This writer so frequently alludes to the Flemish painters, of whose great reputation he sometimes seems jealous, that the above strong expression of opinion may have been pointed at them. On the other hand it is to be observed that the term forestieri, strangers, does not necessarily mean transalpine foreigners, but includes those Italians who were not of the Venetian state.[10] The directions given by Raphael Borghini,[11] and after him by Armenini,[12] respecting the use and preparation of varnishes made from the very materials in question, may thus have been comprehended in the censure, especially as some of these recipes were copied and republished in Venice by Bisagno,[13] in 1642—that is, only six years before Boschini's poem appeared.

Ridolfi's Lives of the Venetian Painters[14] (1648) may be mentioned with the two last. His only observation respecting the vehicle is, that Giovanni Bellini, after introducing himself by an artifice into the painting-room of Antonello da Messina, saw that painter dip his brush from time to time in linseed oil. This story, related about two hundred years after the supposed event, is certainly not to be adduced as very striking evidence in any way.[15]

Among the next writers, in order of time prior to Bisagno, may be mentioned Canepario[16] (1619). His work, "De Atramentis" contains a variety of recipes for different purposes: one chapter, De atramentis diversicoloribus, has a more direct reference to painting. His observations under this head are by no means confined to the preparation of transparent colours, but he says little on the subject of varnishes. After describing a mode of preserving white of egg, he says, "Others are accustomed to mix colours in liquid varnish and linseed, or nut-oil; for a liquid and oily varnish binds the (different layers of) colours better together, and thus forms a very fit glazing material."[17] On the subject of oils he observes, that linseed oil was in great request among painters; who, however, were of opinion that nut-oil-excelled it "in giving brilliancy to pictures, in preserving them better, and in rendering the colours more vivid."[18]

Lomazzo (a Milanese) says nothing on the subject of vehicles in his principal work, but in his "Idea del Tempio della Pittura,"[19] he speaks of grinding the colours "in nut-oil, and spike-oil, and other things," the "and" here evidently means or, and by "other things" we are perhaps to understand other oils, poppy oil, drying oils, &c.

The directions of Raphael Borghini and Vasari[20] cannot certainly be considered conclusive as to the practice of the Venetians, but they are very clear on the subject of varnish. These writers may be considered the earliest Italian authorities who have entered much into practical methods. In the few observations on the subject of vehicles in Leonardo da Vinci's treatise, "there is nothing," as M. Merimée observes, "to show that he was in the habit of mixing varnish with his colours." Cennini says but little on the subject of oil-painting; Leon Battista Alberti is theoretical rather than practical, and the published extracts of Lorenzo Ghiberti's MS. chiefly relate to sculpture.

Borghini and Vasari agree in recommending nut-oil in preference to linseed-oil; both recommend adding varnish to the colours in painting on walls in oil, "because the work does not then require to be varnished afterwards," but in the ordinary modes of painting on panel or cloth, the varnish is omitted. Borghini expressly says, that oil alone (senza più) is to be employed; he also recommends a very sparing use of it.

The treatise of Armenini (1587) was published at Ravenna, and he himself was of Faenza, so that his authority, again, cannot be considered decisive as to the Venetian practice. After all, he recommends the addition of "common varnish" only for the ground or preparation, as a consolidating medium, for the glazing colours, and for those dark pigments which are slow in drying. Many of his directions are copied from the writers last named; the recipes for varnishes, in particular, are to be found in Borghini. Christoforo Sorte[21] (1580) briefly alludes to the subject in question. After speaking of the methods of distemper, he observes that the same colours may be used in oil, except that instead of mixing them with size, they are mixed on the palette with nut-oil, or (if slow in drying) with boiled linseed-oil: he does not mention varnish. The Italian writers next in order are earlier than Vasari, and may therefore be considered original, but they are all very concise.

The treatise of Michael Angelo Biondo[22] (1549), remarkable for its historical mistakes, is not without interest in other respects. The list of colours he gives is, in all probability, a catalogue of those in general use in Venice at the period he wrote. With regard to the vehicle, he merely mentions oil and size as the mediums for the two distinct methods of oil-painting and distemper, and does not speak of varnish. The passages in the Dialogue of Doni[23] (1549), which relate to the subject in question, are to the same effect. "In colouring in oil," he observes, "the most brilliant colours (that we see in pictures) are prepared by merely mixing them with the end of a knife on the palette." Speaking of the perishable nature of works in oil-painting as compared with sculpture, he says, that the plaster of Paris (gesso) and mastic, with other ingredients of which the ground is prepared, are liable to decay, &c.; and elsewhere, in comparing painting in general with mosaic, that in the former the colours "must of necessity be mixed with various things, such as oils, gums, white or yolk of egg, and juice of figs, all which tend to impair the beauty of the tints." This catalogue of vehicles is derived from all kinds of painting to enforce the argument, and is by no means to be understood as belonging to one and the same method.

An interesting little work,[24] still in the form of a dialogue (Fabio and Lauro), appeared a year earlier; the author, Paolo Pino, was a Venetian painter. In speaking of the practical methods Fabio observes, as usual, that oil-painting is of all modes of imitation the most perfect, but his reasons for this opinion seem to have a reference to the Venetian practice of going over the work repeatedly. Lauro asks whether it is not possible to paint in oil on the dry wall, as Sebastian del Piombo did. Fabio answers, "the work cannot last, for the solidity of the plaster is impenetrable, and the colours, whether in oil or distemper, cannot pass the surface." This might seem to warrant the inference that absorbent grounds were prepared for oil-painting, but there are proofs enough that resins as well as oil were used with the gesso to make the preparation compact. See Doni, Armenini, &c. This writer, again, does not speak of varnish. These appear to be the chief Venetian and Italian authorities[25] of the sixteenth and part of the following century; and although Boschini wrote latest, he appears to have had his information from good sources, and more than once distinctly quotes Palma Giovane.