a method of painting with water-colours on fresh plaster while it is still in a soft state, by which means the colours are incorporated with the plaster, and become as permanent as the material on which they are spread. The Italians, from whom we borrow the term, call it fresco (literally fresh), either because it is executed upon fresh plaster, or because it is used on walls, alcoves, and other buildings in the open air. Vitruvius (vii. 4) calls it painting udo tectorio.

Painting in fresco is a very ancient art. It was practised by the early Greeks, and may be traced even to Egypt. It is generally executed on walls and vaults, the plaster being laid on in successive portions, or so much only at one time as the painter can despatch before it dries. The design is usually drawn previously on paper, to be chalked and transferred to the wall about half-an-hour after the plaster has been laid. From the difficulty of making alterations on the work when the colours are once absorbed, the design should be previously prepared with the greatest accuracy. When an alteration must be made, the part is usually cut entirely away, and relaid with fresh plaster.

The ancients painted on stucco; and we may remark in Vitruvius what infinite care they took in making the incrustation or plastering of their buildings, to render them beautiful and lasting; though the moderns find a plaster of lime and sand preferable for fresco painting, both because it does not dry so hastily, and on account of its subdued and agreeable tint.

The pigments chiefly employed in this kind of painting are earths, because their colours are not liable to be affected by the burning qualities of the lime. White is made of lime slaked some time previously, or of white marble dust; and the other substances used are red and yellow ochre, verditer, lapis-lazuli, black chalk, &c. These only require to be ground and mixed up with water. The brushes and pencils should be long and soft, otherwise they are apt to rake and raise the surface. In order that the work may come out in all its beauty, the colours must be laid on quickly, while the plaster is still moist; nor should they ever be retouched dry with colours mixed up with the white of egg, size, or gum, as is sometimes done; because such colours grow blackish, and soon tarnish.