Farther on, this remark is thus followed out:—
"The paleness or freshness of the tempera may have been sometimes calculated for this brown glazing (for such it was in effect), and when this was the case, the picture was, strictly speaking, unfinished without its varnish. It is, therefore, quite conceivable that a painter, averse to mere mechanical operations, would, in his final process, still have an eye to the harmony of his work, and, seeing that the tint of his varnish was more or less adapted to display the hues over which it was spread, would vary that tint, so as to heighten the effect of the picture. The practice of tingeing varnishes was not even new, as the example given by Cardanus proves. The next step to this would be to treat the tempera picture still more as a preparation, and to calculate still further on the varnish, by modifying and adapting its color to a greater extent. A work so completed must have nearly approached the appearance of an oil picture. This was perhaps the moment when the new method opened itself to the mind of Hubert Van Eyck.... The next change necessarily consisted in using opaque as well as transparent colors; the former being applied over the light, the latter over the darker, portions of the picture; while the work in tempera was now reduced to a light chiaroscuro preparation.... It was now that the hue of the original varnish became an objection; for, as a medium, it required to be itself colorless."—Ib. pp. 271-273.
119. Our author has perhaps somewhat embarrassed this part of the argument, by giving too much importance to the conjectural adaptation of the tints of the tempera picture to the brown varnish, and too little to the bold transition from transparent to opaque color on the lights. Up to this time, we must remember, the entire drawing of the flesh had been in tempera; the varnish, however richly tinted, however delicately adjusted to the tints beneath, was still broadly applied over the whole surface, the design being seen through the transparent glaze. But the mixture of opaque color at once implies that portions of the design itself were executed with the varnish for a vehicle, and therefore that the varnish had been entirely changed both in color and consistence. If, as above stated, the improvement in the varnish had been made only after it had been mixed with opaque color, it does not appear why the idea of so mixing it should have presented itself to Van Eyck more than to any other painter of the day, and Vasari's story of the split panel becomes nugatory. But we apprehend, from a previous passage ([p. 258]), that Mr. Eastlake would not have us so interpret him. We rather suppose that we are expressing his real opinion in stating our own, that Van Eyck, seeking for a varnish which would dry in the shade, first perfected the methods of dissolving amber or copal in oil, then sought for and added a good dryer, and thus obtained a varnish which, having been subjected to no long process of boiling, was nearly colorless; that in using this new varnish over tempera works he might cautiously and gradually mix it with the opaque color, whose purity he now found unaffected, by the transparent vehicle; and, finally, as the thickness of the varnish in its less perfect state was an obstacle to precision of execution, increase the proportion of its oil to the amber, or add a diluent, as occasion required.
120. Such, at all events, in the sum, whatever might be the order or occasion of discovery, were Van Eyck's improvements in the vehicle of color, and to these, applied by singular ingenuity and affection to the imitation of nature, with a fidelity hitherto unattempted, Mr. Eastlake attributes the influence which his works obtained over his contemporaries:—
"If we ask in what the chief novelty of his practice consisted, we shall at once recognize it in an amount of general excellence before unknown. At all times, from Van Eyck's day to the present, whenever nature has been surprisingly well imitated in pictures, the first and last question with the ignorant has been—What materials did the artist use? The superior mechanical secret is always supposed to be in the hands of the greatest genius; and an early example of sudden perfection in art, like the fame of the heroes of antiquity, was likely to monopolize and represent the claims of many."—Ib. p. 266.
This is all true; that Van Eyck saw nature more truly than his predecessors is certain; but it is disputable whether this rendering of nature recommended his works to the imitation of the Italians. On the contrary, Mr. Eastlake himself observes in another place (p. 220), that the character of delicate imitation common to the Flemish pictures militated against the acceptance of their method:—