Luca was an enterprising artist, and it occurred to him that if he could only dispense with the chiselling and casting, his art and profit would both improve. But how could he make the clay as hard as bronze and as white as marble? Remember that Luca was a sculptor, not a potter. Whatever he did afterward, there can be no doubt that his attention was first turned to statuary. He probably decided upon applying to the men who were accustomed to working in clay, to coloring it and glazing it, to help him in his difficulty. He inquired, and learned that by dipping his statuary in tin enamel and firing it, his object would be accomplished. These considerations give his supposed discovery a new aspect. If we consider that for centuries stanniferous enamel had been in use by Eastern potters, and that the Saracens were perfectly familiar with it, the secret is divested of all mystery. Luca probably acquired his knowledge in one or other of the Italian potteries. What, then, are we to credit to him? He must be admitted to have improved the enamel after a series of experiments, and to have succeeded in bringing it to the degree of fineness and opacity demanded by his purpose (Fig. 204). His first work was a bas-relief of the Resurrection, made about the year 1440, and still standing in the Cathedral of Florence. This piece is of blue and white, the latter for the figures, the former for the ground. He afterward introduced green and yellow, but these colors are very sparingly used. His best works are in and around Florence. Of a Madonna in the circle above a chapel door, Ruskin, in his “Mornings in Florence,” says: “Never pass near the market without looking at it; and glance from the vegetables underneath to Luca’s leaves and lilies, that you may see how honestly he was trying to make his clay like the garden stuff.” The same colors are introduced in a bas-relief in the Castellani collection, in which the Madonna kneels before the Infant Saviour, and angels look down from above. The figures are white, the ground blue, and green is introduced in the grass. Of the same class is the preceding example (Fig. 205) from Boston. [Illustration: Fig. 206.--Medallion by Luca della Robbia. (South Kensington Museum.)] [Illustration: Fig. 207.--Andrea della Robbia. Holy Family. (Boston Mus. of Fine Arts.)]