Guide to Working with Plastics: A Wealth of Fillers and Paints--Plastic-Base Coatings: Paint for Any Purpose

Except in historic restorations, where paints based on linseed or tung oil are still used, most modern coating materials are made of plastics; alkyd- and latex- base paints are practically universal for exterior house painting, and latex is the standard choice for interior work. In addition, a great array of fluid resins, from synthetic rubbers to two-part epoxy coatings, make it possible to coat not just wood or wallboard or masonry, but virtually any surface in or on your house.

You can, For example, give a factory- like finish to plastic, metal or ceramic fixtures—from kitchen-range hoods to bathroom sinks—with polyurethane, vinyl or epoxy coatings that will dry to an ultra-hard sheen or to a rubbery, grease- resistant hide. With virtually no preliminary preparation, you can convert slabs of rough wood—such as barn boards or slices of tree trunk—into attractive table-tops by coating them with a thick, tough, crystal-clear layer of a specially formulated epoxy resin. And tool handles dipped in a rubber-base compound instantly ac quire slip-proof, cushioned grips.

Outside the house, weathered shingle roofs can be covered with flexible alkyd coatings that expand and contract with temperature changes. Clear silicone protects brick walls from the ravages of moisture. Oil-resistant, fast-drying acrylic toppings sheathe driveways; skid-proof compounds based on synthetic rubbers can protect the surfaces of walkways and steps and make them safer to tread on when the day is rainy.

Of course, no single resin can offer every advantage of today’s modern coatings. Yet so versatile are plastic resins that there is usually a selection of coatings for a given job. Making a choice from among the available products is the first crucial step in any painting or sealing job. To guide you in this choice, the box below lists the major families of coatings and indicates the results that each one delivers. Consult the list to see which products seem likely to serve your needs; then, having narrowed your choice, consult the chart at right to see which of these are compatible with the surface that is to be covered. If the surface has previously been painted, you should also consult the chart to find out which of your choices will be compatible with the old coating.

Finally, consider the cost of the materials that are still in the running. You may reject some high-performance coatings— especially those that are based on epoxy, vinyl or urethane resins—as being too expensive for a particular job, even though they might work somewhat better than the runner-up.

Pros and Cons of Frequently Used Finishes

Included in this guide are the eight major families of plastic-base coatings. The descriptions include only those proper ties offered by the product in its most common form. Many large paint stores also carry special formulations—such as polyurethane floor coatings with ad- mixtures of nonskid chips.

--ALKYDS. Available clear or in colors, alkyd-base paints cover easily and are economical. They adhere well to most surfaces except fresh concrete and plaster. Alkyds are durable under normal conditions but deteriorate with excessive exposure to detergents, solvents and corrosive chemicals.

--EPOXIES. These coatings are produced by a chemical reaction between an epoxy resin and a hardening agent, mixed together before application. The mix ture retains its working consistency for 15 minutes to four hours; excess cannot be saved. Epoxy paints, available in all colors, adhere excellently to wood, metal or masonry. They form tough, hard coatings that can withstand abrasion, solvents, detergents and corrosive chemicals. High price limits epoxy to jobs where high performance is a must.

--LATEXES. Latex paints—which are also called acrylic latex—are economical and easy to apply; in addition, they are non-flammable. They resist fading and stand up to light abrasion and corrosion. Latex films breathe, so they resist blistering, but they require thorough surface preparation for good adhesion.

--PHENOLICS. Phenolic resins are most often combined with natural oils to pro vide a versatile, moisture-proof base for clear varnishes and enamels. Such products dry fast and are especially durable in humid environments. They are ex pensive, however, and they are not available in white or light colors because the resins have a yellowish tint.

--POLYURETHANES. Polyurethane coatings cure hard, glossy and tough, with excellent chemical and abrasion resistance. But polyurethanes are highly flammable until they dry, and they are expensive. Because they contain sol vents that attack existing coats of alkyd or latex paint, they cannot be applied over those coatings. Clear polyurethane darkens with long exposure to sunlight.

--SILICONES. Dilute solutions of silicone resin will shield unpainted masonry surfaces against moisture without changing their color or appearance. Higher concentrations may be combined with alkyds and aluminum or carbon pigments to produce stove paints that withstand temperatures up to 1,2000 F.

--SYNTHETIC RUBBER. Chlorinated poly isoprene, polystyrene butadiene, poly vinyl toluene and other resins—synthetic rubbers—all form the basis for many water-resistant coatings. Available in a moderate range of colors, such rubber-base paints seal and decorate swimming pools and masonry; they are a good choice for walls that are subject to condensation or frequent washing.

--VINYLS. Resins derived from polyvinyl chloride and polyvinyl acetate produce flexible coatings with exceptional durability and resistance to water, corrosive chemicals and abrasives. Most commonly available in combination with alkyd resins, vinyl coatings are ideal for metal and masonry surfaces in marine use and where chemical resistance and good appearance are important.

TABLE OF: Matching the Paint to the Stresses It Will Face

--Choosing a paint. Surfaces vary not only in material but in the kind and amount of punishment they must take; the three columns on the left of this chart are in effect a job description of the project. Heavy duty” describes a surface that must be frequently washed or is subject to abrasion. Marine,” high humidity” and corrosive” refer to environment—the first to coastal areas with salty air; the second to places subject to dampness, such as bathrooms; the third to urban locations, where the air may have high proportions of smoke and acidic gases.

Find the line for your project, then read across to the coating column on the right. A dot under a coating means it’s acceptable for the job.

Material | Use | Environment

Wood -- General purpose: Interior

Exterior

Exterior/marine

Heavy duty: Interior

Exterior

Exterior/marine

Floors | Interior

Interior/high abrasion

Metal | General purpose: Interior

Interior/high humidity

Exterior

Heavy duty | Exterior/marine

Exterior/corrosive

Floors and stairways | Interior

Plaster and wallboard | General purpose: Interior

Interior/high humidity

Masonry | General purpose: Interior

Interior/high humidity

Exterior

Heavy duty| Exterior/marine

Exterior/corrosive

Floors: Interior

Interior/high humidity

Interior/heavy traffic

Glass | General purpose: Interior

Plastic| General purpose: Interior

-- Choosing a paint. Surfaces vary not only in material but in the kind and amount of punishment they must take; the three columns on the left of this chart are in effect a job description of the project. Heavy duty" describes a surface that must be frequently washed or is subject to abrasion. Marine," high humidity" and corrosive" refer to environment-the first to coastal areas with salty air; the second to places subject to dampness, such as bathrooms; the third to urban locations, where the air may have high proportions of smoke and acidic gases.

Find the line for your project, then read across to the coating column on the right. A dot under a coating means it’s acceptable for the job.