a method of painting in relievo on walls, so as to endure the weather. It is performed with water-colours on fresh plaster, or on a wall laid with mortar not yet dry. This sort of painting has a great advantage by its incorporating with the mortar, and drying along with it, becomes very durable. The Italians, from whom we borrow the term, call it fresco; because it is frequently used for walls, alcoves, and other buildings in the open air. Vitruvius, lib. vii. cap. 4. calls it udo teitorio.

Painting in fresco is very ancient, having been practised in the earliest ages of Greece and Rome. It is chiefly performed on walls and vaults, newly plastered with lime and sand; but the plaster is only to be laid, in proportion as the painting goes on; no more being to be done at once than the painter can dispatch in a day, while it dries. Before he begins to paint, a cartoon or design is usually made on paper, to be called, and transferred to the wall, about half an hour after the plaster is applied.

The ancients painted on stucco; and we may remark in Vitruvius what infinite care they took in making the incrustation or plattering of their buildings to render them beautiful and lasting; though the modern painters find a plaster made of lime and sand preferable to it; both as it does not dry so hastily, and as being a little brownish, it is fitter to lay colours on, than a ground so white as stucco.

In this kind of painting, all the compound and artificial colours, and almost all the minerals, are set aside, and scarce any thing is used but earths; which are capable of preserving their colour, defending it from the burning of the lime, and resisting its salt, which Vitruvius calls its bitterness.

For the work to come out in all its beauty, the colours must be laid on quick; while the plaster is yet moist; nor should they ever be retouched, dry, with colours mixed up with the white of an egg, or size, or gum, as some workmen do; because such colours grow blackish; nor do any preserve themselves, but only such as were laid on hastily at first.

The colours used are white made of lime flaked long before, and white marble dust; ochre, both red and yellow; verditer; lapis lazuli; smalt; black chalk, &c. All which are only ground, and worked up with water; and most of them grow brighter and brighter as the fresco dries.

The brushes and pencils for this work ought to be long and soft, otherwise they will rake and raise the painting. The colours should be full, and flowing from the brush; and the design perfect; for in this work you cannot alter or add upon any colour.

FRESH-WATER, is that not tinctured or impregnated with salt or saline particles, enough to be discoverable by the sense. Such generally is that of springs, rains, wells, lakes, &c.

The dulcifying or making of salt water fresh is a secret that has been long fought with great attention. For an account of the principal attempts that have been made with this view, see Sea-Water.