138 2. Oils and Varnishes. The introduction of oil paint ing on the modern methods dates from the time of John Van Eyck. This artist introduced a varnish, probably composed of linseed or nut oil mixed with some resinous substance, which was more siccative than the oil vehicles previously in use, and possessed the property of drying without exposure to the sun or to artificial heat. The oil painting of the early Flemish masters was, strictly speaking, (oil) varnish painting : an oleo-resinous substance, such as amber varnish, was mixed with the colours, and rendered final varnishing unnecessary. The Venetian painters also adopted this vehicle. The term " vehicle " is borrowed from pharmacy. In art it is applied to the fluid used for bringing the pigments into a proper working state. Painters differ greatly as to the vehicles they employ : some use oil only ; others peculiar compounds of their own, made of linseed, poppy, or walnut oils, copal or amber varnishes, drying oil and mastic, &c. Siccatif, a medium specially prepared for oil painting, is now largely used ; mixed with spirits of wine, it forms a beautiful transparent varnish. 3. Colours. The permanent colours are the earths and ochres and those mineral colours which bear the test of fire and lime. Colours prepared from lead and animal and vegetable substances are more or less fugitive. Artist s colours were originally kept in a dry state, and afterwards in small bladders ; they are now enclosed in very con venient collapsable metal tubes. The discoveries of modern chemistry have added largely to the simple list of colours known to the old masters, but perhaps with little advantage to their successors, for their is much truth in the maxim that " the shortest way to good colouring is through a simple palette. " Pliny asserts that the ancient Greek painters employed but four colours in their works. A large proportion of colours, such as the ochres, ver milion, ultramarine, <fcc., is derived from minerals; indigo, madder, gamboge, &c., from vegetable, and carmine, Indian yellow, sepia, &c., from animal substances. The j artificial or chemical preparations include Prussian blue, j Naples yellow, zinc white, French blue, cobalt, the lakes, &c. The natural or true pigments are prepared for use by calcining and washing, and for oil painting are ground up in poppy or linseed oils. With two or three exceptions the pigments derived from the mineral kingdom are .the most permanent, especially those containing iron or copper. Those derived from animal and vegetable substances have less permanence, but they form an important acquisition to the palette, as they not unfrequently possess a purity and brilliancy of colour which makes it almost impossible to dispense with them. Colours are opaque or transparent. The former, on account of their solidity and opacity, are employed to represent light. For shadows and glazing transparent pigments are used. Yellow, red, and blue cannot be com posed, and are called primary colours. The union of two of these in the three combinations of which alone they admit produces secondary colours. White represents light, and in oil painting the only white pigment used is white lead, prepared with great care. The ochres are the most permanent yellows. Their composition is very vari able, but they may be considered true chemical combinations of clay and oxide of iron. The native ochres are yellow and red. By calcination the yellow ochres become red. Other yellows are prepared from arsenic, lead, and vegetable substances. Iron is the great colouring principle of red in nature. All the three kingdoms mineral, animal, and vegetable contribute to the red pigments. The first supplies vermilion and the red ochres ; the second carmine, obtained from the cochineal insect ; the third the madder pigments. The principal blue pigments are ultramarine (native and artificial), cobalt, smalt, Prussian blue, and indigo. Ultramarine is the only pure primary colour ; the finer specimens have neither a tinge of green on the one hand nor of purple on the other. It is obtained from the mineral lazulite or lapis-lazuli, and is probably a volcanic product, as it resists the action of fire. Its scarcity, and consequent high price, have produced many artificial imitations. These are of many qualities. The inferior are used in paper staining, the finer alone being reserved for artists use. Cobalt is now prepared in a state of great purity, but it has the objection of appearing violet in artificial light. In " guides to oil painting " long lists of pigments are generally given ; but these serve only to perplex and embarrass. About a dozen colours, judiciously chosen, will be quite sufficient to supply the palette. Processes and Manipulations. There are various tech nical distinctions in the modes of applying the colours to a picture in its successive stages. Glazing is the laying of thinly transparent colours, diluted with a considerable quantity of vehicle, which allows the work beneath to appear distinctly through, but tinged with the colour of the glaze. The Venetian painters, Titian especially, largely employed this process, advancing their pictures as far as possible with solid, opaque colour, and upon this ground glazing repeatedly the richest and purest colours. The process of glazing is generally effected by the applica tion of diluted transparent colour, but semi-transparent colours are also used when rendered sufficiently trans parent by the admixture of a large proportion of vehicle. When carried to excess, the result is a " horny " impure dulness of surface and a heavy and dirty tone of colour. Much practice and experience are required for its proper performance. Scumbling resembles glazing in that a very thin coat is spread lightly over portions of the work, but the colour used is opaque instead of transparent. A hog- hair brush sparingly charged with the tint is employed. Carried to excess, scumbling produces a " smoky " appear ance. Impasting is the term applied to laying colours in thick masses on the lights. The shadows or dark portions of a picture are painted thinly and transparently, the lights solidly, with opaque colours. Impasting gives " texture " and " surface " to the latter, and helps to produce the appearance of roundness and relief. When carried too far it produces an appearance of coarseness and affords a lodgment for dirt and varnish in what should be the brightest and purest passages in the colouring. Irregularities of surface in such passages of a picture as it may be desirable to repaint are removed by using an instrument especially made for the purpose ; but an old razor, an ordinary pocket-knife, or a piece of window glass, properly broken, will, in skilful hands, answer the purpose equally well. This process should not be attempted till the colour to be removed has hardened, otherwise the pigment will tear off and leave the surface in a condition which it will be found difficult to remedy. It is the practice of some artists to lay the colours at first cold and pale, gradually strengthening the light and shade, and enforcing the colour in subsequent paintings. When this practice is adopted, the colours used should be as few and as simple as possible. It sometimes happens that considerable portions of the first painting are apparent through all the subsequent processes, and this early part of the work should be done with great care and judgment. The first principle in the application of paint is to avoid unnecessary mixing, or, as it is called, " troubling " or saddening the tints, the result of which is a waxy surface and muddiness of colour. When this is avoided the touches are clear and distinct, but when the principle is carried to
