Selenetic lime is a mixture of hydraulic lime and plaster-of-Paris, often used for ordinary plastering; its advantages being that it is quicker in setting between the coats, and will take more sand, which renders the mixture cheaper; but it should be mixed according to special instructions from the manufacturers.
Robinsons Patent Paragon Cement (made near Whitehaven), Adamant, and Adamantine are all patent mixtures for plastering, invented and introduced for the purpose of saving time in the drying of ordinary plaster, and with other advantages, such as a better and harder-finished surface, and the properties of being fireproof, and so adhesive and cohesive as to obviate cracked ceilings and the like objectionable but unavoidable results. They are said to be as cheap as the ordinary plastering, though this has to be proved, as a general thing instead of an exception; but the advantages conferred should be worth the extra cost A very superior and economical covering to internal walls is to float them in Portland cement and sand, and finish white with "Albino," the best quality of Adamantine.
External walls are coated in a similar manner to the internal walls, as already explained, with the exception that Portland cement is used instead of "fat" lime, which will not withstand the weather; and they may be finished off in different manners, the chief of which are here given.
Rough-cast has a rough face, made by the last coat consisting of coarse grit.
Ashlar is the lining up of walls, so as to divide the face into rectangles, similar to ashlar or other stone facing.
Stucco is a general term, used for the rough mixtures, whether with cement or lime, cement-covered external walls being often said to be "stuccoed"; while "trowelled stucco" for internal work is a smooth face, worked with fine stuff without hair, in ordinary plaster; and "bastard stucco" contains hair.
Depeter has a more roughened face than rough-cast in external cement plastering; the effect being obtained by small pebbles, which are pressed in while it is setting.
Depreter is a finish to the same cementing, made to imitate tooled stone.
Scagliola is an imitation of marble, in pilasters, etc.
Cornices, and other ornamental mouldings, used to break the angles of apartments, etc., are "run" in plaster by means of "horsed mouldings," running on a wood ground fixed on the wall, truly horizontal, the required depth of the cornice. Ordinary cornices are backed or roughed up with a stronger mixture of coarse stuff, to make it set quicker; and when this has been worked to the right contour it is finished off with plaster-of-Paris, which gives it a hardened white face, with good arrises, where required. When moulded cornices are too big to allow of this backing up being well and properly done in rough stuff, they are scotch-bracketed, as Fig. 884, which consists of laths cut to lengths and fixed from wall to ceiling, to take off the triangular space shown, and fill up the angle to save material.
As the cornices increase in size beyond this, it becomes necessary to use wood bracketing, which consists of wood brackets, roughly cut to the required shape, and fixed, 16 inches apart, to the ceiling joists and wall, and on these the laths are nailed longitudinally for the plastering, as shown in Fig. 885; though sometimes the brackets are so large that they have to be built up in parts and framed together, as Fig. 886.
Enrichments in plaster are cast in moulds made in beeswax, modelled to the required design.
Papier Mache or Carton pierre, as the name implies, is a paper composition formed into the required moulds and ornaments.
Fibrous plaster is a patent, now very much used, consisting of slabs of various sizes, fixed with zinc nails to the woodwork, and covered over with a setting coat about 1/8 of an inch thick. Of this appliance, "Hitchin's," "Jackson's," and "Wilkinson's" are the best-known qualities.
Plaster work is often painted, or treated by the following processes : -
Whitewashing or limewhiting consists of two coats of "fat" lime slaked to a white liquid, and applied with a large brush; it is only used in common work, and for sanitary purposes.
Whitening is a mixture of size and whitening, applied in two coats to internal work only, such as ceilings and walls; and when any colouring matter is added it is called "distempering," the surface being first charcoled or claircolled - i.e., covered with a solution of glue and alum, which fastens the colour, as it were.
Colouring, applied to both external and internal work, consists of ordinary whitewash, mixed with different colouring matters. "Duresco" is a patent washable covering of this class.