CASING or' Txmaint-WoRx is when the outside of a timber building is plastered all over with mortar ; after which it is made to resemble stone-work, by striking it, while wet, with the. edge of a trowel, or other implement. guided by a rule. This operation is best performed on heart laths, because the mortar is apt to cause a rapid decay in sap laths. The coating is commonly laid in two thicknesses, the second being applied before the first is dry.
CAST (from the Danish, truster, to throw), in plastering, a piece of insulated plaster, originally formed in a cavity, the bottom of which is the reverse of the thee of the east.
The operation is thus pertbrmed : a small quantity of plaster of Paris is mixed with water in a bacon, or pan, and stirred up with a till thoroughly incorporated ; more plaster is then added by degrees, till the mixture assumes a moderate consistency, such as to flow on all sides when poured on a horizontal surface ; the mould being slightly oiled or greased, to prevent adhesion, the liquid plaster is poured in, so as to fill the mould, or something more. When stitiened in a small degree, the superfluous parts are scraped off to the middle, or in several parts at the edges ; when it begins to heat, which happens in a few minutes, it will be sufficiently hard : then, it' the mould be made of wax, it may be removed by bending it away from the cast, gently at the edges, quite round, using the parts left on the surface as handles ; and proceeding gradually towards the centre, till the cast is quite relieved ; but if the material of the mould be brimstone, a slight knock on the back will relieve it. As this aperation can only be performed in the direction of a straight line, no part of the cast near the bottom of the mould must project from this line to a greater distance than any part more remote, otherwise it cannot be drawn out without breaking such projections. If more relief is required, than what can be given by the mould, the cast must be undercut with a knife.
It' the impression can be relieved of the Mould, the cast may be of one piece ; otherwise it must be made in several segments, and in such manner as may best conceal the jo in ings.
'Plaster casts are sometimes used for mouldings, instead of working them by hand, in situations where they cannot be conveniently run with a mould.
An exact representation of an original piece of sculpture, or C \ en of a living animal, may be taken, whether generally concave or convex, by using the original as a mould ; on which, having first oiled or greased the parts in a slight degree, pour the plaster, as just directed; and this impression is in its turn to be used as a mould, and will give a fac-simile of the original.
Pliny mentions the of faces from nature, as being early in practice among the Greeks.
This useful art supplies the painter and sculptor with exact representations from nature, whether of men, brute animals, draperies, or plants; it multiplies models of all kinds, and is now brought to such perfection, that casts of antique statues are made perfectly similar to their prototypes, except only with respect to colour and materials.
The introduction of plaster in architectural decorations, dates from the prevalence of the style called by us the Elizabethan. but its influence is more conspicuous during
the succeeding or Italian style. It was first employed in carved and paneled wainscoting. and ill the enrichment of the highly-decorated ceilings, which were a prominent feature in buildings of the period. At the first onset, however, the plaster was not east, but each individual ornament moulded by hand, fixed in the situation which it was intended after wards to occupy ; it was indeed merely the substitution of plaster for wood, and the only advantage consisted in the facility with which the former could be carved, whereas the execution of the latter was difficult. This advantage was further extended at the commencement of the eighteenth century, by casting the plaster ornaments in moulds previously prepared for the purpose, so that from a single mould might be produced a number of casts, thus reducing the expense considerably. Sons afterwards allot her material was em ployed in similar decorations ; this was the pulp of paper, which was very generally used, though not so extensively as plaster; through the poverty of the designs in this material, as well as the imperfection in the machinery of those days, it fell into disuse, and was at last entitely superseded by plaster. The latter material, however, could not produce the desired ultimatum, it answered very well so long as the Greek style of ornamentation prevailed ; but when this was superseded by the French, Flemish, and Elizabethan, its defects were seriously felt : it was by no means calculated to express the fantastic forms of the latter, or the luxuriant richness of the former styles, especially when, as was frequently the ease, the design was marked by bold projection and deep undercutting. This difficulty led to a new trial of the carton pierre, or papier mache as it is now called, which, by the aid of improved machinery, and a greater knowledge of chemical and general science, has been advanced to a high state of excellence, and is in every respect superior to plaster casts previously employed. One invaluable advantage it possesses, is, that it preserves the indents and undercutting of the original or mould, however much recessed ; in fact, it can readily be made to assume any form, however intricate. Add to this its hardness and durability, its adaptation to external ornaments, for it is known to have remained unin jured for many years, though exposed to the vicissitudes of the weather; its indestructibility by vermin, its lightness, and its sharpness, and truth of outline, and its superiority to plaster, will not be for a moment questioned. In many of the above particulars, it is superior even to wood, to which it is in some respects similar, for it may he cut with a saw or chisel, bent by heat or steam, and even planed and smoothed with sand-paper. Further, its lightness will allow it to be fixed in any situation, without fear of displacement, and it requires but nails or screws, and even in some eases only needle-points, to secure it firmly in its position. It holds pre-eminence over plaster, in as much as it will receive colour very readily, and gilding much more so than the generality of materials to which such enrichment is applied.