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.