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]