By Kevin Le
Interior painting requires as careful preparation of surfaces as does exterior painting. The advent of odorless paints now makes it possible to paint any time of the year. Formerly, most interior painting in the home was done in the fall or spring, when it was possible to leave the windows open to ventilate the room. But open windows brought dust into the room to mar the finished painted surface.
A good interior paint job is often 50% preparation and 50% painting. Do not rush in preparing the surfaces in your eagerness to get at the brush or roller. If you do not prepare the surfaces properly, you'll be back with the paint brush or roller in a few months.
In this section you will find the necessary information on the application of different types of paints on various interior wall, ceiling and floor materials.
Plaster
New dry plaster in good condition, which is to be finished with a paint other than water paint, should be given a coat of primer-sealer and allowed to dry thoroughly before being inspected for uniformity of appearance. Variations in gloss and color differences in the case of tinted primers indicate whether or not the whole surface has been completely sealed. If not, a second coat of primer-sealer should be applied. If only a few "suction spots" are apparent, a second coat over these areas may be sufficient.
A flat, semi-gloss, or high-gloss finish may be applied to the primed surface. For a flat finish, two coats of flat wall paint should follow the priming coat. For a semi-gloss finish, one coat of flat wall paint and one coat of semi-gloss paint should be applied to the primed surface. For a high-gloss finish, one coat of semi-gloss paint and one coat of high-gloss enamel should be used over the priming coat.
Before applying water paints of the calcimine type to new plastered walls they should be sized, using either a glue-water size or, if the plaster is dry, a thin varnish or primer-sealer.
Cold water paints of the casein type may be applied either directly to a plastered surface, or the surface may be first given a coat of primer-sealer to equalize uneven suction effects. The same is true of resin-emulsion paints, with the recommendations of the manufacturer of the product being given preference in case of doubt. Since resin-emulsion paints usually contain some oil in the binder, they should ordinarily be applied only to plaster which has dried thoroughly.
Texture wall paints may also be used on plaster surfaces. The advantages of this type of paint are that one coat economically produces a textured decoration and relieves the monotony of smooth flat paint. It also covers cracks or patches in the plaster more completely than ordinary wall paint. The disadvantages of texture wall paint are that they Collect dust and are difficult to restore to a smooth finish. These materials are available as water-or oil-based paints, are thicker than ordinary wall paints, and may be applied to wallboard as well as plaster to produce textured effects such as random, Spanish, mission, and multicolored.
Composition Wallboard
Composition wallboard usually presents no particular painting difficulties if the ordinary precautions are observed, such as making certain that the surface is dry and free from grease and oil. The painting procedure for wallboard is the same as for plaster; it requires a priming and sealing coat followed by whatever finishes coats are desired, or may be given one-coat flat or resin-emulsion type paint.
Wallpaper
Water-thinned paint may be applied to wallpaper that is well- bonded to the wall and does not contain dyes which may bleed into the paint. One thickness of wallpaper is preferable for paint application. Paints other than those of the water-thinned type may also be applied to wallpaper by following the directions given for painting plaster. However, wallpaper coated with such a paint is difficult to remove without injury to the plaster.
Wood Walls and Trim
New interior walls and wood trim should be smoothed with sand-paper and dusted before painting or varnishing. To preserve the grain of the wood, the surface may be rubbed with linseed oil, varnished or shellacked, and waxed. If an opaque finish is desired, semi-gloss paint thinned with 1 pint of turpen-tine per gallon of paint or the primer-sealer previously described for walls may be used as a priming coat on wood. One or two coats of semi-gloss paint should then be applied over the thoroughly dry prime coat, or if a full-gloss finish is desired, the last coat should be a high-gloss enamel.
Masonry Walls and Ceilings
Interior masonry walls and ceilings above grade may, in general, be painted in much the same manner as plaster surfaces. Here again, it is necessary to allow adequate time for the masonry to dry before applying paint and, in addition, attention should be given to the preparation of the surface. When decorating a wall containing Portland cement (concrete, for example), it is essential to take precautions against the attack of alkali. For this purpose, alkali-resistant primers such as rubber-base paints may be used when oil paints are to follow.
Cement-water paints are best suited for application to basement walls which are damp as a result of leakage or condensation. To apply these paints, the same procedure should be followed as is described here for painting exterior masonry walls.
Concrete Floors
Two general types of paints for concrete floors are varnish and rubber-base paint. Each has its limitations and the finish cannot be patched without the patched area showing through. Floor and deck enamel of the varnish type gives good service on concrete floors above grade where there is no moisture present.
Rubber-base paints, which dry to a hard semi-gloss finish, may be used on concrete floors below grade, providing the floor is not continually damp from seepage and condensation.
Paint should not be applied to a concrete basement floor until the concrete has aged for at least a year. The floor should be dry when painted, the best time for application being during the winter or early spring (assuming there is some heating apparatus in the basement), when the humidity in the basement is low. In general, three coats of paint are required on an unpainted floor, and the first coat should be thin to secure good penetration. After the paint is dry, it should be protected with a coat of floor wax.
In repainting concrete floors, where the existing paint has been waxed and is in good condition except for some worn areas, the surface should be scrubbed with cloths saturated with turpentine or petroleum spirits and rubbed with steel wool while wet, to remove all wax before repainting. If this is not done, the paint will not adhere and dry satisfactorily, if the old paint is badly worn, it should be removed by treating with a solution of 2 lbs. of caustic soda (household lye) to 1 gallon of hot water. This may be mopped on the surface and allowed to remain for 30 minutes after which the floor can be washed with hot water and scraped with a wide steel scraper. Another method of application is to spread a thin layer of sawdust, which has been soaked in caustic solution over the floor and allow it to stand overnight. The following morning, the floor can be washed with hot water and the paint scraped off. The surface should then be rinsed thoroughly with clean water.
If rubber-base paint has been used, the caustic soda treatment may not be effective and it may be necessary to use an organic solvent type of paint remover.
Caution: - When using caustic soda or lye, avoid splashing eyes, skin, and clothing.
Interior Metal
Interior metal, such as heating grilles, radiators, and exposed water pipes, should be painted to prevent rust and to make them as inconspicuous as possible. New metal should be cleaned of grease and dirt by washing with mineral spirits, and any rust should be removed by sanding, after which a metal primer should be applied. The finish coat may be either a flat wall paint or a semi-gloss enamel.
If you are not sure of the primer to use on metal, the paint dealer or manufacturer will give you this information, dependent on the type of metal to be painted.
Usually on exposed air ducts of galvanized metal a primer coat of zinc dust-zinc oxide paint is used, before the finish coat is applied.
The paints may be applied by brush or spray; the small spray attachment for vacuum cleaners is very convenient, especially for painting radiators.
Brass lighting fixtures and andirons may be polished and kept bright by coating with metal lacquers. The lacquers, held in cans under pressure, may be sprayed directly from the container. Old-fashioned or unattractive lighting fixtures may be painted with ceiling or wall paint to harmonize with the surrounding surfaces.
Special Surfaces
WHITEWASH
Whitewashes and lime paints must be thin when applied. In fact, best results will be obtained if the application is so thin that the surface to which it is applied may easily be seen through the film while it is wet. The coating will dry opaque, but two thin Coats will give better results than one thick coat.
A large whitewash brush is best for applying the wash. One should not attempt to brush out the coating, as in applying oil paint, but simply spread the whitewash on as evenly and quickly as possible.
The principal ingredient in whitewash is lime paste. A satisfactory paste can be made with hydrated lime, but better results are obtained by using quicklime paste that has been slaked with enough water to make it moderately stiff. The lime paste should be kept in a loosely covered container for at least several days. Eight gallons of stiff lime paste can be made by slaking 25 lbs. of quicklime in 10 gallons of water, or by soaking 50 lbs. of hydrated lime in 6 gallons of water. After soaking, the paste should be strained through a fine screen to remove lumps or foreign matter.
Whitewash can be made from various combinations of lime paste and other ingredients. The following two formulas are satisfactory.
The casein, which serves as the glue binder, should be soaked in 2 gallons of hot water until thoroughly softened, which should be approximately 2 hours. After dissolving the trisodium phosphate in 1 gallon of water it should be added to the casein, stirring the mixture until the casein dissolves. This solution should be mixed with the lime paste and 3 gallons of water.
The salt and alum should be dis-solved in 4 gallons of hot water, after which the molasses may be added to the mixture. The resulting clear solution is then added to the lime paste, stirred vigorously, and thinned with water to the desired consistency. This whitewash has a yellow tinge when first applied, but the color disappears in a few days leaving a white film.
Another satisfactory whitewash can be made by diluting a moderately heavy cold lime paste (about 33 lbs. of hydrated lime and 8 gallons of water) with 5 gallons of skim-milk.
The area covered by a gallon of whitewash depends upon the nature of the surface, but ordinarily a gallon will cover about 225 sq. ft. on wood, about 180 sq. ft. on brick, and about 270 sq. ft. on plaster. The formulas mentioned will make from 10 to 14 gallons of whitewash. If a smaller quantity is desired, the amount of each ingredient should be reduced proportionately.
STIPPLING
Whether you desire the effect of stippling (tiny paint dots) as a decorative effect, or if you have a wall which has an uneven surface and you feel you can hide the defect by stippling it, you may accomplish this result very simply.
For stippling you need a special brush; get one that is flat, and has short, stiff bristles.
The first step is to cover the surface with a coat of paint, using your regular paint brush, or spray, or roller. Then, while the surface is still wet, take the dry stipple brush and energetically with short strokes drive the ends or the bristles into the wet paint. Be sure not to brush across. The result will be clusters of dots. Every few minutes wipe the brush with a cloth, to keep the bristle ends clean and dry.
STENCILING
You may want designs on the walls, or perhaps even on floors and ceilings, in some of the rooms or hallway. You may buy or make your own stencils, which should be on heavy paper, stencil board, plastic, or metal. Avoid stencils made of lightweight paper which will get soaked when touched by wet paint. Your paint dealer will suggest the best paint for you to use, as it will depend a great deal on the surface over which you want to put the stenciled designs. Generally a heavy paint is used, so that it will not spread under the stencil while you are applying it.
The stencil must be held very firmly against the surface with one hand, and the stencil brush worked over it quickly with the other hand. Or, if you have an assistant, it is best for one person to keep the stencil steady, while the other does the painting. In removing the stencil, make sure you pick it up without smudging.
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