contact with the atmosphere, and absorbing its oxygen and light, it undergoes a flow and imperceptible combuftion, not effentially different from the speedy and violent one which it would undergo in the common mode of burning. It firft paffes, by imbibing oxygen, into the state of a more or lefs dark refin; lofes gradually its effen. tial hydrogen, which makes a new combination, and afterwards the oxygen itself, which has attracted the carbon; and at length leaves behind a thin layer of actual carbon, which in the end becomes black in the course of time, and confiderably obfcures the oil painting. By a continuance of the before mentioned flow combuftion, the carbon itself as it were burns alfo; if it be ftrongly acted upon by the light, it attracts the oxygen of the atmosphere, and again brings forward the carbonic acid or fixed air, which gradually flies off. By this which I may call the fecond degree of combuftion, the painting becomes dufty and friable like crayon painting. "Hence it appears, that one can hope only for a tranfient or deceitful effect from the refreshing of oil-paintings with oil; becaufe the harmony of the tones, which the painter establishes as suited for the moment, does not proceed with equal steps, and cannot preferve itself in the like measure for the course of a few years; as each tint, as they fay, ought to increase, or to speak more properly to burn, in proportion to its antiquity. It thence follows, that mere washing may be prejudicial to an old painting; and that refreshing paintings, as it is called, by daubing over the furface, from time to time, with new drying oil, is highly prejudicial, and ill calculated for the intended purpofe; fince the oil, when it becomes dry, contracts in its whole furface, carries with it the paint under it, and occafions cracks in the painting. New oil of this kind gives occafion to mineral paints to be reftored; But covers the picture with a new coat of refin, and then of carbon, which arifes from. the gradual combustion, and always caufes more, blackness, and the decay of the painting, which one wishes to preserve. appearance which the valuable works of ZEUXIS Sig. FABRONI, after fome farther obfervations, to prove that metallic oxyds or calces could not have been employed as pigments on fuch mummies as ftill retain their colours fresh, adds; "Thofe who are acquainted with the accuracy and certainty of the method not long fince introduced into che mical operations, will be convinced, that in 24 gr. of the encauftic painting, which I ventured to detach from the above-mentioned Egyptian fragment, to fubject it to examination, the mixture of 100th part of a foreign fubftance would have been difcovered with the greatest certainty; that the refin of REQUENO muft undoubtedly have been perceptible to me; and that the alkali of BACHELIER and LORGNA could not have efcaped the counteracting medium. But in this Egyptian encauftic I found nothing but VERY PURE WAX, though I varied my analyfis in every known method. I must therefore conclude, that modern learned writers, in refpect to this Egyptian mode of painting, were as far from the truth, as the accounts of ancient authors appear to me precife and fatisfactory; and that the encauftum, with which formerly the fore part of fhips and the walls of houfes and temples were painted, was different from foap or refinous crayons." Sig. FABRONI then anfwers the question, "In what manner can wax be rendered fufficiently liquid for the ftrokes of the pencil?" by quoting the words of VITRUVIUS, above cited; (lib. vii. c. ix.) After which he adds; "It here appears, that the Romans, who copied the Grecian procefs, which the latter borrowed from the Egyptians, mixed the wax with an oil, to make it pliable under the brush; but no "WAX, on the other band, undergoes a change maftich, alkali, or honey, as has been ingeniously very different from that of drying oil. Inftead of imagined, and which fome have thought might becoming black by the contact of the atmosphere, be employed with fuccefs. The difficulty now it increases in whitenefs, and according to its na- will be confined to point out in what manner this tural quality, is not decompofed in the air, and oil was employed. It does not appear that they it does not ftrongly attract the oxygen of the used thofe fat oils called drying oils; because calces or metallic afhes, which are commonly used they could have employed thefe as we do, within painting. Moreover, the fo called earths, out the addition of wax, which would have been fuwhich are in themselves white, and are never vari- perflous. Fat oils, which do not dry, would not able, either by the prefence or absence of oxygen, have been proper, as they would have kept the cannot be employed in oil painting, because that wax continually in aftate of a foft pomade or falve. fluid makes them almoft tranfparent, and caufes Befides, my experiments would without doubt them to remain as it were without body, and not have shown me the existence of any oily matter. to produce the wished for effect. That beautiful "With regard to effential or volatile oils, a knowwhite, which may be obferved on the before men- ledge of them is not allowed to the ancients, as tioned Egyptian encauftic, is nothing else than a the invention of diftilling is not older than the 8th fimple earth, and according to our author's chemi- or 9th century, and therefore falls in with the pecal experiments, achalk, which is alfo unalterable." riod of GEBER or AVICENNA." Yet it is certain, That the ancients were once acquainted with that to ufe wax in their encauftic painting, they the use of oil painting, and neglected it on ac- muft hate combined it with an ethereal volatile count of the great fuperiority of the encauftic, oil, of which no traces fhould afterwards remain; our author thinks farther' evident, from the dif- because this was neceffary for the folidity of the ferent accounts which we have of the ancient works, and because no oil was found in the fragpainting." Thus PETRONIUS praises the freshment that was examined. "But NAPHTHA is Nann VOL. XVI. PART II. fuch fuch an oil, much lighter (fays our author) than oil of vitriol itfelf." It is exceedingly volatile and evaporates without leaving a trace of it be hind. On this account it is ufed, when fignatures and MSS. are to be copied; because the paper, which is moistened by it, and fo rendered tranfparent, quickly becomes white and opaque as before, by the complete evaporation of the naphtha. That the Affyrians, Chaldeans and Perfians, were well acquainted with the properties of naphtha is khown to every fcholar; and hence our author thinks it highly probable, that it was used by thofe nations to render wax fit for painting. It appears to me, (adds he) that the Greeks, as was the cafe with many other things, learned encauftic from the Egyptians, who probably derived it from the Affyrians or Chaldeans; and if fo, we have discovered the real mixture ufed for ancient encaustic painting." To put the matter, however, beyond a doubt, Sig. Fabbroni prepared for an eminent Saxon painter a folution of Venetian wax, in highly purified naphtha, defiring him to mix it up with the colours neceffary for painting. The artist complied, and both he and our author were astonished, as well as all their friends, at the high tone which the colours affumed, and the agreeable luftre which the painting afterwards acquired, when rubbed over with a foft cloth. A fimilar folution of wax was made for another artist, in which the spirit of turpentine was used instead of naphtha with equal fuccefs. Our author therefore concludes, we think with reason, that, if he has ⚫ not difcovered the real compofition enployed by the ancients in their encauftic paintings, he has at leaft approached much nearer to that discovery than any of his predeceffors, who have employed their learned labours in the fame field of inveftigation. Philof. Mag. § IV. Of ĚLYDORIC PAINTING. This new fpecies of painting is little known, and capable of great improvement. The name is derived from exov, oil, and usag, water; be. cause these two liquids are employed in the operation. Its principal advantages are, that the artift is able to give the greatest finishing poffible to fmall figures in oil; to add to the mellowness of oil painting the greateft beauty of water-colours in miniature, and to do it in fuch a manner that it appears like a large picture seen through a glafs which diminishes objects. The following is the manner of proceeding: A piece of very fine linen, or of white taffety, is fized with ftarch, in the most equal manner poffible, on pieces of glafs about two inches fquare, the angles of which are blunted, in order that the cloth may cover them neatly and without wrinkles. When these pieces of cloth are fufficiently dry, a layer compofed of white lead finely grinded, and on of pinks or of poppies, the whiteft that can be found, is applied to them with a knife. When this layer is dry enough to admit of scraping, more may be applied, if neceffary. As it is of the greatest importance for the prefervation of this kind of painting, that the different layers be purged of oil, in order that they may imbibe the colours applied to them, it is ne ceffary that their surface be very smooth, very dry, and very hard. The artift is next provided with a circle of copper nearly two inches in diameter, one 4th of an inch in height, extremely thin, and painted on the infide with black. This circle is employed to contain the water on the furface of the picture. The preference is given to water diftilled from rain or fnow; because ordinary water, from the falts which it contains, is pernicious to this kind of painting. The colours must be grinded between two oriental agates, most carefully preferved from duft, and mixed with oil of poppies, or any other fc. cative oil which has been extracted without fire, and pure as water. All the colours being grinded, they are placed in a small heap on a piece of glass, which is covered with diftilled water in a tin-box. When the materials are thus prepared, the fubject is flightly traced on one of the pieces of cloth above-mentioned, with a lead pencil. The tints are formed on the pallets from the heaps of colours under the water, and the pallet placed as ufual on the left arm, with the thumb through the aperture. The picture is held between the thumb and fore-finger, supported by the middle, and the neceffary pencils between the third and little fingers. The hand is fupported on the back of a chair, that there may be full liberty of bringing the work near, or keeping it at a diftance from the eye. The pencils are cleaned with the effence of rectified turpentine. After having made the rough draught with the colours ftill fresh, the circle of copper, which ought to furround the picture, is fitted exactly to the furface. The diftilled water is poured within this circle to the height of one 8th part of an inch; and the body is leaned forward till the fight fall perpendicularly on the object. The third finger on the right hand must rest on the internal right angle of the picture. The artift, with a fine and firm pencil, runs over the first draught, to give colours to the weak places, and to foften those which appear too ftrong. As foon as the oil fwims on the top, the water is poured off, and the picture is carefully covered with a watch-glafs, and dried in a box with a gentle heat. When it is fufficiently dry to be fcraped almoft to a level with the knife, the above operation is renewed till the artist is satisfied with his work. In this laft work, the artift feels all the advan tage of this new method for finishing. The wa ter poured on the picture difcovers all the faults of the pencil, gives facility in fearching into the bottom of the fhades, and the power of correcting the work, and of rendering it perfect. When the work is finished, it is put under a cryftal, where there is no admiffion of external air, and dried with a gentle heat. PART III. OF OECONOMICAL PAINTING. SECT. I. Of the UTENSILS and MATERIALS neceffary for OECONOMICAL PAINTING. THE object of this Part is to give an account of fome mechanical proceedings in certain kinds of painting, calculated to preferve and embellifh the walls of houfes and furniture. This branch of the art extends to every part of architecture. The whole building becomes the workshop of the artist; the stairs, the balluftrades, the fathes, the doors, and the railing of all kinds, occupying his first care, and then the cielings and wainscotting. The artist gives to all his fubjects a chofen and uniform tint; but he has it in his power to vary the colours on different parts of the building, in fuch a manner as to produce the most pleafing effect. Among the utenfils of the painter, it is almoft needless to mention brushes and pencils of all fizes as abfolutely neceffary. The brushes are made of boars briftles, or of hair with a mixture of briftles; they ought to be ftraight, very fmooth, and of a round form. Half an hour before they are used, it is proper to foak them in water, in order to fwell the wood of the handle, and prevent the hairs from falling off; after this, they may be applied to all purposes, either in water colours or in oil; but for the former they require lefs foftening. The pencils are made of badgers hair, or any fine hairs, enchafed in the pipes of quills of all fizes. The veffel wherein the pencils are cleaned is made of copper or of tin, fmooth below, rounded at the ends, and divided into two parts by a thin plate in the middle. The oil, or the fubftance with which the pencil is cleaned is contained in one of the divifions. The PALLET is made of the wood of the pear or apple tree, of an oval of fquare shape, very flender, but fomewhat thicker at the centre than at the extremities. A hole is made in one of its fides fufficiently large to admit the thumb of the workman. When the pallet is new, it is covered with oil of walnuts; and as often as it dries, the operation is repeated, till it be fully impregnated; it is afterwards polished, and finally rubbed with a piece of linen dipped in oil of common nuts. The painter's KNIFE is a thin flexible plate, equally flender on both fides, rounded at one extremity, and the other fixed into a handle of wood. All the VESSELS employed to hold the colours fhould be varnified; a precaution neceffary to prevent their drying too quickly. To grind, is to reduce to powder the fubftances which give colours, on a piece of marble or any hard ftone, by means of water, oil, or effence. To dilute, is to impregnate a liquid with a tint in fuch a manner as to make it capable of being applied by a bruth. When the materials are grinded in water, it is proper to dilute them in fize made from parchment. If they are diluted in fpirit of wine, there must be no more diluted than what ferves the immediate occafion, as colours prepared in this manner dry very rapidly. Colours grinded in oil are fometimes diluted with pure oil, more frequently with oil mixed with effence, and commonly with the pure effence of turpentine; the effence makes the colours eafy to work. Thofe prepared in this manner are more fold, but they require more time to dry. When colours are grinded with the effence of tur. pentine, and diluted in varn fh, as they require to be immediately applied, it is neceflary to prepare a fmall quantity at a time. This preparation of colours gives greater brilliancy, and dries more speedily, than those prepared in oil; but they require more art to manage them. Colours, or coloured fubftances, are grinded with a mullet, which is employed on the stone till they become a very fine powder. The ope ration is facilitated by moistening them from time to time with a little water, and by collecting them under the mullet with a knife. They are after. wards laid in small heaps on a fheet of white paper, and allowed to dry in a fituation not expofed to duft. Those who grind white lead have a ftone for the purpose, as this colour is very easily tarnished. In executing this part well, it is ne ceffary to grind the colours equally and moderately; to grind them separately, and not to produce a tint by mixture till the colours are well prepared. Dilute no more at a time than is to be employed, to prevent them from growing thick. In grinding the colours, put in no more liquid than is neceffary to make the folid fubftances yield easily to the mullet: the more the colours are grinded, they mix better, and give a imoother and more agreeable painting. Great attention should be paid to the grinding and diluting of colours, that they may be neither too thick nor too thin. SECT. II. Of the APPLICATION of COLOURS, in GENERAL. 1. PREPARE only the quantity necessary for the work, becaufe they do not keep long; and those which are newly mixed are more vivid and beautiful. 2. Hold the brush straight before you, and allow only the furface to be applied to the subject; if you had it inclined in any other direction, you will run the hazard of painting unequally. 3. It is neceffary to lay on the colours boldly, and with great ftrokes; taking care at the fame time to spread them equally over the furface, and not filling up the moulding and carved work. If this accident fhould happen, you must have a little bruth to clean out the colours. 4. Stir them frequently in the veffel, that they may preferve always the fame tint, and that no fediment may remain at the bottom. 5. Take care not to overcharge the brush with the colour. 6. Never apply a fecond layer till the first or preceding one be perfectly dry; which is easily known, when, in bearing the hand gently over it, it does not adhere. 7. To render this drying more speedy and uniform, make always the layers as thin as poffible. 8. Before painting, prime the subject; that is, give it a layer of fize, or of white colouring oil, to fill up the pores, and render the surface smooth: thus fewer lawyers of colour or of varnish are afterwards neceffary. 9. Every fubject to be painted or gilded ought to have firft a white ground; this preferves the colours fresh and vivid, and repairs the damage which they occafionally receive from the air. Nnnnz SECT. SECT. III, OF PAINTING in WATER-COLOURS. To paint in water-colours, is to do it in thofe which are grinded in water, and diluted in fize. There are three kinds of this painting; viz. the common, the varnished, and that which is called king's awhite. 1. Take care that there be no greafe on the fubject; if there be, scrape it off or clean it with a lye, or rub the greafy part with garlic and wormwood. 2. Let the diluted colour fall in threads from the end of the brush when you take it out of the veffel; if it adheres to it, it is a proof that it wants fize. 3. Let all the layers, especially at the beginning, be laid on very warm, provided the liquid be not boiling, which would effectually spoil the fubject; and, if on wood, expofe it to crack. The fat layer, iven immediately before the varnish, is the only one which ought to be applied cold. 4. In very fine work, where it is neceffary to have beautiful and folid colours, the fubjects are prepared by fize and proper whites, which ferve as a ground to receive the colour, and render the furface very equal and smooth. 5. Whatever colour is to be laid on, the white ground is the beft, as it affimilates moft eafily with the painting, which borrows always fomething of the ground. 6. If knots of wood are found in the subject, it is neceffary to rub them with garlic, to make the fize adhere. To make the following details fufficiently plain, we fhall take the measures to which the quantity of colours are applied at fathoms; that is to fay, fix feet in height by fix feet in breadth. We shall afterwards fix the quantity of materials, and of liquids neceffary to cover this furface. This, however, cannot be exactly defined; as fome fubjects imbibe the colours much more than others, The manner of employing them alfo makes a difference; as habit enables one to manage them to greater advantage than another. The firft layer will confume more than the fecond; and a prepared fubject requires lefs than one which has not been fo. The fathom above-mentioned must be under. flood of a smooth and equal furface; for if the wood is varied with mouldings and carving, there must be a difference in the quantity of colours. In general, it requires about a pound of colours to paint a fquare fathom in water-colours. In making up this quantity, take 3 4ths of colours grinded in water, and 4th ib. or 6 oz. of fize to dilute it. SI Of PAINTING in COMMON WATER COLOURS. Works which require no great care or prep ration, as cielings and staircafes, are generally painted in commoh water-colours; i. e. with earths infufed in water, and diluted in fize. 1. For a common white kind of this painting, eep SPANISH WHITE moderately pounded in water for two hours Infufe a proper quantity of the black of charcoal in water for the fame fpace of time; mix the black and white in the them up with a pretty ftrong fize, fufficiently proportion that the tint requires ; afterwards mix thick and warm, and apply them to the fubject in as many layers as may be thought neceffary. It requires about 2 lb. of white in a pint of water, and a quantity of black in proportion to the tint, together with a part of fize, to cover a fquare fathom. If this be employed on old walls, they must be well feraped, the duft brushed off with a hair befom, and washed carefully with lime water. If on new plafter, the colours require more fize. All kinds of colours may be grinded in water only when the tint is made; and when they have been infufed in water, they must be mixed up with fize. ii. The WHITE DES CARMES is a manner of whitening interior walls, whereby they are rendered extremely beautiful. I. Procure a quantity of the very beft lime, and pass it through fine linen; pour it into a large tub, furnished with a fpigot at the height equal to that which the lime occupies; fill the tub with clear fountain water; beat the mixture with great pieces of wood, and then allow it to fettle for 24 hours. 2. Open the fpigot, allow the water to run off, fupply the tub with fresh water, and continue this operation for feveral days until the lime receives the greatest degree of whiteness. 3. When the water is finally run off, the lime will be found in the confiftency of pafte; but with the quantity ufed, it is neceflary to mix a little Prussian blue or indigo to relieve the brightnefs of the white, and a fmall quantity of turpentine to give it brillianey. The fize proper for it is made of glove-leather, with the addition of fome alum'; and the whole is applied with a strong brush in five or fix layers to new plaster. 4. The wall is ftrongly rubbed over with a brufli of hogs briftles after the painting is dry; which gives it its luftre and value, and which makes it appear like marble or ftucco. iii. BADEGEON is a pale yellow colour applied to plafter, to make it appear like free-ftores. It gives to old houfes and churches the exterior of a new building, by affuming the colour of ftones newly cut. 1. Take a quantity of lime newly kilned. 2. Add to it, the half quantity of what the French call feiure de pierre, in which must be mixed of the ochre of rue, according to the colour of the Rone intended to be imitated. 2. Steep the whole in a pail of water, in which is melted a pound of rock alum. When the feiure de pierre cannot be obtained, use a greater quantity of ochre de rue, or of yellow ochre, or grind the fcales of the ftones de St Leu; pafs it through a fieve; and along with the lime it will form a cement on which the weather will scarcely make any impreffion. iv. When the CIELINGS OF ROOFS of ROOMS are new, ahd you with to whiten them, take white of Bougival, to which add, a little of the black of charcoal to prevent the white from growing reddifh; infufe them feparately in water, mix the whole with half water and half fize of glove-leather, which being ftrong would make the layer come off in rolls if it were not reduced with water. Give two layers of this tint while it is lukewarm. If the roof has been formerly whitened, it is neceffary to fcrape to the quick alt the remaining white; then give it two or three layers of lime to ground and whiten it; brush it carefully over, and give it two or three layers of the white of Bougival prepared as before. v. To COLOUR the BACKS of CHIMNEYS with LEAD ORE, clean them with a very strong brush, and carefully rub off the duft and ruft; pound about a quarter of a pound of lead ore into a fine powder, and put it into a veffel with half a pint of vinegar; then apply it to the back of the chimney with a bruth. When it is made black with this liquid, take a dry brush, dip it in the fame powder without vinegar, and dry and rub it with this brush till it become fhining as glafs. II. Of VARNISHED WATER-COLOURS. The advantages of this kind of painting are, that the colours do not fade; that they reflect the light; that they give no offenfive fmell, but permit the places to be inhabited as soon as finished ; and that the varnih preferves the wood from infects and moisture. To make a fine varnish on water colours, seven principal operations are neceffary; namely to fize the wood, to prepare the white, to foften and rub the fubject, to clean the moulding, to paint, to fize, and to varnish. 1. To fize the wood is to give one or two layers of fize to the fubject intended to be painted. Take three heads of garlic and a handful of wormwood leaves; boil them in three pints of water till they are reduced to one; pafs the juice through a linen cloth, and mix it with a pint of parchment fize; add half a handful of falt and half a pint of vinegar; and boil the whole on the fire. Size the wood with this boiling liquor; allow it to penetrate into the carved and fmooth places of the wood, but take care at the fame time to take it as clean off the work as poffible, or at least to leave it at no place thicker than another. This firft fizing ferves to fill up the pores of the wood, and to prevent the materials afterwards from collecting in a body, which would cause the work to fall off in fcales. In a pint of ftrong parchment fize, to which add four pints of warm water, put two handfuls of white Bougival, and allow it to infufe for half an hour. Stir it well, and give a single layer of it to the subject very warm, but not boifing, equally and regularly laid on, and dafhed with repeated ftrokes of the brush into the mouldings and carved work. 2. To prepare the white, take a quantity of ftrong parchment fize, and sprinkle lightly over it with the band Bougival white, till the fize be covered with it about half an inch in thickness; allow it to foak for half an hour as near the fire as to keep it milk warm; and then stir it with the brush till the lumps are broken, and it be fufficiently mixed. Give 7, 8, or 10 layers of this white, or as many as the nature of the work or the defects of the wood fhall render neceffary, giving more white to the parts which require to be foftened; but, in general, the layers must be equal both with regard to the quantity of the white and the ftrength of the fize. The last layer of the white ought to be made clearer than the rest, by adding water. It must be applied more flightly, taking care with fmall brufhes to cover all the difficult places in the mouldings and carved work. Between the drying of the different layers fill up all the defects with white mastich and fize. 3. To foften, is to give the fubject after the whitening a fmooth and equal surface, and to rub it over with a pumice ftone. The wood being dry, take little pieces of white wood and pumiceftone, grinded for the purpose into all neceffary forms, either for the pannels or the moulding. Take cold water, heat being destructive of this kind of work; in fummer it is common to add a little ice. Soften the wall with a brush, but only as much at a time as you can eafily work, as the water might dilute the white and fpoil the whole Then fmooth and rub it with the pumice ftones and with the small pieces of wood; wash it with a bruth as you fmooth it, and rub it over with a piece of new linen, which gives a fine luftre to the work. 4. The mouldings and carved work are cleaned with an iron; and the, only thing to be attended to in the operation is not to raise the grain of the wood. 5. The fubject thus prepared is ready to receive the colour intended to be given it. Choose your tint; fuppofe a filver colour. Grind white crufe and Bougival white feparately in water, of each an equal quantity, and mix them together. Add a little blue of indigo and a very fmall quantity of black of charcoal from the vine tree very fine, grinded alfo separately, and in water; more or lefs of the one or other gives the tint required. Dilute this tint in ftrong parchment fize; país it through a bolting cloth of filk very fine, and lay the tint on the work, taking care to spread it very equally; and then give it two layers, and the colour is applied. 6. Make a weak, beautiful, and clean fize; ftir it till it cools; strain it through a fine cloth, and give two layers to the work with a foft painting brush, which has been used, but carefully cleaned. Take care not to choak up the mouldings, nor to lay on the fize thicker in one place than another, and spread it over the work very flightly, otherwise you will dilute the colours, and occafion undulations in the painting. The beauty of the work depends on this laft fizing; for if any part, is omitted, the varnish will penetrate into the colours and give it a darker fhade. 7. When the fizing is dry, lay on two or three layers of fpirit-of-wine varnish, taking care that the place on which you lay it be warm, and the work is finished. III. Of the KING'S WHITE. THIS derives its name from the use of it in the apartments of the late French king. It is in all refpects conducted like the former, except that there is only a fmall quantity of indigo, to take the yellow from the white, without any black of charcoal, and without varnish. This white anfwers extremely well for apartments which are feldom ufed; but otherwife it fpoils cafily, especially in bed-chambers. It is the beft white where there is any kind of gilding; and in this case it receives a little varnish. SECT, |