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]