The art of painting on walls freshly laid with plaster, or which have been damped so as to permit of the colour sinking into the lime; there were two methods, the fresco secco and the fresco buon; in the first the wall was sprinkled with water, and the colours were then worked into the damp surface; in the second process, in which finer and more permanent effects were obtained, the artist worked upon the fresh plaster of the wall (which is laid for him as he proceeds), pouncing or tracing his designs with a stylus; only colours which are natural earths can be employed, as they require to be mixed with lime ere being applied, and are subject to the destroying effect of that substance; as a method of mural decoration it was known to the ancients, and some of the finest specimens are to be seen in the Italian cathedrals of the 14th and 15th centuries; the art is still in vogue, but can only be practised successfully in a dry climate.