In all these instances it will be seen that there is no allusion to the immixture of varnishes with the solid colours, except in painting on walls in oil, and that the processes of distemper and oil are always considered as separate arts.[26] On the other hand, the prohibition of Boschini cannot be understood to be universal, for it is quite certain that the Venetians varnished their pictures when done.[27] After Titian had finished his whole-length portrait of Pope Paul III. it was placed in the sun to be varnished.[28] Again, in the archives of the church of S. Niccolo at Treviso a sum is noted (Sept. 21, 1521 ), "per far la vernise da invernisar la Pala dell' altar grando," and the same day a second entry appears of a payment to a painter, "per esser venuto a dar la vernise alla Pala," &c.[29] It is to be observed that in both these cases the pictures were varnished as soon as done;[30] the varnish employed was perhaps the thin compound of naphtha (oglio di sasso) and melted turpentine (oglio d'abezzo), described by Borghini, and after him by Armenini: the last-named writer remarks that he had seen this varnish used by the best painters in Lombardy, and had heard that it was preferred by Correggio. The consequence of this immediate varnishing may have been that the warm resinous liquid, whatever it was, became united with the colours, and thus at a future time the pigment may have acquired a consistency capable of resisting the ordinary solvents. Not only was the surface of the picture required to be warm, but the varnish was applied soon after it was taken from the fire.[31]
Many of the treatises above quoted contain directions for making the colours dry:[32] some of these recipes, and many in addition, are to be found in Palomino, who, however defective as an historian,[33] has left very copious practical details, evidently of ancient date. His drying recipes are numerous, and although sugar of lead does not appear, cardenillo (verdigris), which is perhaps as objectionable, is admitted to be the best of all dryers. It may excite some surprise that the Spanish painters should have bestowed so much attention on this subject in a climate like theirs, but the rapidity of their execution must have often required such an assistance.[34]
One circumstance alluded to by Palomino, in his very minute practical directions, deserves to be mentioned. After saying what colours should be preserved in their saucers under water, and what colours should be merely covered with oiled paper because the water injures them, he proceeds to communicate "a curious mode of preserving oil-colours," and of transporting them from place to place. The important secret is to tie them in bladders, the mode of doing which he enters into with great minuteness, as if the invention was recent. It is true, Christoforo Sorte, in describing his practice in water-colour drawing, says he was in the habit of preserving a certain vegetable green with gum-water in a bladder; but as the method was obviously new to Palomino, there seems sufficient reason to believe that oil-colours, when once ground, had, up to his time, been kept in saucers and preserved under water.[35] Among the items of expense in the Treviso document before alluded to, we find "a pan and saucers for the painters."[36] This is in accordance with Cennini's directions, and the same system appears to have been followed till after 1700.[37]
The Flemish accounts of the early practice of oil-painting are all later than Vasari. Van Mander, in correcting the Italian historian in his dates, still follows his narrative in other respects verbatim. If Vasari's story is to be accepted as true, it might be inferred that the Flemish secret consisted in an oil varnish like copal.[38] Vasari says, that Van Eyck boiled the oils with other ingredients; that the colours, when mixed with this kind of oil, had a very firm consistence; that the surface of the pictures so executed had a lustre, so that they needed no varnish when done; and that the colours were in no danger from water.[39]
Certain colours, as is well known, if mixed with oil alone, may be washed off after a considerable time. Leonardo da Vinci remarks, that verdigris may be thus removed. Carmine, Palomino observes, may be washed off after six years. It is on this account the Italian writers recommend the use of varnish with certain colours, and it appears the Venetians, and perhaps the Italians generally, employed it solely in such cases. But it is somewhat extraordinary that Vasari should teach a mode of painting in oil so different in its results (inasmuch as the work thus required varnish at last) from the Flemish method which he so much extols—a method which he says the Italians long endeavoured to find out in vain. If they knew it, it is evident, assuming his account to be correct, that they did not practice it.
[1] See "Marcucci Saggio Analitico-chimico sopra i colori," &c. Rome, 1816, and "Taylor's Translation of Merimée on Oil-painting," London, 1839. The last-named work contains much useful information.
[2] Italian writers of the 16th century speak of three kinds. Cardanus says, that of the abies was esteemed most, that of the larix next, and that of the picea least. The resin extracted by incision from the last (the pinus abies Linnæi) is known by the name of Burgundy pitch; when extracted by fire it is black. The three varieties occur in Italian treatises on art, under the names of oglio di abezzo, trementina and pece Greca.
[3] The concrete balsam benzoe, called by the Italians beluzino, and belzoino, is sometimes spoken of as a varnish.
[4] Marcucci supposes that balsam of copaiba was mixed with the pigments by the (later) Venetians.