WATER PAINTS FOR EXTERIOR AND INTERIOR WORK Calcimining. The art of painting upon plas ter with water colors is called "calcimining" or "kalsomining." It is also known as "distemper painting," and is sometimes spoken of as "tint ing." In this class of work the colors are mixed with whiting as the white base, glue being employed as the binder.
Calcimine is prepared by dissolving white sheet glue in hot water, after it has soaked in cold water. A saturated solution of alum in water is made, and is added to a stout paste made by mixing bolted English cliffstone paris white (or whiting of the best grade) in water; and to this the liquid glue is then added as a binder. To color this paint, so-called "distemper" col ors, or colors ground very fine in water, are used. All colors that might be affected by lime must be carefully avoided, such as chrome yel low, chrome green, Prussian blue, etc. The tint ing colors should be added to the whiting before the glue is put in. As the calcimine dries out lighter in color than when it is wet, the only way to test the tint is to dip a piece of white drawing or wrapping paper into the pail, take it out, and dry it. This will show the color as it will look after drying.
The greatest difficulty in the use of calci mine is that it must be put on in a continuously flowing coat, since, if an edge is allowed to dry, or if the painter goes back and touches up the work that is not dry, ugly marks called "laps" will show. In tinting a ceiling, two men (some times three or more) usually work together, be ginning at one end of the room and working continuously toward the other end; and under no circumstances must they stop work until the entire ceiling is completed, or the whole job will be hopelessly ruined.
The prepared calcimines are of two classes— the hot-water and the cold-water. They are put up in powdered form.
Hot-water calcimines are made by using finely ground or powdered animal glue, and in principle do not differ from the shop-mixed calci mines. In mixing hot-water calcimines, boiling water must be used.
Cold-water calcimines, as a rule, are made with a casein binder. Casein is one of the con stituents of skimmed milk. These materials have also given great satisfaction.
In addition to animal glue and casein, there have recently been put on the market a number of vegetable glues that are highly recommended for the preparation of calcimines. The greatest objection to the use of animal glue is that it is apt to decompose in hot weather, and sometimes the smell will cling around the house for weeks.
Water paints depend for their binding upon some other substance than the water, the latter serving merely as a thinner, the same as turpen tine or benzine acts in oil paints. When a water paint has dried, the water has completely evapo rated, leaving the particles of paint held to gether by the binding medium which the paint contained.
Water colors used by artists are made by grinding up the pigment very fine with gum and pressing it in cakes; or else this ground mass is kept moist by the addition of glycerine, making the ordinary moist colors that are put up in tubes or in small china "pans." These colors possess no weather-resisting properties. An other class of pigments ground in water are the distemper or fresco colors, used for painting upon plaster or tinting walls or ceilings. The binder, in this case, is usually glue, which is added when mixing the paint. Such paints can be readily washed off, and are valueless for outside painting.
Whitewash is the oldest form of water paint, although it is not strictly weatherproof. It is much used on the outside of farm buildings, fences, and the like, as well as for the interior of stables, cellars, factories, and similar places. Even when used outdoors, a good coat of white wash will last for a number of months, and it involves so little labor in the application that its renewal is a matter of comparatively little mo ment. Whitewash is made by simply mixing unslaked lime with water, and is applied to the surface in the consistency of thin cream. It will naturally adhere better to a rough surface like brickwork or unplaned lumber than to a smooth board. In drying, the water evaporates, and a coating of lime is left upon the whitewashed sur face. This does not serve to waterproof the wood to which it is applied, since rain will soak into whitewash, but a newly whitewashed house is neat in appearance, and this neatness is re tained for several months. Whitewash, being disinfectant in its nature, is also sanitary and acts as a wood preservative. What is even more important, whitewash is one of the best fire retarders that has yet been discovered. Indeed, if the joists and studding of the newly built house were well whitewashed, and then if the rough sheathing were whitewashed inside and out, and the underside of the board floors given a good heavy coat of whitewash, there would be little opportunity for a fire to gain much head way before it could be extinguished, since fires usually spread in the air spaces that are left between the studs and the floor joists. The ex pense of such a method of fireproofing is very slight, compared with its effectiveness. If a paint spraying machine is used, by which the whitewash is thrown on by air pressure in a thin spray, the whitewash can be applied much thicker, and will penetrate the cracks between the boards and all the nooks and crannies in the bridging of the joists much better than it can be made to do when applied with a brush, ren deriug it even more valuable as a fire retarder.