[29] Federici, "Memorie Trevigiane," Venezia, 1803. The altar-piece of S. Niccolo at Treviso is attributed, in the document alluded to, to Fra Marco Pensabene, a name unknown; the painting is so excellent as to have been thought worthy of Sebastian del Piombo: for this opinion, however, there are no historical grounds. It was begun in 1520, but before it was quite finished the painter, whoever he was, absconded: it was therefore completed by another. [30] 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. [31] 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. [32] Burnt alum, one of the ingredients recommended, might perhaps account for a shining fracture in the indurated pigment in some old pictures. [33] 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. [34] 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. [35] Borghini, in describing the method of making a gold-size (the same as Cennini's), speaks of boiling the "buccie de' colori" in oil; this only means the skin or pellicle of the colour itself--in fact, he proceeds to say that they dissolve in boiling. Vasari, in describing the same process, uses the expression "colori seccaticci." [36] "Maggio 4 (1520) Per un cadin (catino) per depentori. Per scudellini per li depentori."--_Mem. Trev._, vol. i. p. 131. Pungileoni ("Memorie Istoriche di Antonio Allegri") quotes a note of expenses relating to two oil-pictures by Paolo Gianotti; among the items we find "colori, telari, et brocchette."--vol. ii. p. 75. [37] Salmon, in his "Polygraphice" (1701), gives the following direction:--"Oyl colors, if not presently used, will have a skin grow over them, to prevent which put them into a glass, and put the glass three or four inches under water," &c. [38] This varnish appears to have been known some centuries before Van Eyck's time, but he may have been the first to mix it with the colours. [39] See Vasari, Life of Antonello da Messina. NOTE W.--Par. 608.