PIGMENTS
limit themselves to five colors; and when the palette is extended beyond seven, it is safe to presume that one is skirting the borders either of the amateur or the student class.
So much for pigments. But now we are confronted with another and a still more difficult problem: that of the medium in which the colors are to be mixed. For this purpose nothing better than pure linseed oil has ever been discovered, and indeed nothing better could be desired; for it combines nearly all of the good qualities—transparency, hardness, a certain flexibility when dry, and a durability whose limits we are as yet unable to gauge—the first pictures ever painted in oil colors being still in a good state of preservation. Unfortunately it has now become very difficult to obtain pure linseed oil. Most of the oil of the world is at
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