SCAGLIOLA (from the Italian scaglia, a scale or shell) is an in crustation of artificial composition which is applied to columns, and produces the most perfect imitation of marble, from which it can hardly be distinguished either by the eye or the touch, as it takes an equally high polish and feels equally hard and cold. Scagliola has long been in use in Italy, where, according to Lanzi, it was invented by Guido Fared of Carpi (1584-1649), and where it was afterwards much used for Florentine or inlay-work of the kind called a cOmintsso. It was not introduced into this country before the latter half of the last century, and the earliest application of it was in the columns of the Pantheon in Oxford-street, London, built by James Wyatt. Since that time, it has been brought into more general use, the manufacture of it has been considerably improved, and it can be executed at a com paratively moderate cost. In fact, it haft to a great extent superseded the use of coloured marbles for columns and other interior decorations. .1t is far lees costly than any kind of variegated marble, though too expensive to be brought into ordinary use on every occasion, and it answers the purpose of the real material not only as regards appearance and effect, but durability also, since it will last quite as long as any other part of the interior of a building. There is besides the advan tage attending it ;that columns incrusted with scagliola may be made of wood and hollow, or else filled with a plaster core, and consequently do not require that support in the -floor beneath them, which would be necessary if solid marble shafts were employed ; or if required to support a bearing above them, the columns maybe of brick or ordinary stone, and afterwards coated with acagliola. Nor is the use of this composition confined to columns and pilasters only, for it may be and indeed is applied to other ornamental purposes, for table-slabs, pedestal stands, daubs of rooms, borders of floors, &c.
The composition or cement itself is prepared from the purest gypsum, which is first broken into small pieces, and after being calcined is reduced to powder. It is then passed through a fine sieve, and mixed with Flanders glue, isinglass, &c. In this state it is mixed up with colouring matter of the line required ; and as it is generally em ployed for the imitation of variegated or veined marbles (all coloured ones being more or less so), as many different colours and shades of the same colour must be mixed up separately as there are in the kind of marble to be imitated. Thus prepared, the composition is applied to column+, or other surface intended to receive it, and which has a rough coating of lime and hair. The different colours are laid on and mixed by the workman, and consequently much depends upon his skill and taste in regard to the exactness of the imitation or the beauty of the veining and streaking, which is done in the floating, as it is termed, or laying on the cement. The next operation is to prepare the surface for polishing, by rubbing it with pumice-stone and cleansing it with a wet sponge. The polish is then given by rubbing it again, first with tripoli and charcoal on a piece of fine linen, secondly with felt dipped in tripoli and oil,and lastly with oil alone. By this means a durable lustre Is obtained equal to that of the finest and most highly polished marble. By means of acagliola, not only may tho costliest and rarest atones, porphyry, verde entice, giallo antico, &c. be successfully imitated but any combination of colours may be produced; for instance, purple, or emerald green, streaked with gold, Siena veined with purple, or any other splendid caprice that fancy may dictate.