Vasari on technique

Of painting in Oil on Stone, and what stones are good for the purpose.

§ 89. Oil painting on Stone.

The courage of our pictorial artists has gone on increasing, so that colouring in oil, besides the use made of it on the wall, can when they desire be employed also for painting on stones. Of these last they have found a suitable kind on the sea coast of Genoa, in those flagstones we have spoken of in connection with Architecture,^[222] which are very well fitted for this purpose, for the reason that they are compact and of fine grain, and take an even polish. In modern times an almost unlimited number of artists have painted on these slabs and have found the true method of working upon them. Later they have tried the finer stones, such as marble breccias, serpentines, porphyries and the like, which being smooth and polished admit of the colour attaching itself to them. But in truth when the stone is rough and dry it imbibes and takes the boiled oil and the colour much better; as is the case with some kinds of soft peperino, which, when they are worked over the surface with an iron tool and are not rubbed down with sand or a piece of hearth stone, can be brought to a smooth surface with the same mixture that I spoke of in connection with the rough cast and that heated trowel. Therefore it is not necessary to begin by spreading size on all these stones, but only a coat of priming of oil colour, that is, the composition already referred to, and when this is dry the work may be begun at will.

He who desires to paint a picture in oil on stone can take some of those Genoese flagstones and have them cut square and fixed in the wall with clamps over a layer of stucco, spreading the composition well over the joinings so as to make a flat surface of the size the artist needs. This is the true way of bringing such works to a finished state, and when completed, ornaments can be added of fine stones, breccias, and other marbles. These, provided they are worked with diligence and care, endure for ever. They may or may not be varnished, just as you like, because the stone does not suck up, that is, absorb as much as does the panel or canvas, and it is impervious to worms, which cannot be said for wooden panels.^[223]

Of Painting on the wall in Monochrome with various earths; how objects in bronze are imitated; and of groups for Triumphal Arches or festal structures, done with powdered earths mixed with size, which process is called Gouache and Tempera.

§ 90. Imitative Paintings for Decorations.

Monochromes according to the painters are a kind of picture that has a closer relation to drawing than to work in colour because it has been derived from copying marble statues and figures in bronze and various sorts of stone; and artists have been accustomed to decorate in monochrome the façades of palaces and houses, giving these a semblance other than the reality, and making them appear to be built of marble or stone, with the decorative groups actually carved in relief; or indeed they may imitate particular sorts of marble, and porphyry, serpentine, and red and grey granite or other stones, or bronze, according to their taste, arranging them in many divisions; and this style is much in use now-a-days for the fronts of houses and palaces in Rome and throughout Italy.

These paintings are executed in two ways, first, in fresco which is the true way; secondly, on canvas to adorn arches erected on the occasion of the entrance of princes into the city, and of processions, or in the apparatus for fêtes and plays, since on such structures they produce a very beautiful effect. We shall first treat of the manner of working these in fresco, and then speak of the other method. In the first kind the backgrounds are laid in with potters’ clay, and with this is mixed powdered charcoal or other black for the darker shadows, and white of travertine. There are many gradations from light to dark; the high lights are put in with pure white, and the strongest shadows are finished with the deepest black. Such works must have boldness, intention, power, vivacity, and grace, and must be expressed with an artistic freedom and spirit and with nothing cramped about them, because they have to be seen and recognized from a distance.^[224] In this style too must bronze figures be imitated; they are sketched in on a background of yellow and red earth, the darker shades put in with blended tints of black, red, and yellow, the middle tints with pure yellow, and the high lights with yellow and white.^[225] And with these painters have composed decorations on the façades, intermingling statues, which in this kind of work give a most graceful effect.

Those pictures however intended for arches, plays, or festivals, are worked after the canvas has been prepared with clay, that is, with that pure earth (terretta) before mentioned which potters use, mixed with size,^[226] and the back of the canvas must be moistened while the artist is painting on it, that the darks and lights of his work may unite better with the ground of clay.^[227] It is customary to mix the blacks with a little tempera;^[228] white leads are used for the white, and red lead to simulate relief in things that appear to be of bronze, and Naples yellow (giallino) to put in the high lights over the red lead, and for the backgrounds and the darks the same red and yellow earths and the same blacks that I spoke of in connection with fresco work; these make the half tints and shadows. The painter uses also other different pigments to shade other kinds of monochromes, such as umber to which is added terra verte and yellow ochre and white; in the same way is used black earth, which is another sort of terra verte and the dark colour that is called ‘verdaccio.’^[229]

Of the Sgraffiti for house decoration which withstand water; that which is used in their production; and how Grotesques are worked on the wall.

§ 91. Sgraffito-work.

Painters have another sort of picture which is drawing and painting both together. This is called sgraffito; it serves only for ornament on the façades of houses and palaces, and is very quickly executed, while it perfectly resists the action of water, because all the outlines, instead of being drawn with charcoal or other similar material, are etched by the hand of the painter with an iron tool. The work is done in this manner. They take lime mixed with sand in the usual fashion and tinge it by means of burnt straw to a tint of a medium colour inclining to pearl grey, a little more towards the dark than the middle tint, and with this they plaster the façade. That done and the façade smoothed, they give it a coat of white all over with the white lime of travertine, and then dust over the (perforated) cartoons, or else draw directly that which they wish to execute. Afterwards pressing upon it with an iron stylus they trace the contours and draw lines on the cement, which, because there is a black substance underneath, shows all the scratches of the tool as marks of drawing.^[230]

It is customary too to scrape away the white in the backgrounds, and then to prepare a water colour tint, darkish and very watery, and with that reinforce the darks, as one would do on paper; this seen at a distance is most effective. But if there be grotesques or leafage in the design, cast shadows are painted on the background by means of that water colour. This is the work that the painters have called sgraffito, on account of its being scratched by the iron instrument.

§ 92. Grotesques, or Fanciful Devices, painted or modelled on Walls.^[231]

There remains to us now to speak of the grotesques done on the wall. For those, then, that go on a white ground, when the background is not of stucco (white plaster), because the ordinary lime plastering is not white, therefore a thin coat of white is laid over; and that done the cartoons are powdered and the work executed in fresco with opaque colours,^[232] but these will never have the charm of those worked directly upon the stucco. In this style there may be grotesques both coarse and fine, and these are done in the same way as the figures in fresco or on the dry wall.

How Grotesques are worked on the Stucco.

The grotesque is a kind of free and humorous picture produced by the ancients for the decoration of vacant spaces in some position where only things placed high up are suitable. For this purpose they fashioned monsters deformed by a freak of nature or by the whim and fancy of the workers, who in these grotesque pictures make things outside of any rule, attaching to the finest thread a weight that it cannot support, to a horse legs of leaves, to a man the legs of a crane, and similar follies and nonsense without end.^[233] He whose imagination ran the most oddly, was held to be the most able. Afterwards the grotesques were reduced to rule and for friezes and compartments had a most admirable effect. Similar works in stucco were mingled with the painting. So generally was this usage adopted that in Rome and in every place where the Romans settled there is some vestige of it still preserved. And truly, when touched with gold and modelled in stucco such works are gay and delightful to behold.

They are executed in four different ways.^[234] One is to work in stucco alone: another to make only the ornaments of stucco and paint groups in the spaces thus formed and grotesques on the friezes: the third to make the figures partly in stucco, and partly painted in black and white so as to imitate cameos and other stones. Many examples of this kind of grotesque and stucco work have been, and still are seen, done by the moderns, who with consummate grace and beauty have ornamented the most notable buildings of all Italy, so that the ancients are left far behind. Finally the last method is to work upon stucco with water colour, leaving the stucco itself for the lights, and shading the rest with various colours. Of all these kinds of work, all of which offer a good resistance to time, antique examples are seen in numberless places in Rome, and at Pozzuoli near to Naples. This last sort can also be excellently worked in fresco with opaque colours, leaving the stucco white for the background.^[235] And truly all these works possess wonderful beauty and grace. Among them are introduced landscape views, which much enliven them, as do also little coloured compositions of figures on a small scale. There are to-day many masters in Italy who make this sort of work their profession, and really excel in it.

and other methods.

§ 93. Methods of Gilding.

It was truly a most beautiful secret and an ingenious investigation—that discovery of the method of beating gold into such thin leaves, that for every thousand pieces beaten to the size of the eighth of a braccio in every direction, the cost, counting the labour and the gold, was not more than the value of six scudi.^[238] Nor was it in any way less ingenious to discover the method of spreading the gold over the gesso in such a manner that the wood and other material hidden beneath it should appear a mass of gold. This is how it is done. The wood is covered with the thinnest gesso kneaded with size weak rather than strong, and coarser gesso is laid on in several coats according as the wood has been well or badly prepared. When the gesso is scraped and smoothed, white of egg beaten carefully in water is mixed with Armenian bole, which has been reduced with water to the finest paste. The first coat of this is made watery, I mean to say liquid and clear, and the next thicker. This is laid on to the panel at least three times, until it takes it well all over, then with a brush the worker gradually wets with pure water the parts where the Armenian bole has been applied and there he puts on the gold leaf, which quickly sticks to that soft substance;^[239] and when partially but not entirely dry he burnishes it with a dog’s tooth or the tooth of a wolf in order to make it become lustrous and beautiful.^[240]

Gilding is effected in another fashion also, ‘with a mordant,’ as it is said.^[241] This is used for every sort of material—stone, wood, canvas, metals of all kinds, cloth, and leather; and is not burnished as is the former. The mordant, which is the lye that holds the gold, is made of various sorts of drying oil pigments and of oil boiled with the varnish in it. It is laid upon the wood which has first received two coats of size. And after the mordant is so applied, not when it is fresh, but half dry, the gold leaf is laid upon it. The same can be done also with gum-ammoniac, when there is hurry, provided that the stuff is good. This is used more to adorn saddles and make arabesques and other ornaments than for anything else. Sometimes also gold leaves are ground in a glass cup with a little honey and gum^[242] and made use of by miniature-painters and many others who, with the brush, delight to draw outlines and put very delicate lights into pictures. And all these are most valuable secrets; but because they are very numerous one does not take much account of them.

Of Glass Mosaic and how it is recognized as good and praiseworthy.

§ 94. Glass Mosaics.

We have spoken sufficiently above, in the sixth chapter on Architecture, of the nature of mosaic and how it is made, and, adding here just so much as really refers to pictures, let us say that very great mastery is needed to arrange the pieces so harmoniously that the mosaic appears at a distance a genuine and beautiful picture, seeing that this kind of work demands great experience and judgement and a profound knowledge of the art of design. For if any one in his designs obscure the mosaic with too great wealth and abundance of figures in the groups, and with multiplying over-much the pieces, he will bring it all into confusion. Therefore the design of the cartoons made for mosaic must be open, broad, easy, clear, and carried out with excellence and in admirable style.^[243] The artist who understands the force of shadows in the design and of giving few lights and many darks, leaving in these certain vacant spaces or fields, he above all others will make his mosaic beautiful and well arranged. Mosaic to be praised must have clearness in itself, with a certain harmonious obscurity towards the shadows, and must be executed far from the eye with the greatest discretion that it may be esteemed painting and not inlaid work.^[244] Therefore the mosaics that have these qualities, are good and will be praised by everyone; and it is certain that mosaic is the most durable picture that exists. Other painting fades through time, but mosaic continually brightens with age; other painting fails and wastes away, while mosaic on account of its long life may almost be called eternal.^[245] For this reason we perceive in it not only the perfection of the old masters, but also of the ancients^[246]—by means of those examples from their epoch that we recognize as such to-day, as in the Temple of Bacchus at Sant’ Agnese outside of Rome, where all that is there executed is exceedingly well done.^[247] At Ravenna also there is some very beautiful old mosaic in many places, and at Venice in San Marco, at Pisa in the Duomo, and at Florence in the tribune of San Giovanni,^[248] but the most beautiful of all is that of Giotto in the main aisle of the porch at St. Peter’s at Rome^[249]—truly a miraculous thing in that kind of work—and among the moderns there is that of Domenico Ghirlandaio above the door outside Santa Maria del Fiore that leads to the Annunziata.^[250]

§ 95. The Preparation of the Mosaic Cubes.

The pieces for mosaic are prepared in the following manner. When the glass furnaces are ready and the pans full of glass, the workers go round giving to every pan its own colour, starting from a true white which contains body and is not transparent, and carefully proceeding to the darker tints by gradual transitions, in the same manner as they make the mixtures of colours for ordinary painting. Afterwards when the glass is fused and in a fit state, and the mixtures both light and dark and of every tint are prepared, they ladle out the hot glass with certain long iron spoons and spread it on a flat piece of marble, then with another piece of marble press it evenly, making round discs that come equally flat and remain the third part of the breadth of a finger in thickness. Then some cut little square pieces with an iron tool called dog’s mouth, and others break it with a hot iron tool, cracking it as they wish.^[251] The same pieces if too long are cut with emery and so are all the pieces of glass that have need of it. They are then put into boxes and kept arranged as is done with the pigments for fresco work, which are kept separately in various little pots so that the mixtures of the lighter and the darker tints may be ready at hand for working.

There is another sort of glass covered with gold that is used for the background and for the lights of the draperies.^[252] When the glass is to be gilded, the workers take the glass disc which they have made, and damp it over with gum-water, and then apply the gold leaf; this done they put this gold-covered disc on an iron shovel and that in the mouth of the furnace, first covering with a thin piece of glass all the glass disc that they had coated with gold. These coverings are made either of glass bubbles or of broken bottles so that one piece covers the whole disc, and it is then held in the furnace till it becomes almost red, and quickly drawn out, when the gold at once becomes admirably set so as to be imprinted in the glass and remain there. This is impervious to water and resists every attack, and afterwards the disc is cut and disposed as the other coloured pieces described above.

§ 96. The Fixing of the Mosaic Cubes.

In order to fix the mosaic in the wall, the custom is to make a coloured cartoon, though some make it without colour, and to trace or mark the cartoon bit by bit on the stucco,^[253] and then to proceed to arrange the pieces as many as are needed to fill in the mosaic work. The stucco, when put on in a thick coat over the wall, remains available two days and sometimes four, according to the kind of weather. It is made of travertine, lime,^[254] pounded brick, gum-tragacanth and white of egg, and once made it is kept moist with damp cloths. Thus then, bit by bit, they cut the cartoons for the wall, and trace the design on the stucco; afterwards with certain little tongs, they pick up the bits of vitreous paste and fit them together in the stucco, and give lights to the lights, middle tints to the middle tints and darks to the darks, imitating minutely the shadows, the lights, and the half tints as they are in the cartoons.^[255] Thus, working with diligence they gradually bring it all to perfection, and he who best succeeds in joining it so that it comes out even and smooth, is most worthy of praise and is more esteemed than the others. Some are so clever in working mosaic that they make it appear as if painted in fresco. So firmly does the glass harden into the stucco, after the latter has set, that this mosaic lasts for ever—as is testified by the antique mosaics, which are in Rome, and those also which are of the older (modern) times. In both methods of working the moderns of our days have done marvellous things.

Concerning the Compositions and Figures made in Inlaid Work on Pavements in imitation of objects in monochrome.

§ 97. Pavements in Marble Mosaic and Monochrome.

To the mosaic in small pieces our modern masters have added another kind of mosaic, that of marbles fitted together to counterfeit painted groups in monochrome. This art takes its origin from the very ardent desire that there should remain in the world to those who come after, even if other kinds of painting were to be destroyed, a light that may keep alive the memory of modern painters. Hence they have produced with wondrous skill very large compositions that can be placed not only on the pavements, where one walks, but also on the face of walls and palaces, with such beautiful and marvellous art that there can be no danger lest time should waste away the design of those who excel in this profession. Examples of these works can be seen in the Duomo at Siena begun first by Duccio of Siena, then added to by Domenico Beccafumi, and continued by others even to our own day.^[256]

This art possesses so much that is good, new, and durable, that for pictorial work made up of black and white greater excellence and beauty can hardly be desired. It is composed of three sorts of marble, which come from the Carrara mountains:^[257] one of these is the finest pure white marble; another is not white but inclines to a livid tint, which furnishes a middle shade; and the third is grey marble that inclines towards a silvery hue, and this serves for dark. When the artist wishes to compose a figure from these marbles he first prepares a cartoon in light and shade with the same tints, and that done, following the outlines of those medium and dark and pale tints, he fits together with great care in their proper places first of all in the middle, the light of that pure white marble, and then the half-tones and the darks beside them, according to the actual outlines that the artist has drawn in the cartoon. When all the pieces of marble, the light pieces as well as the darks and half tints, are joined together and are laid quite flat, the artist who has prepared the cartoon takes a fine brush dipped in moist black, and, with all the work fitted together before him on the ground, traces in lines the contours and where the shadows come, in the same manner in which one would prepare an outlined drawing for monochrome. That done the carver proceeds to cut in with chisels all those lines and contours that the painter has made, and he hollows out all that part which the brush has marked with black. Having finished this, the pieces are built in on the flat bit by bit, and then with a mixture of boiled black pitch, or asphalt, or black earth, all the hollows which the chisel has made are filled up. When the material is cold and has set, the worker proceeds to remove and rub away the projecting parts with pieces of soft stone, and to smooth and polish with sand, bricks, and water, till all that remains is brought to a true surface, that is, the marble itself and the substance put in to fill up the hollows. When that is done the work remains in aspect exactly like a flat picture, and possesses great force combined with art and masterly skill. This kind of work has come much into use on account of its beauty.

§ 98. Pavements in Variegated Tiles.

Hence it is that the pavements of many apartments in our day are made of variegated bricks, one portion of white clay, that is of clay that draws towards a bluish shade when it is fresh and when baked becomes white, and the other portion of the ordinary earth for making bricks which becomes red when baked. Of these two sorts are made pavements, inlaid in various designs and compartments, as the papal halls at Rome in the time of Raffaello da Urbino bear testimony;^[258] and now recently many apartments in the castle of Sant’ Angelo where emblems of lilies of fitted pieces showing the arms of Pope Paolo, and many other devices, have been made with these same bricks. In Florence also there is the pavement of the library of San Lorenzo ordered to be made by Duke Cosimo. All have been executed with such great care that anything more beautiful in that sort of workmanship cannot be desired, and the point of departure for all these inlaid things was the first mosaic.

§ 99. Pavements in Breccia Marble.

To explain why no mention was made of some breccias recently discovered by Duke Cosimo while stones and marbles of all sorts were being spoken of—I may say that in the year 1563 His Excellency found in the mountains of Pietrasanta, near to the village of Stazzema, a hill which extends for two miles, whose outer crust is of white marble excellent for statues. The under layer is a red and yellowish breccia, and those farther down are greenish, black, red, and yellow with various other mixtures of colour; all these marbles are hard, and their nature is such that the farther one penetrates inwards the greater is their solidity. Up to the present time there can be seen quarried from thence columns of fifteen to twenty braccia; but these marbles are not yet put into use, because a road three miles in length is only now being constructed by order of his Excellency to make it possible to transport the marbles from the said quarries to the sea shore.^[259] These breccias will, so far as one can see, be most suitable for pavements.

Of Mosaic in wood, that is, of Tarsia; and of the Compositions that are made in Tinted Woods, fitted together after the manner of a picture.

§ 100. Inlays in Wood.

How easy a thing it is to add some new discovery to the inventions of the past, is clearly shown to us, not only by the aforesaid fitted pavement, which without doubt comes from mosaic work, but also by these same tarsias and the figures of many different things, that closely resembling mosaic and painting have been made by our elder artists out of little pieces of wood, variously coloured, fitted and joined together in panels of walnut. This is called by the moderns ‘lavoro di commesso’ (inlaid work) although to the elder artists it was tarsia. The best specimens of this work were to be found in Florence in the time of Filippo di Ser Brunellesco and afterwards in that of Benedetto da Maiano, who, however, strangely enough judged tarsia a useless thing and completely abandoned it as will be told in his Life. He, like the others of past times, executed tarsia in black and white only, but Fra Giovanni of Verona who was very proficient in the art improved it greatly, giving various colours to the woods by means of dyes in boiling water and of penetrating oils, in order to produce the lights and shadows with these variously tinted woods, as in the art of painting, and skilfully putting in the high lights by means of the very white wood of the silio.^[260] This work began in the first instance with designs in perspective, because the forms in these end with plane angles, and the pieces joined together showed the contours, and the work appeared all of one flat piece, though it was made up of more than a thousand. The ancients worked however in the same manner with incrustations of fine stones: as is plainly seen in the portico of St. Peter’s, where there is a cage with a bird and all the details of the wooden bars etc., on a ground of porphyry inlaid with other different stones.^[261] But, because wood is more pliant and much more amenable for this work, our masters have been able to make more abundant use of it and in the way that best pleased them. Formerly for making the shadows they used to scorch the wood with fire on one side, this imitated shade well; but others afterwards have used oil of sulphur and corrosive sublimate and preparations of arsenic, with which substances they have obtained the hues that they desired, as is seen in the work of Fra Damiano in San Domenico in Bologna.^[262] And because such a line of work consists only in the choice of designs that may be adapted to it—those containing blocks of buildings and objects with rectangular outlines to which force and projection can be lent by means of light and shade—it has always been exercised by persons possessing more patience than skill in design. And thus it is that though many things have been produced in this line, such as representations of figures, fruit, and animals, some of which are in truth most life-like, yet since it is a work that soon becomes black and does not do more than counterfeit painting, being less than painting, and is also of short duration because of worms and fire, it is considered time thrown away in vain to practise it, although it may indeed be both praiseworthy and masterly.^[263]

On Painting Glass Windows and how they are put together with Leads and supported with Irons so as not to interfere with the view of the figures.

§ 101. Stained Glass Windows; their Origin and History.

Formerly the ancients were in the habit of filling in their windows, but only in the houses of great men, or of those at least of some importance, in such a manner as to prevent the wind or cold from entering, while not excluding the light. This plan was adopted only in their baths and sweating rooms, vapour baths and other retiring rooms, and the apertures and vacant places of these were closed with transparent stones, such as onyx marbles,^[264] alabasters, and other delicate marbles that are variegated or that incline towards a yellowish tint. But the moderns, who have had glass furnaces in much greater abundance, have made the windows of glass, either of bull’s-eyes^[265] or of panes, similar to or in imitation of those that the ancients made of stone; and they have fastened them together and bound them with strips of lead, grooved on both sides, and furnished them and secured them with irons let into the walls for this purpose, or indeed into wooden frames,^[266] as we shall relate. Whereas at first the windows used to be made simply of clear bull’s-eyes with white or coloured corners, afterwards the artists thought of making a mosaic of the shapes of these glasses differently coloured and joined after the manner of a picture.^[267] And so refined has the skill in this art become, that in our days glass windows are seen carried to the same perfection that is arrived at in fine pictures upon panel, with all their harmony of colour and finish of execution, and this we shall amply show in the Life of the Frenchman Guglielmo da Marcilla.^[268]

In this art the Flemings and the French have succeeded better than the other nations, seeing that they, with their cunning researches into pigments and the action on them of fire, have managed to burn in the colours that are put on the glass, so that wind, air, and rain may do them no injury, whereas formerly it was customary to paint windows in colours coated with gum and other temperas that wasted away through time and were carried off by the winds, mists, and rains, till nothing was left but the mere colour of the glass. In the present age, we see this art brought to that high grade beyond which one can hardly desire further perfection of fineness and beauty and of every quality which contributes thereto. It supplies a delicate loveliness not less beneficial to health, through securing the rooms from wind and foul airs, than useful and convenient on account of the clear and unimpeded light that by its means is offered to us.

In order to produce such windows, three things are necessary, namely, luminous transparency in the glasses chosen,^[269] beautiful arrangement in that which is worked out with them, and clear colour without any confusion. Transparency is secured by knowing how to choose glasses that are clear in themselves, and in this respect French, Flemish, and English glasses are better than the Venetian,^[270] because the Flemish are very clear and the Venetian much charged with colour. In clear glasses when shaded with darker tints the light is not totally lost, they are transparent even in their shadows, but the Venetian, being obscure in their nature and darker still in their shadow, lose all transparency. Again many delight in having the glasses loaded with colours artificially laid on so that when the air and sun strike upon them, they exhibit I cannot tell how much more beauty than do the natural colours; nevertheless, it is better to have the glasses clear in their own substance, rather than obscure, so that when heavily coloured they may not be left too dim.

§ 102. The Technique of the Stained Glass Window.^[271]

For painting on glass, we must first have a cartoon on which are drawn the outlines of the figures and of the folds of the drapery. These show where the pieces of glass have to be joined; then the bits of red, yellow, blue, and white glass must be picked out and divided according to the design for the flesh parts and for the draperies, as occasion demands. To bring each piece of glass to the dimensions traced on the cartoon, the said pieces are laid on the cartoon and the outline marked with a brush dipped in white lead, and to each piece is assigned its number in order to find it easily when joining them together; when the work is finished the numbers are rubbed off. When this is done, in order to cut the pieces to measure, the workman, having first drawn an emery point over the upper surface of the glass along the outline, which he damps with saliva, takes a red-hot pointed tool and proceeds to pass the point along the outlines, keeping a little within them; as he gradually moves the tool, the glass cracks and snaps off from the sheet. Then with the emery point he trims the said pieces, removing the superfluous part, and with a tool called ‘grisatoio’ or ‘topo’ (grozing iron) which nibbles the traced edges, he makes them exact and ready to be joined all round.

In this manner then the bits of glass fitted together are spread on a flat table above the cartoon, and the artist begins to paint in the shadows over the draperies, using for this the ground scales of iron and of another rust^[272] found in iron pits, which is red, or else hard red haematite finely ground, and with these pigments he shades the flesh, using alternately black and red, according to need. To produce the flesh tints it is necessary to glaze all the glasses with this red, and the draperies with the black, the colours being tempered with gum,^[273] and so gradually to paint and shade the glasses to correspond with the tints on the cartoon. When this process is finished, the worker, desiring to put in the brightest lights, takes a short thin brush of hog’s bristles and with it scratches the glass over the light, and removes some of that coat of the first colour that had been given all over, and with the handle of the brush picks out the lights on the hair, the beard, the drapery, the buildings, and the landscapes as he sees fit. There are great difficulties however in this work; and he who delights in it may put various colours on the glass, for example, if he trace a leaf or other minute object over a red colour, intending it to come out in the fire a different tint, he removes from the glass a scale the size of the leaf, with the point of a tool that pares away the upper surface of the glass. This must be the first layer and not more; by so doing, the glass remains white^[274] and can be tinged afterwards with that red^[275] made of many mixtures, which when fused by heat becomes yellow. This can be done with all the colours, but the yellow succeeds better on white than on other colours; when blue is used to paint in the ground, it becomes green in the firing, because yellow and blue mixed make a green colour. This yellow is never used unless at the back of the glass where it is not painted,^[276] because if it were on the face it would mingle and run, so as to spoil and mix itself with the painting; when fired however the whole of the red remains on the surface, this, when scraped away by a tool leaves the yellow visible.^[277]

After the glasses are painted they must be put into an iron muffle with a layer of sifted cinders mixed with burnt lime, and arranged evenly, layer by layer, each layer covered with these ashes; they are then put into the furnace, in which at a slow fire they are gradually heated through till both cinders and glasses begin to glow, when the colours thereon become red hot and run and are incorporated with the glass. In this firing the greatest care must be taken, because a too violent heat would make the glasses crack and too little would not fix the colours. Nor must they be taken out till the pan, or muffle, in which they are placed is seen to be red hot, as well as the ashes, with some samples laid on the top to show when the pigment is liquefied.

After this the leads are cast in certain moulds of stone or iron. The leads have two grooves; that is one on either side, within which the glass is fitted and pressed tight.^[278] The leads are then flattened and made straight and fastened together on a table. Bit by bit all the work is leaded in many squares and all the joinings of the lead soldered by means of tin soldering irons. Across it in parts are iron rods bearing copper wires leaded in to support and bind the work, which has an armature of irons that do not run straight across the figures, but are twisted according to the lines of the joinings, so as not to interrupt the view of the figures. These are rivetted into the irons that support the whole, and they are made not square but round that they may interfere less with the view. They are put on to the outside of the windows and leaded into holes in the walls, and are strongly bound together with copper wires, that are soldered by means of fire into the leads of the windows. And in order that boys and other nuisances should not spoil the windows, a fine network of copper-wire is placed behind them. These works, if it were not for the too fragile material, would last in the world an infinite time. But for all this it cannot be said that the art is not difficult, artistic, and most beautiful.