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]]
CHAPTER XI. (XXV.)
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]]