There are two kinds of fresco painting - that done when the plaster is wet is called fresco buono; that done after the plaster is dry is called fresco secco. Dampness in the basis is fatal to fresco work. Freestone is a bad basis, and rubble is worse. Brick is perhaps the best, and the brickwork must be perfectly dry before the first coat of plaster is applied. The first coat consists of 2 parts of clean sharp sand, carefully washed to free it from all impurities, mixed with 1 part of best old lime. To prepare the lime, mix it in a trough to the consistency of cream; then pass it through hair sieves into jars, where it must be allowed to settle, the water being poured off. The second coat, or intonaco, is composed of finer materials than are contained in the first coat; the second coat is floated on in two coats, and is properly finished till the surface is true and of an even grain. If the picture is a large one, only as much of the wall's surface as can be covered in a day's work is prepared. While the surface of the wall is still wet, but firm, a cartoon or tracing of the proposed design is laid over the prepared portion of the wall, and the lines of the picture are lightly indented on the wall with a blunt bone or hardwood point.

When the intonaco is firm enough to bear the pressure of the finger, the colour is put on. To hide the joinings between each day s work, the painting is as far as possible suspended at the folds of drapery or in the shadows. The painting must be done quickly, and mistakes can only be rectified by cutting out the defective piece and applying fresh plaster. The colours for fresco work are ground and mixed with water, but only those colours capable of withstanding the action of lime must be used. The following are a few of the suitable colours: Vermilion, Venetian red, Indian red, burnt sienna, aureolin, yellow ochre, terre verte, French blue, ultramarine, cobalt, burnt umber, Verona brown, Vandyke brown, Caledonian brown, raw umber, raw sienna, ivory black, lampblack. It must not be forgotten that the colours dry much lighter than they appear when freshly laid on the wall; the art of mixing the colours, therefore, so as to obtain the desired tone in the finished work can be acquired only by experience. In executing fresco secco the wall is damped before the colours are laid on.

It is, of course, a less tedious and less troublesome process than fresco buono, but the result is considered to be inferior.