Titian's stay in Rome was short, and with respect to the Treviso altar-piece, a week or two only, at most, can have elapsed between the completion and the varnishing. Cennini, who recommends delaying a year at least before varnishing, speaks of pictures in distemper.

See Borghini, Armenini, their Venetian copyist Bisagno, and Palomino. The last-named writer, though of another school and much more modern, was evidently well acquainted with the ancient methods: he says, "Se advierte que siempre que se huviere de barnizar alguna cosa conviene que la pintura y el barniz estèn calientes."—El Museo Pictorico, v. ii.

Burnt alum, one of the ingredients recommended, might perhaps account for a shining fracture in the indurated pigment in some old pictures.

Of the earlier Spanish writers Pacheco may be mentioned next to Palomino as containing most practical information. Carducho, De Butron, and others, seldom descend to such details. Palomino contains all the directions of Pacheco, and many in addition.

See Cean Bermudez, "Sobre la Escuela Sevillana," Cadiz, 1806. The same reasons induced the later Venetian machinists to paint on dark grounds, and to make use of (drying) oil in excess. See Zanetti, Della Pittura Veneziana, 1. iv.