In the older times, when rare and valuable pigments were used, as well as large quantities of pure gold, the materials to be employed and their value were stipulated for in the contract made between the painter and his employer before the picture was begun, and an artist's remuneration at that time was much of the nature of a salary, calculated on an approximate guess at the time he might need for the work. That was, of course, a survival from the time of the Byzantine artists, to whom gold and silver and paints were weighed out by the ecclesiastics for whom they painted, and had to be accounted for in the finished picture. There is a story told of an artist's apprentice, who made a considerable sum of money by selling the washings of his master's brushes when the latter was using a great quantity of ultramarine; and that shows the costliness of mere paints at that time. As for the more valuable materials, the great altar picture in Saint Mark's, in Venice, is entirely composed of plates of pure gold enamelled in different colours, and fastened in a sort of mosaic upon the wood panel as required, the lights and shades being produced by hatching regular lines through the hard enamel with a sharp instrument. The whole technical history of painting lies between that sort of work and the modern painter's studio. Before oil painting became general, artists were largely dependent on commissions in order to do any work except drawing. Fresco needed a wall, and work done in that manner could not be removed from place to place. The old-fashioned panel work with its gold background was so expensive that few artists could afford to paint pictures on the mere chance of selling them. But the facilities and the economy of pure tempera work, and work in oils, soon made easel pictures common. Between the time of Giotto and that of Mantegna another means of expression, besides painting, was found for artists, if not by accident, by the ingenuity of the celebrated goldsmith, Maso Finiguerra, who was the first man in Italy, and probably the first in the world, to take off upon paper impressions in ink from an engraved plate. [Illustration: THE PALATINE]