PAINTING AND DECORATING Purpose of Painting. Painting serves two well-defined purposes—namely, protection and ornament. Incidentally, it serves also the pur pose of sanitation, for painted surfaces afford poor lodgment for disease germs and filth, and are easily kept clean.
Painting requires the exercise of careful judgment. The condition of the weather, the degree of temperature and moisture, the nature and condition of the surface to which the paint is to be applied, the presence in the air of sul phur and gases from manufacturing industries, or of salt from the adjacent sea coast, the prox imity of foliage, exposure to the sun, etc., all exert a most important influence on the paint film when it is drying. To secure the best results, therefore, the proportioning of the paint should be left largely to the judgment of the experienced painter, although its general com position may be specified by the architect.
Nature of Paint. Paint, properly speaking, is a mixture of a finely divided solid substance or combination of substances, held in suspension in a liquid, which is termed the vehicle, and capable of being spread upon the surface to which it is to be applied, by means of a brush or spraying apparatus. The different solids which are used in paint making are termed pig ments. They do not become paint until they are mixed with the thinner or vehicle. Thus white lead, zinc white, ocher, Prussian blue, and Venetian red are all pigments, but they do not become paints until they have been mixed with linseed oil, turpentine, or other vehicle.
Ready-Mixed Paints. Paint may either be mixed by the painter himself, or it may be obtained already mixed in two different forms— in one as a tinted paste, to which the painter adds thinners as his judgment dictates; or in the other, already thinned and prepared for imme diate application. The latter are known as mixed paints or ready mixed. Good results may be obtained from any of these kinds of paints, provided they are adapted to the work on hand. Generally, however, the experienced painter prefers to mix his own paint, because he can then more perfectly adapt it to meet the peculiar conditions of weather or surface that may con front him. A great deal of painting is done by men who do not possess the requisite experience to mix paint properly, or who lack the color sense that is needed to produce the required tints from the usual pigment colors. For men of this kind the paste or mixed paints are well adapted.
Poor-Quality Paints. There is undoubtedly much prepared or mixed paint on the market which is largely made up of make-weights and extenders, and which possesses little real paint value. Such paint is usually offered for sale at a low price, and, like all cheap things, is apt to be of poor quality. In buying cheap paint or in hiring a cheap painter, the property owner must expect to get as poor results as he would obtain if he buys cheap clothing in which cotton masquerades as wool. Good paint, like every thing else that is good, commands a fair price, and cannot be bought cheap. Good results can be obtained by first-class mixed paints, and just as good results can be obtained by the shop mixed paint of the experienced and honest prac tical painter; but the ready-mixed paint and the shop-mixed paint will differ materially in composition. The painter, as a rule, prefers a paint made of white lead and linseed oil, with the necessary tinting colors—for light tints— and such driers as may be required. The manu facturer finds it practically impossible to put up a pure white lead and linseed oil paint in cans ready for use, because such a paint will almost invariably become "fatty" and unfit for use after standing in stock for some time, and the result obtained from its use in that case would be anything but satisfactory. The use of forty per cent or more of zinc white in a mixed paint, seems to prevent this tendency to become fatty; and, as its use may be defended on other grounds also, it follows that prepared paints are all based to a greater or less extent on zinc white, some of them containing no white lead at all. The best prepared paints are made up of white lead and zinc white, with such colors as may be needed to produce the desired shades, and contain none of the so-called "inert pig ments" (see below under "Ingredients of Paint"), although the use of as much as thirty per cent of barytes is strongly urged by many paint experts.
Variations of Color. By far the greater por tion of the paint used for outdoor painting to day is light in color. The light colors are made by the addition of small proportions of strongly colored pigments to a white base. Where a dark-colored paint is desired, such as a bottle green, a Tuscan or Venetian red, or a deep brown or yellow, no white base is used, but the colored pigment is simply thinned with oil to the consistency required.