, where the sulphur will communicate it self with the rest, and then evaporating, they find the powder somewhat ruddy, which ground with rocaille, is what they make use of on the Enamel.

We own this calcination to be tolerable as to the gold; but as for mixing the calx with the rocaille, without melting them together to incorporate, is disputable. We believe that in grinding them together with oil of spike, they may in some sort incorpo rate as other colours, but can never so perfectly unite; besides, the crystal matter does not so well receive the colour of the gold this way, as if it were done by fusion.

Others make red inclining to vermilion, which they use in painting after this manner. Take vitriol calcin'd in two crucibles well luted together, and set for an hour over a slow fire; then purge it with aqua fortis, wash it in fair water, and grind it with oil of spike as before, and so make use of it for Enamel.

All red Enamel which is good, ought to be hard, and not easily consumed in the fire; for that which is otherwise, contains much lead, and soon becomes dull and sullied, and is not of so lasting a substance, which the workmen ought to be cautious of.

To finish the preparation of Enamel, and before the manner of painting them is prescrib'd, observe, that all the colours before mentioned, which are not pure Enamel, ought to be incorporated with a crystalline matter, such as we have prescrib'd, to the end they may vitrify the better, which else they'll not easily do, though most workmen make use of their rocaille, whether to avoid the trouble of making (or that they are ignorant how to prepare) a better matter; and this has obliged us to give several ways very good and true for this purpose to make fine and perfect work by.

The way to paint on Enamel.

This art is revered by all nations, ’tis so fine and so excellent, that the first and noblest persons in the world practise it, as we have said elsewhere. It is certain that the art of painting on Enamel is modern, but no less estimable for that, since its effects are so wonderfully beautiful, so infinitely lasting, of so natural a gloss, and their splendor never to be defaced.

If it were possible to make large works of Enamel, as is done in picture, they would be inestimable because of their lustre, and so far surpass what antiquity has had such great respect for, and which these latter ages still caress with extraordinary esteem.

This way of painting on Enamel seems much more difficult than limning; practice however convinces us, that they are equally easy, and we can with as little trouble represent history on Enamel, as in limning; the difference lies only in preparing the colours, which is not done the same way; for we dry and varnish our Enamel paint by fire, whereas that in limning is done by the air.

To paint on Enamel, you must have a plate of gold enamel'd with white, on which delineate and portray your design. This done, draw it over again in dark red; the piece being perfectly done off, and the lines complete to the subject, set the tablet, or piece in the muffle, on a reverberatory fire, to settle as before directed.

Your tablet being taken out, apply the colours in a just order as in limning, with this difference only, that here you make your white ground serve for filling, where that colour is required to set off the heightnings and lustre of the lights, as is done in miniature; and because it mightily contributes to the heightening thereof in the other colours as to improving their lights, according to the directions before-mention'd.

When the piece is thus finish'd, put it again into the furnace to fix the colours, and as soon as you perceive it varnish or polish, draw it out, left the colours mix and spoil each other.

You may take out the work again, and revise it as often as you please, only putting it still into the furnace, until it receives its just gloss, &c.

This way of renewing and revising the tables, is done in limning with oil; and the painters observe, that the pieces must not be handled until they are well dry’d in the air, so those in;must be let alone until they receive their perfection from the fire.

This is all to be observ'd in painting on Enamel; it remains only for us to shew how to prepare your dark red for tracing the design; you may have it thus.

Take the caput mortuum which remains in the retort, after the aqua fortis is made of your vitriol and nitre, grind it with oil of spike, and so you have the dark red ready for your use; or you may make it with crocus Martis, ground with oil of spike.

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