112. On the white surface thus prepared, the colors, ground finely with linseed oil, were applied, according to the advice of Theophilus, in not less than three successive coats, and finally protected with amber or sandarac varnish: each coat of color being carefully dried by the aid of heat or in the sun before a second was applied, and the entire work before varnishing. The practice of carefully drying each coat was continued in the best periods of art, but the necessity of exposure to the sun intimated by Theophilus appears to have arisen only from his careless preparation of the linseed oil, and ignorance of a proper drying medium. Consequent on this necessity is the restriction in Theophilus, St. Audemar, and in the British Museum MS., of oil-painting to wooden surfaces, because movable panels could be dried in the sun; while, for walls, the colors are to be mixed with water, wine, gum, or the usual tempera vehicles, egg and fig-tree juice; white lead and verdigris, themselves dryers, being the only pigments which could be mixed with oil for walls. But the MS. of Eraclius and the records of our English cathedrals imply no such absolute restriction. They mention the employment of oil for the painting or varnishing of columns and interior walls, and in quantity very remarkable. Among the entries relating to St. Stephen's chapel, occur—"For 19 flagons of painter's oil, at 3s. 4d. the flagon, 43s. 4d." (It might be as well, in the next edition, to correct the copyist's reverse of the position of the X and L, lest it should be thought that the principles of the science of arithmetic have been progressive, as well as those of art.) And presently afterwards, in May of the same year, "to John de Hennay, for seventy flagons and a half of painter's oil for the painting of the same chapel, at 20d. the flagon, 117s. 6d." The expression "painter's oil" seems to imply more careful preparation than that directed by Theophilus, probably purification from its mucilage in the sun; but artificial heat was certainly employed to assist the drying, and after reading of flagons supplied by the score, we can hardly be surprised at finding charcoal furnished by the cartload—see an entry relating to the Painted Chamber. In one MS. of Eraclius, however, a distinct description of a drying oil in the modern sense, occurs, white lead and lime being added, and the oil thickened by exposure to the sun, as was the universal practice in Italy.
113. Such was the system of oil-painting known before the time of Van Eyck; but it remains a question in what kind of works and with what degree of refinement this system had been applied. The passages in Eraclius refer only to ornamental work, imitations of marble, etc.; and although, in the records of Ely cathedral, the words "pro ymaginibus super columnas depingendis" may perhaps be understood as referring to paintings of figures, the applications of oil, which are distinctly determinable from these and other English documents, are merely decorative; and "the large supplies of it which appear in the Westminster and Ely records indicate the coarseness of the operations for which it was required." Theophilus, indeed, mentions tints for faces—mixturas vultuum; but it is to be remarked that Theophilus painted with a liquid oil, the drying of which in the sun he expressly says "in ymaginibus et aliis picturis diuturnum et tædiosum nimis est." The oil generally employed was thickened to the consistence of a varnish. Cennini recommends that it be kept in the sun until reduced one half; and in the Paris copy of Eraclius we are told that "the longer the oil remains in the sun the better it will be." Such a vehicle entirely precluded delicacy of execution.
"Paintings entirely executed with the thickened vehicle, at a time when art was in the very lowest state, and when its votaries were ill qualified to contend with unnecessary difficulties, must have been of the commonest description. Armorial bearings, patterns, and similar works of mechanical decoration, were perhaps as much as could be attempted.
"Notwithstanding the general reference to flesh-painting, 'e così fa dello incarnare,' in Cennini's directions, there are no certain examples of pictures of the fourteenth century, in which the flesh is executed in oil colors. This leads us to inquire what were the ordinary applications of oil-painting in Italy at that time. It appears that the method, when adopted at all, was considered to belong to the complemental and merely decorative parts of a picture. It was employed in portions of the work only, on draperies, and over gilding and foils. Cennini describes such operations as follows. 'Gild the surface to be occupied by the drapery; draw on it what ornaments or patterns you please; glaze the unornamented intervals with verdigris ground in oil, shading some folds twice. Then, when this is dry, glaze the same color over the whole drapery, both ornaments and plain portions.'
"These operations, together with the gilt field round the figures, the stucco decorations, and the carved framework, tabernacle, or ornamento itself of the picture, were completed first; the faces and hands, which in Italian pictures of the fourteenth century were always in tempera, were added afterwards, or at all events after the draperies and background were finished. Cennini teaches the practice of all but the carving. In later times the work was divided, and the decorator or gilder was sometimes a more important person than the painter. Thus some works of an inferior Florentine artist were ornamented with stuccoes, carving, and gilding, by the celebrated Donatello, who, in his youth, practiced this art in connection with sculpture. Vasari observed the following inscription under a picture:—'Simone Cini, a Florentine, wrought the carved work; Gabriello Saracini executed the gilding; and Spinello di Luca, of Arezzo, painted the picture, in the year 1385.'"—Ib. pp. 71, 72, and 80.
114. We may pause to consider for a moment what effect upon the mental habits of these earlier schools might result from this separate and previous completion of minor details. It is to be remembered that the painter's object in the backgrounds of works of this period (universally, or nearly so, of religious subject) was not the deceptive representation of a natural scene, but the adornment and setting forth of the central figures with precious work—the conversion of the picture, as far as might be, into a gem, flushed with color and alive with light. The processes necessary for this purpose were altogether mechanical; and those of stamping and burnishing the gold, and of enameling, were necessarily performed before any delicate tempera-work could be executed. Absolute decision of design was therefore necessary throughout; hard linear separations were unavoidable between the oil-color and the tempera, or between each and the gold or enamel. General harmony of effect, aërial perspective, or deceptive chiaroscuro, became totally impossible; and the dignity of the picture depended exclusively on the lines of its design, the purity of its ornaments, and the beauty of expression which could be attained in those portions (the faces and hands) which, set off and framed by this splendor of decoration, became the cynosure of eyes. The painter's entire energy was given to these portions; and we can hardly imagine any discipline more calculated to insure a grand and thoughtful school of art than the necessity of discriminated character and varied expression imposed by this peculiarly separate and prominent treatment of the features. The exquisite drawing of the hand also, at least in outline, remained for this reason even to late periods one of the crowning excellences of the religious schools. It might be worthy the consideration of our present painters whether some disadvantage may not result from the exactly opposite treatment now frequently adopted, the finishing of the head before the addition of its accessories. A flimsy and indolent background is almost a necessary consequence, and probably also a false flesh-color, irrecoverable by any after-opposition.
115. The reader is in possession of most of the conclusions relating to the practice of oil-painting up to about the year 1406.