Page:The chemistry of paints and painting.djvu/36

 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