Painting is a good way to make wood houses attractive and to freshen or change their appearance. Paint can give wood an endless variety of colors.

The colors are important elements in design. White, or a light color, makes a small house look larger. A dark color makes a large house look smaller. Light tints emphasize attractive parts, and dark shades suppress unattractive parts of a building. Pleasantly contrasting colors can restore harmonious balance among unshapely parts of a building.

The natural color of wood after it has been exposed to the weather for a few months is dark gray, although at high altitudes it is often brown. If the gray color is satisfactory, wood buildings can remain unpainted and the cost of paint maintenance thereby be saved. Buildings unprotected by paint are by no means unusual; in fact, the two oldest frame buildings in the United States, one in Dedham, Mass., and the other in St. Augustine, Fla., have never been painted. Surviving houses of the Amana Society in Iowa still have unpainted wood siding more than three-quarters of a century old.

The decorative program for a wood building should be chosen when the building is first planned. Woodwork to be kept painted should consist of smoothly surfaced boards or plywood. Smooth wood can be painted with a third of the amount of paint and with far less effort than is required for wood with the rough surface left by sawing or splitting. The glossy paints used for house painting need smooth surfaces if the paint is to show to best advantage. On the other hand, unpainted woodwork exposed to the weather soon becomes rough; economy therefore dictates the initial choice of unsurfaced woodwork for such use.

Unpainted woodwork needs to be thicker in dimension and more firmly fastened in place than may always be necessary for well-painted woodwork. The weather, by alternately wetting and drying the exposed surfaces of boards more rapidly than the moisture content can readjust itself within the boards, sets up severe internal stresses within the wood. The outcome is, successively, a roughening of the wood grain; wood checking; a tendency for boards to cup, to withdraw nails, and to split if they are unduly thin or short; and a tearing loose of wood fibers from the surface at such a rate that boards lose as much as one-fourth inch of thickness a century. For exposure without painting, boards should not be thinner than one-eighth their width nor shorter than four times their width; they should be kept firmly fastened with hardware that withstands corrosion without painting.

A coating of house paint on exposed wood surfaces prevents weathering by slowing down the entrance or exit of moisture enough to keep nearly equal moisture content from the center to the surface of the boards. Internal stresses are thus avoided, and the boards stay flat and keep their smooth surfaces.

With white paint, which should be renewed every 5 years, it may take 50 gallons of paint a century for each 1,000 square feet of surface to prevent the weathering away of wood. It is cheaper, of course, to omit the paint and let the wood waste away slowly, but the better appearance makes painting worth its moderate cost.

Transparent finishes sometimes are favored. The grain and color of freshly cut and smoothly surfaced wood are attractive enough to appeal to persons who like the unusual. In consequence, there is a demand for a transparent protective coating that will serve, as paint does, in preventing wood weathering and yet will not conceal the wood.

Spar varnish is one way to do it, but modernists seldom want the glossiness of a varnish finish. For that reason, linseed oil or certain proprietary oils or wood sealers, sometimes called log oils, have become popular.

The oils and sealers penetrate into the surface of wood instead of overlaying it with a coating as paint and varnish do; because the barrier against the weather is imperfect when little or no coating is interposed, the oils and sealers furnish less protection than varnish and much less than paint. Also, because the transparent finishes are less durable than paint, they must be renewed about once a year or oftener. A century's protection for 1,000 square feet of surface, therefore, may require 200 to 250 gallons of oil, sealer, or varnish, whereas 50 gallons of paint does the job more effectively. It is no wonder our thrifty ancestors preferred paint when they wanted smooth woodwork!

The transparent exterior finishes have two further disadvantages.

First, if they are allowed to go too long before renewal, the wood begins to turn gray from weathering. Once that happens, renewal of finish must begin with tedious scraping or sanding away of the weathered wood to regain a bright surface.

Second, the transparent finishes are readily attacked by fungi, which discolor the surfaces badly. The danger of fungus attack, or mildew, can be reduced greatly by putting a suitable preservative in the oil, sealer, or varnish. Proprietary sealers and varnishes containing a preservative are sold in paint stores. When linseed oil is used, the preservative, pentachlorophenol, can be dissolved in it to the extent of 5 percent by weight. If the wood contains sapwood, in which discoloring fungi grow readily if the wood becomes damp, the wood may well be treated with a commercial water-repellent preservative before the transparent finish is applied.

Rough, unsurfaced wood, which may be unduly expensive to paint, may nevertheless be colored other than the gray of weather-beaten wood. Shingle stains are inexpensive kinds of paint. They are made with pigments, linseed oil, and much volatile thinner; they are thin enough to be applied easily to rough wood, and they impart color without glossiness and without seriously obscuring the rough texture of the surface. A preservative, such as creosote or a pale distillate from creosote, is often added to shingle stain.

Although paint prevents the weathering of wood, paint cannot be relied on to prevent decay. Decay comes from the action of fungi on damp wood. Nearly always it starts on unpainted concealed surfaces and it continues usually well within the wood at a distance from the painted surface. Paint, in fact, even hastens decay if water enters the wood at unpainted joints or concealed faces and can only dry out through the painted surfaces. The paint then slows the drying and keeps the wood damp longer. Decay in buildings is prevented chiefly by taking care that masonry or other rot-resistant material is used for all contacts with damp ground or other continuing source of moisture and by seeing that all woodwork will either remain dry or dry out promptly after it is exposed to water for a short time. If wood must be used in damp places, it should be the heartwood only of naturally durable woods or wood that has been thoroughly impregnated with wood preservative.

A PAINTING PROGRAM should be planned before a house is finished—once it has been decided to build with smooth surfaced woodwork.

The principal items in a painting program are a suitable kind of paint, a reasonable schedule for repainting, and the proper amount of paint to be applied at each painting.

The ideal program is one of repair and renewal of coatings before they break up badly enough to require replacement. Over-all economy comes from anticipating and forestalling serious failures. Too often paint maintenance is left entirely unplanned, and each job is done on the spur of the moment, perhaps after the coating has come loose. The cost of repainting is therefore higher and one is prone to malign paint as being less predictable in performance than almost anything else about the house.

The most popular color for homes is white. Most wood homes are small and need the emphasis of white or a light color. For white paint of good quality, properly applied, the reasonable schedule of maintenance calls for repainting every 4 or 5 years. On some woods that are more difficult than others to paint well, special care is needed to meet that schedule.

As I described in Wood Properties and Paint Durability, Miscellaneous Publication No. 629 of the Department of Agriculture, the heavier softwoods, like southern yellow pine and Douglas-fir, need a carefully chosen priming paint the first time the wood is painted. Aluminum house paint is the best priming paint for the purpose. One should be sure, however, that it is aluminum house paint, not aluminum paint for some other purpose. Two coats of white paint, or paint of light color, are then needed over the aluminum paint. If the coating is then maintained by repainting before it wears away too badly, the aluminum paint need not be used again. Next best to aluminum house paint for priming the heavier softwoods are the modern house-paint primers that contain no zinc oxide and that have the property commonly called "controlled penetration." Most dealers in house paint now sell such primers.

White is popular although it is less durable than good paints of other colors. Paints of colors like cream, light yellow, light gray, buff, and tan, that are light enough to have much the same accentuating effect as white, will last a year or so longer than white paint and thus fit a schedule of repainting every 5 or 6 years. Such light colors, called tints, are made by adding very small proportions (usually less than 5 percent by weight) of colored pigments to a white paint. The added durability is remarkably great for such a slight difference in composition.

Still greater durability, one that permits longer intervals between repaintings, can be obtained with paints made with large proportions of colored pigments and little or no white pigment. Colored-pigment paints, except for some brilliant yellows and reds, are dark paints that tend to suppress rather than to accentuate. The brilliant yellows and the reds are too gaudy for use on anything larger than minor areas of trim on buildings; besides, they make relatively expensive paints. Duller, more grayish yellows, reds, maroons, and browns, which are made from pigments containing iron oxide, are appropriate for the body color of some buildings. Paints of such colors may be moderate in cost and of exceptionally long life; with the best of them, a schedule of repainting at intervals as long as 10 years, is practicable.

Because the single-family home is usually a fairly small building, the popular choice of white or a light color to accentuate it is appropriate even though it commits the owner to more frequent repainting than might otherwise be necessary. Brightly painted homes, of course, may have the paints of dark color for contrast on trim or on parts that need toning down. The schedule of maintenance, however, is usually fixed by the requirements of the least durable paint because convenience is likely to dictate that all repainting be done at one time.

THE FARM HOME is often a small house in the midst of a group of larger buildings. The American tradition most appropriately has been to emphasize the home with white paint, but to offset the dominating size of the farm buildings by painting them dark red, relieved by contrasting touches of white trim. The home is thus made the center of the picture; the barns are reduced to supporting background; and the whole conforms to the philosophy of farming as a way of life. The scheme permits an economical painting program of once in 4 or 5 years for the house, and once in 8 or 10 years for the larger area presented by the farm buildings.

Recently a vogue has developed for painting farm buildings white. Perhaps it is to be interpreted philosophically as a shift to the concept of farming as primarily a business in which the housing of cows is more important than the housing of humans. Certainly if barns are to be accented with bright paint, they should be made architecturally more attractive than they generally have been in years past. Judging from experience, in which many farmers have been unable to keep up with the moderate 10-year program for red paint, it seems unlikely that a 5-year program with white paint will prove generally practicable. Besides, a white building badly in need of repainting calls attention to itself far more forcefully than does a modestly dark-red building in a like condition.

OF THE MANY WAYS OF MAKING PAINT, some make more durable or more reliable paint than others. No one way is superior to the others in every respect, for an improvement in one property usually necessitates some sacrifice in another. For example: Old-fashioned, pure white lead paint is more reliable in performance and wears out by a fine crumbling that makes it stand postponement of repainting longer than other white paints will, but white lead paint has the disadvantage of becoming more grimy with dirt than some other paints do. On the other hand, the more recent paints made with titanium dioxide, zinc oxide, and white lead, together with other necessary pigments and liquids, remain relatively clean and bright in appearance. They do not, however, retain color so well and, if repainting is postponed beyond the proper time, they look shabbier and are more troublesome to prepare for repainting than white lead paint.

Home owners who plan their maintenance programs carefully and stick to them can take full advantage of the newer paints, but those who may neglect their repainting would be wiser to use white lead paint.

CORRECT THICKNESS of coating is necessary for reliable performance of the paint. For linseed-oil house paints, experience has shown that correct thickness is about 0.005 inch. Coatings much thinner than that wear away sooner than is necessary; coatings much thicker than that are unduly brittle and are likely to behave badly. A common mistake the first time a house is painted is to apply too little paint. Thereafter, in maintaining the coating, the tendency in towns and cities (although less often on farms) is to paint too often or with too much new paint at a time.

For painting new woodwork it takes about 3.6 gallons of prewar house paints, which are rich in linseed oil, to leave a coating 0.005 inch thick on 1,000 square feet of surface. It can be done either with three coats of about 1.2 gallons each or, if the paint is of the best quality, with two coats of 1.8 gallons each. Present paints, however, usually contain less linseed oil and more volatile thinner than the prewar paints. It therefore takes about 4.5 gallons (three coats of 1.5 gallons each) to leave the desired 0.005 inch of coating on 1,000 square feet. Two coats with such paint would require 2.25 gallons each, which is more paint than it is practicable to apply on smooth surfaces at one time.

REPAINTING should not be done until much of the coating has worn away, say 0.002 inch of the original 0.005 inch. The repainting should then restore the lost thickness but not much more. That can be done with 1.4 gallons of prewar paint, or 1.8 gallons of present paint, on 1,000 square feet of surface. The repainting in such cases can be done with one heavy coat or two thin ones.

The present method of selling paints by trade brands without conforming to trade standards of any kind makes it exceedingly difficult for paint users to exercise choice in selecting kinds of paint or to learn how they are best used. The manufacturers' directions for applying paint, for example, fail to indicate the important difference in the methods of applying the prewar and the present paints. The user is allowed to assume that he may properly spread the present paints over as much surface as he formerly did the prewar paints. Most responsible paint manufacturers report the composition of their paints on the labels, as the laws of some States require, but the formulas are stated in a complicated, highly technical manner. Paint users, who are able and willing to learn how, can get the needed information from the formulas by calculations. Methods of making the calculations are described in my booklet, Classification of House and Barn Paints, Technical Bulletin 804 of the Department of Agriculture. The bulletin points out a method of classifying paints by group, type, and grade that, if adopted by the industry, would simplify the explanation of paint to paint users and permit painting programs for buildings to be set forth in a reasonably simple manner.

THIS CLASSIFICATION of native woods for relative ability to hold paint coatings may be helpful.

Type A are paints that wear out by checking and crumbling, such as pure white lead paint.

Type B are paints that wear out by cracking, curling, and flaking, such as paints containing zinc oxide mixed with other pigments.

Group 1—Woods on which paints of types A and B last longest.

Softwoods:

Alaska-cedar. Incense-cedar. Northern white-cedar. Port-Orford-cedar. Southern cedar. Western redcedar. Baldcypress. Redwood.

Group 2—Woods on which paints of type B wear out faster than they do on woods of group 1, through paints of type A last as long as they do on woods of group 1:

Softwoods:

Eastern white pine. Western white pine. Sugar pine.

Group 3—Woods on which paints of types A and B wear out more rapidly than they do on groups 1 or 2:

Hardwoods:

Aspen. Basswood. Cottonwood. Magnolia. Yellow-poplar.

Softwoods:

White fir. Eastern hemlock. Western hemlock. Lodgepole pine. Ponderosa pine. Eastern spruce. Engelmann spruce. Sitka spruce.

Group 4—Woods on which paints of types A and B wear out more rapidly than they do on woods of group 3:

Hardwoods:

Beech. Birch. Blackgum. Maple. Redgum. Tupelo gum.

Softwoods:

Douglas-fir. Red pine. Southern yellow pine. Tamarack. Western larch.

Group 5—Woods unsuitable for conventional house painting because wood filler is required before painting to fill the large pores properly:

All hardwoods with pores larger than those in birch, as ash, chestnut, elm, hickory, oak, walnut.

Charles F. Brannan

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