STUCCO. A name sometimes, though incorrectly, applied to all descriptions of lime or cement renderings on masonry, whether external or internal, but which is really given by builders to a species of plastering, in ordinary cases worked up by hand to a fine face adapted to receive paint ; or in superior buildings made by the addition of other materials than the limo, or plaster, usually employed, in order to resemble marble. Common stucco, in fact, is nothing more than plastering which has received an additional amount of manipulation ; marble stucco is made with fine lime (composed of the pure hydrate of that base) mixed with ealceroous powder, chalk, or other analogous substances in such proportions and worked in such manner as to pro duce a hard, uniform surface, which admits of being coloured, painted, and polished so as to represent valuable marbles. It is employed in decorative architecture to cover columns, pilasters, walls, cornices, plinths, &c., in sheltered or covered positions : in external works, the natural or the artificial calcareous cements, or the oleaginous cements, are employed for this purpose—a distinction unknown by the Italians who first used the " stucco tura," from whence we have derived the art, and the name, of the fine plastering used by us exclusively for decorative and internal works.
Uniform marble stucco is prepared by mixing pounded white Carrara marble, or gypsum in the form of the white alabaster, with rich lime carefully slaked and run through a sieve, and the mixture is trowelled on to a rough rendering coat until the surface is perfectly even and homogeneous. Different colours are communicated by the addition of the metallic oxides, and when very delicate tints are required plaster mixed or gauged with water containing size, fish-glue, or gum arabic, is substituted for the hydrate of lime. The polishing is only commenced when the surface is perfectly dry, and it is effected by the use of fine grits, tripoli powder, chalk, and oil; very much in the same manner that marble is polished. Scagliola is executed with the same class of materials as the marble stuccos ; but small splinters (or ocagliolc) of the marble desired to be imitated, should the latter present much variety of effect, are introduced in the finishing coats. Of late years the Keene's and the Parian cements have been exclusively used in London, instead of the ancient marble stuccos.