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Rh with the discovery of many things in the properties of colours, which he had learned from ancient traditions recorded by Pliny and other writers." P'ilarete (c. 1464) also knew of the repute of Jan van Eyck in connexion with the oil technique. Hence we may credit the Van Eycks with certain technical improvements on traditional practices and preparations in the oil technique, though these can hardly be termed " inventions, " while their artistic achievement was great enough to force into prominence whatever in the technical department they had accomplished.

Another and a more important question remains behind: What was, in fact, the practice in the matter of oil painting in vogue before the Van Eycks, altered or at any rate perfected by them and their successors, and in general use up to the time of Vasari; and how was it related to the older more widely diffused painting " a tempera "?

It is indisputable that the oil painting of the Van Eycks and the early Flemish school, together with that of the Florentines and Umbrians, and indeed of all the Italians up to Vasari's time, save the Venetians, Correggio, and some other north Italians, does not greatly differ in artistic effect, nor, as far as can be judged, in handling, from earlier or contemporary temperas. For example, at Venice in the 15th century, Crivelli paints always in tempera, Cima in oils, but the character of their surface is almost the same, and if anything the tempera is richer in effect than the oil. The contrary is no doubt the case with the tempera " Madonna with the Violet " in the Priests' Seminary at Cologne when compared with the somewhat later " Dombild, " also by Stephan Lochner, which is believed to be painted in oils, but the two are still in technical character very nearly akin. The fact is that tempera panels were usually coated with an oil varnish, necessarily of a somewhat warm tint, and we could hardly expect to distinguish them from oil pictures painted in or covered by varnish, unless there were a difference in the handling of the pigments. The method of handling appears however to be on the whole the same, and there are many who believe that in all essentials it is the same. Tempera panels, as we have learned from Cennino, were not only varnished but in parts might be painted in oils (ch. 143), and it is one view of the technique of the early Flemings that it was only an over-painting in oils over a preparation in tempera. Berger is of the opinion that the process was something between the two, that is to say, that it was oil tempera, the medium being an emulsion of oil and water through the intermediary of a gum. Such a medium would, as he points out {Beitrdgc, III. 247 seq.), combine the thinness and limpidity in manipulation characteristic of a water tempera with the property of drying hard and impervious to moisture. This is of course only a theory. Of far more weight is the suggestion made by Principal Laurie, of Edinburgh, who has carried on for years a series of careful experiments in the various pigments and media employed in oil painting. As one result of these experiments he has found that the ordinary drying oils and oil varnishes do not, as used to be assumed, " lock up " or completely cover and protect pigments so as to prevent the access of moisture and the gases of the atmosphere, but that this function is far more effectively performed by hard pine-balsams, such as Canada balsam, dissolved in an essential oil and so made into a varnish or painting medium. In pictures by Van Eyck Principal Laurie has detected what he believes to be the use of pigments of a notoriously fugitive character, and he is convinced that the most effectual medium for preserving these in the condition in which they have come down to us would be a natural pine-balsam, with probably a small proportion of drying oil; he suggests therefore that the introduction of these ingredients may be the real secret of the Van Eyck technique. There is as yet no proof that the Van Eycks really used such a medium, though it is a preparation possible at their time, and when thinned by a process of emulsification with egg, as Dr Laurie suggests, would be a serviceable one; but they and the other early oil painters certainly used a method, and in all probability media, that did not differ greatly as regards manipulation from those in vogue in tempera.

From the aesthetic point of view therefore we have to regard early oil painting as only another form of the older tempera,

expressing exactly the same artistic ideals and dominated by the same view of the relation of art to nature. To Vasari the artistic advantage of the oil medium was, first, its convenience, and, next, the depth and brilliancy it lent to the colours, which he says it

" kindled, " while at the same time it lent itself to a soft fusing of tints in manipulation, so that artists could give to their figures in this technique the greatest charm and beauty combined with a force that made them seem to stand out in relief from the paneL Such a description applies very justly to work like that of the Van Eycks in the " Adoration of the Lamb, " or the later panels of Anlonello da Messina, who, according to Vasari's often repeated story, introduced the Flemish system of oil-painting into Venice. The description does not however apply to the freer, more sweeping, more passionate handling of the brush by the greatest of the Venetians such as Titian or 'eronese, and still less to the oil painting of 17th-century masters like Rubens or Rembrandt or Velazquez. It is quite clear that whatever improvements in oil technique were due to the early Flemings, oil painting in the modern sense owes still more to the Venetians, who first taught the world the full artistic possibilities of the process. Giovanni Bellini, whose noble altarpiece in S. Pietro at Murano may be called, in a phrase once applied to another of his pictures, " the canon of V'enetian art, " is probably entitled to be called the father of modern oil painting. Beginning as a painter in tempera and adopting the new process about 1475, Bellini was able so far to master the new medium that he handed it on with all its possibilities indicated to Giorgione, Palma and Titian. That Venetian oil painting however, with all its briDiancy and freedom, was a child of the older tempera technique is shown by its characteristic method, which consisted in an under-painting in dead colour, over which were superimposed the transparent glazes that secured the characteristic Venetian richness of colouring. Now all the recent writers on the Van Eyck technique agree that, whatever were the exact media employed, the tempera tradition, and perhaps the tempera vehicles, were maintained for the under painting. In the old tempera-panel technique of Cennino there was a monochrome under painting in a greenish pigment, over which the flesh tints were spread in thin layers so as never completely to obliterate the ground. Such an under painting in a few simple colours, black, white and red, was employed by Titian and others of the Venetians, and over it were laid the rich juicy transparent pigments, till " little by little he would have covered with real living flesh these first abstracts of his intention " (Boschini). There is some evidence that in many cases these under paintings were in tempera, which would have the advantage of drying more quickly than under paintings in oil, and Boschini {Le Ricchc minerc ddla piitura veneziana, 1674) e.xpressly says that the blues in Venetian paintings, e.g. by Veronese, were painted often a guazzo. There was a reason, however, why the Venetians would alter the traditional practice of the Flemish forerunners. The latter were almost entirely panel painters, while the Venetians used canvas. Now certain media, like the hard pine-balsams which Dr Laurie thinks were the basis of the Van Eyck medium, are suitable for the immovable surfaces of a well-grounded panel, but would be liable to crack on canvas which is more or less yielding. Hence the tougher oil vehicles were in advanced 'enetian painting exclusively employed.

This distinction between the thin transparent pigments and those of an opaque body, which is as old as oil painting in any form, becomes in the hands of Bellini and the later ^'enetians the fundamental principle of the technique. The full advantage of this thinness and transparency is gained by the use of the pigments in question as " glazes " over a previously laid solid impasto. This impasto may be modelled up in monochrome or in any desired tints chosen to work in with the colours of the superimposed glazes. Effects of colour of great depth and brilliancy may thus be obtained, and after the glaze has been floated over the surface a touch of the thumb, where the under painting is loaded and lights are required, will so far thin it as to let the underlying colour show through and blend with the deeper tint of the glaze in the shadows. Thus in the noble Veronese in