Under this head the following few varieties deserve notice: -
Composed of 2 parts washed graphite, 2 red-lead, 16 freshly-prepared cement, 16 barium sulphate, 4 lead protoxide, 2 alcoholized white litharge. The paint must be put on as soon as the roofing is securely fastened, choosing the dry season and a sunny day. Care must be taken to put it on well over the joints; it is recommended that an extra coating should be given to the portions that overlap each other, so as to render them watertight. As a rule, two coats are put on. The first, whilst still wet, is covered with an even layer of fine dry sand sprinkled over it through a sieve. This is done bit by bit, as the roof is painted, so as to prevent the workmen stepping on the wet paint. The second coat is put on about a week later, the sand which has not stuck fast being first swept off. The second coat is not sanded. It is merely intended to combine with the under-coat and form a durable waterproof surface, which will prevent the evaporation of the tar-oil, the usual cause of the failure of carton-pierre roofing, and present a good appearance as well. (Mack.)
Do not mix the gold size and powder together, but go over the article to be gilded with the size alone, giving an even and moderate coating. Let it dry (which will not take long) till it is just sticky, or, as gilders call it, "tacky." Then over a sheet of smooth writing-paper dust on the dry gold powder by means of a. stout, soft, sable brush.
The * Photographisches Wochenblatt' mentions that Spangen-berger has a paint composed of pulverized iron and linseed-oil varnish. It is intended for painting damp walls, kettles, outer walls, or any place or vessel exposed to the action of the open air and weather. Should the article be exposed to frequent changes of temperature, linseed-oil varnish and amber varnish should be mixed with the paint intended for the first 2 coats, without the addition of any artificial drying medium. The first coat should be applied rather thin, the second a little thicker, and the last in a rather fluid state. It is not necessary to free iron from rust, grease, etc, by means of acid before applying the paint, as a superficial cleaning is sufficient. The paint is equally adapted as a weather-proof coating for iron, wood, and stone.
(a) For deal floors, wood, stone, and brick work. Dissolve 15 dr. good glue by boiling with thickish milk of lime, which contains 1 lb. caustic lime. Then add linseed-oil, just sufficient to form a soap with the lime. This mixture can be used for making up any colour which is not altered by lime. A solution of shellac in borax can be added for brown-red or brown-yellow colours, and is very suitable in painting deal floors. With a coating of varnish or lake, the substances thus painted assume a fine lustre. They can be polished with linseed-oil or turpentine.
(ft) A lime paint which will bear washing. 3 parts flint, 3 marble fragments and sandstone, 2 calcined white china-clay, and 2 slaked lime, all in powder, furnish a paint to which chosen colours, that may be employed with lime, are added. This paint, by repeated applications, becomes as hard as stone*, without losing porosity.
When the surface to be painted is of a mineral nature, such as the exterior of a house, the pigments may be mixed with a vehicle consisting chiefly of water-glass, or soda or potash silicate. This method of painting requires some care, and a knowledge of the chemical nature of the pigments used. Some colours are completely destroyed by the alkali contained in the water-glass. Among those pigments which are not altered by the alkali may be mentioned lime carbonate, baryta-white, zinc - white, cadmium - yellow, Naples-yellow, baryta chromate, chrome-red, red ultramarine, blue ultramarine, cobalt-blue, cobalt-green, chrome-green, ivory-black. When a wall is to be painted, it should first be prepared with a mortar composed of pure fat lime and clean sharp sand. The water used should also be free from saline impurities, as these might subsequently effloresce and destroy the surface of the paint. When the surface of this plaster is dry, a weak solution of water-glass should be applied, and the operation repeated several times.
A strong solution cannot be used, because it forms a thin skin on the surface of the plaster, which closes the pores, and prevents the penetration of the water-glass. The pigments are rubbed down with a very weak solution of water-glass, and applied in the ordinary manner. When thoroughly dry, the painted surface is treated with a warm solution of potash silicate applied in the form of a spray. Soda silicate may also be used, but the soda carbonate which is then formed is liable to cause efflorescence. A pigment fixed on the surface of a wall in this manner is as durable as the wall itself, and can be exposed to the weather without any fear of deterioration.
If in a position to coat the glass before putting in frame, excellent effects may be got by using ordinary shellac varnish (made with bleached shellac) tinted with aniline dye. The glass must be slightly warmed before applying the varnish. The strongest spirit of wine should be used for dissolving the shellac and the powdered (not liquid) aniline colours. Sufficient of the colour must be added to the varnish to give the required tint: 1 part of shellac to 8 of spirit is a good proportion. Methylated spirit will do. The varnish should be poured on and placed evenly over the glass (not painted on), and the superfluous quantity returned to the bottle.