USES OF PAINT Quantity of Paint to Use.—To esti mate the quantity of paint required, divide the number of square feet of surface by 200. The quotient is the number of gallons of paint required to give two coats.
Or divide the number of square feet of surface by 18. The quotient is the number of pounds of pure ground white lead required to give three coats.
Another rule is that new woodwork requires about 1 pound of paint to the square yard for three coats.
But the rules vary according to the nature of the surface and its condi tion, the temperature, and the like.
Old woodwork, especially if unpaint ed or if the paint has been allowed to wear off, will absorb more paint than new wood. Some kinds of wood take more paint than others, and sur faces of stone, brick, or metal may take less than wood.
Rules for House Painting. — The best time to paint houses, barns, and other surfaces exposed to the sun is in winter when the ground is frozen. In summer the heat of the sun opens the pores of wood and other materials, which causes the oil to soak in, leav ing the pigments exposed on the sur face. This may be prevented by first going over the surface with raw oil; but paint applied when the sueface is contracted by cold in winter dries slowly, forms a hard, tough coat like glass, and will last twice as long as if applied at any other time of the year.
Another advantage of painting in cold weather is the absence of flies and other insects, and also the fact that there is much less dust. Paint ing may, of course, be done indoors at any time of the year, but it must be understood that a hot surface will absorb more paint than a cold one and should be first primed with a coat of raw linseed oil.
Buy, if possible, the best white lead and other pigments and the best oil, and mix the paint yourself.
To paint new wood for the first time requires four or five operations —knotting, priming, and two or three coats of paint. Old woodwork pre viously painted requires washing to remove the grease, and may require burning or other process to remove the paint, as well as refinishing the surface before the priming and fresh coats of paint are laid on.
Or it may be sufficient to wash the surface to remove all grease spots, and to lay a fresh coat over the old paint.
Keep up the paint on all surfaces that require painting. It is much cheaper after the original foundation has been laid to go over the wood work with a thin coat of paint quite frequently, than to wait until the paint is all worn off in spots and the wood work underneath is affected with dry rot.
Recoat standing woodwork at least once in two years, and go over win dow sills and sashes as often as they require it.
Prepare paint to suit the purpose for which it is intended. Do not at tempt to make one kind of paint serve every purpose. One kind of paint is required for the outside of a house and another for the inside; and there are special paints for iron, stone, brick, and other surfaces.
Knotting.—The knots in pine boards and other resinous woods con tain turpentine, and unless they are " killed " the turpentine will ooze out and destroy the paint. Hence to kill knots apply with a brush a mix ture of red and white lead ground with water and mixed with a strong glue size consisting of 2 to 4 ounces of glue to 1 gallon of water. Apply while warm to the knots with a brush. Follow with a second coat composed of 3 parts of white lead ground in oil and I part of red lead or litharge. When bone-dry, rub down with pumice stone.
Priming.—After knotting, go over the surface with a very thin coat of priming, which consists of white lead with a very small quantity of dryer, as red lead or litharge, mixed with raw linseed oil. Use 1 pound of this priming for IS or 20 square yards. Have no more oil than is necessary to make the lead work readily, but apply repeatedly and work the coat ing out thin with a brush.
Do not use a lot of thin priming.