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The materials employed by 'picture-makers' are now very numerous. Some of the old pigments, and painting-grounds, and methods, have indeed fallen more or less completely into disuse; but, on the other hand, many new products, both natural and artificial, have been added to the resources of the artist, while several new processes of painting have been introduced, or old methods modified. Nowadays it is very seldom that a painter prepares for himself any one of the materials which he uses, generally accepting, without much hesitation and without examination, the paper, the canvas, the paints, the oils, and the varnishes which his colourman supplies, provided they respond, at first sight, to his requirements. True he has abandoned, not without regret, several of the most treacherous compounds by which his immediate predecessors were seduced. 'Pure scarlet' he has given up; he is shy of asphalt; tobacco-juice and Spanish liquorice are no longer regarded as desirable water-colours. He may go so far as to reject chromate of lead, but he still employs the pigment called chrome green, or green cinnabar, for he does not know that the same chromate of lead enters largely into its composition; and he still thinks that madder yellow is a sound paint, because it is called madder, while he rejects the yellow lakes, which are derived from the same source.
His linseed oil is neither made from pure linseed, nor cold-drawn; his copal varnish may not have a particle of pure copal in it; but both are taken on trust. I do not expect that artists should become chemists trained to test their materials, but they will place themselves in a position of comparative security by acquiring an elementary knowledge of the origin, the composition, and the characteristics of the various products with which their works are constructed. An architect is expected to recognise the sound or unsound quality of the timber, the stone, the brick, the iron, with which the edifice he designs is constructed: why should the painter take everything on trust? The purchaser of a picture ought not to be distressed by doubts as to its stability. The concentration of the artist's attention on the definitely artistic side of his practice must, of course, be in no wise interfered with, but time may still be found for the acquisition of such knowledge of his materials as shall enable him to discriminate between the good and the bad. He may even try, with great advantage, a few simple experiments - experiments performed in a few minutes with the simplest apparatus, and with the most innocent of reagents.
These are the more necessary now that painters no longer buy their raw materials, or make their own paints, and oils, and varnishes, or prepare their own canvases and panels. Before colourmen generally undertook such work, early in the seventeenth century, painters were eager after receipts, and, there can be no doubt, were ignorant of reasons: there was little exact science underlying their art. Yet it would be unfair to the best colourmen of the present day to assume that they do not endeavour to provide, as far as possible, sound materials. But they do not manufacture all they sell. They are not paper-makers, nor, as a rule, are they manufacturers of oils and varnishes. Many of the pigments they furnish are not of their own make. If, for instance, you inquire the source of the artificial ultramarine you purchase of your colourman, you will find that it has probably been made in a factory wholly devoted to the manufacture of that pigment. The production of this material can indeed be properly carried on only in special establishments thoroughly equipped for a peculiar and difficult work. In reality, this specialization ought to be, and generally is, advantageous, but it renders the position of the colourman somewhat difficult.
He has to assume responsibility for the soundness and genuineness of many products of the history and preparation of which he knows little or nothing.
This difficulty confronts him in many directions. I have known cases in which importers or manufacturers' travellers have offered to artists' colourmen speciously prepared but spurious pigments, such as madder carmine and rose madder made from artificial alizarin, ultramarine ash containing not a particle of the native lapis-lazuli, and a gold ochre owing its colour to a basic ferric sulphate instead of a hydrate. Then, too, some of the original localities of a few native earths, such as terre verte and raw umber, are practically exhausted, and most of the new sources yield products of inferior hue. Hence the temptation to 'exalt' the hue of the commercial article by some seductive though dangerous addition.
After these introductory observations, I may refer the reader to the table of contents for the plan of the present book, and to the prefaces for the object with which it has been prepared. I would add, here, only this one remark, that the materials with which a painting is constructed are described in definite order, beginning with the ground, then passing on to the medium and the pigments, not omitting the final varnish, and finally closing with a brief summary of methods of painting, and of the experimental studies by means of which the conclusions given in the earlier portions of the volume have been reached.