In the same manner the colours should be employed with so much harmony that a dark and a light are not left unpleasantly contrasted in light and shade, so as to create a discordance and a disagreeable lack of unity, save only in the case of the projections, which are those shadows that the figures throw one on to the other, when a ray of light strikes on a principal figure, and makes it darken the second with its projected shadow. And these again when they occur must be painted with sweetness and harmony, because he who throws them into disorder makes that picture look like a coloured carpet or a handful of playing cards, rather than blended flesh or soft clothing or other things that are light, delicate, and sweet. For as the ear remains offended by a strain of music that is noisy, jarring or hard—save however in certain places and times, as I said of the strong shadows—so the eye is offended by colours that are overcharged or crude. As the too fiery mars the design; so the dim, sallow, flat, and over-delicate makes a thing appear quenched, old, and smoke-dried; but the concord that is established between the fiery and the flat tone is perfect and delights the eye just as harmonious and subtle music delights the ear. Certain parts of the figures must be lost in the obscure tints and in the background of the group; for, if these parts were to appear too vivid and fiery, they would confound the distinction between the figures, but by remaining dark and hazy almost as background they give even greater force to the others which are in front. Nor can one believe how much grace and beauty is given to the work by varying the colours of the flesh, making the complexion of the young fresher than that of the old, giving to the middle-aged a tint between a brick-colour and a greenish yellow; and almost in the same way as in drawing one contrasts the mien of the old with that of youths and young girls and children, so the sight of one face soft and plump, and another fresh and blooming, makes in the painting a most harmonious dissonance.
In this way one ought, in working, to put the dark tints where they are least conspicuous and make least division, in order to bring out the figures, as is seen in the pictures of Raffaello da Urbino and of other excellent painters who have followed this manner. One ought not however to hold to this rule in the groups where the lights imitate those of the sun and moon or of fires or bright things at night, because these effects are produced by means of hard and sharp contrasts as happens in life. And in the upper part, wherever such a light may strike there will always be sweetness and harmony. One can recognize in those pictures which possess these qualities that the intelligence of the painter has by the harmony of his colours assured the excellence of the design, given charm to the picture, and prominence and stupendous force to the figures.
CHAPTER V. (XIX.)
Of Painting on the Wall, how it is done, and why it is called Working in Fresco.
§ 81. The Fresco process.
Of all the methods that painters employ, painting on the wall is the most masterly and beautiful, because it consists in doing in a single day that which, in the other methods, may be retouched day after day, over the work already done. Fresco was much used among the ancients,[[196]] and the older masters among the moderns have continued to employ it. It is worked on the plaster while it is fresh and must not be left till the day’s portion is finished. The reason is that if there be any delay in painting, the plaster forms a certain slight crust whether from heat or cold or currents of air or frost whereby the whole work is stained and grows mouldy. To prevent this the wall that is to be painted must be kept continually moist; and the colours employed thereon must all be of earths and not metallic and the white of calcined travertine.[[197]] There is needed also a hand that is dexterous, resolute and rapid, but most of all a sound and perfect judgement; because while the wall is wet the colours show up in one fashion, and afterwards when dry they are no longer the same. Therefore in these works done in fresco it is necessary that the judgement of the painter should play a more important part than his drawing, and that he should have for his guide the very greatest experience, it being supremely difficult to bring fresco work to perfection. Many of our artists excel in the other kinds of work, that is, in oil or in tempera, but in this do not succeed, fresco being truly the most manly, most certain, most resolute and durable of all the other methods, and as time goes on it continually acquires infinitely more beauty and harmony than do the others. Exposed to the air fresco throws off all impurities, water does not penetrate it, and it resists anything that would injure it. But beware of having to retouch it with colours that contain size prepared from parchment, or the yolk of egg, or gum or tragacanth, as many painters do, for besides preventing the wall from showing up the work in all clearness, the colours become clouded by that retouching and in a short time turn black. Therefore let those who desire to work on the wall work boldly in fresco and not retouch in the dry, because, besides being a very poor thing in itself, it renders the life of the pictures short, as has been said in another place.
CHAPTER VI. (XX.)
Of Painting in Tempera,[[198]] or with egg, on Panel or Canvas, and how it is employed on the wall which is dry.
§ 82. Painting in Tempera.
Before the time of Cimabue and from that time onwards, works done by the Greeks in tempera on panel and occasionally on the wall have always been seen. And these old masters when they laid the gesso ground on their panels, fearing lest they should open at the joints, were accustomed to cover them all over with linen cloth attached with glue of parchment shreds, and then above that they put on the gesso to make their working ground.[[199]] They then mixed the colours they were going to use with the yolk of an egg or tempera,[[200]] of the following kind. They whisked up an egg and shredded into it a tender branch of a fig tree, in order that the milk of this with the egg should make the tempera of the colours, which after being mixed with this medium were ready for use. They chose for these panels mineral colours of which some are made by the chemists and some found in the mines. And for this kind of work all pigments are good, except the white used for work on walls made with lime, for that is too strong. In this manner their works and their pictures are executed, and this they call colouring in tempera. But the blues are mixed with parchment size, because the yellow of the egg would turn them green whereas size does not affect them, nor does gum. The same method is followed on panels whether with or without a gesso ground; and thus on walls when they are dry the artist gives one or two coats of hot size, and afterwards with colours mixed with that size he carries out the whole work. The process of mixing colours with size is easy if what has been related of tempera be observed. Nor will the colours suffer for this since there are yet seen things in tempera by our old masters which have been preserved in great beauty and freshness for hundreds of years.[[201]] And certainly one still sees things of Giotto’s, some even on panel, that have already lasted two hundred years and are preserved in very good condition. Working in oil has come later, and this has made many put aside the method of tempera: in so much that to-day we see that the oil medium has been, and still is, continually used for panel pictures and other works of importance.