Housing...Inside and Out

October 9, 1998
The Basic Types of Paint

Paint is a mixture of three substances: Solid pigments that contain the color; a liquid agent that bonds the pigment to the surface; and a solvent that makes the paint easy to apply but then evaporates, leaving behind the color.

The three basic types of paints are water-base latex, alkyd and enamel (not a true paint).

The water-base or latex paints may also be called vinyl or acrylic base paints depending on the ingredients used. Water is the solvent. As it evaporates the color remains.

The advantages of water-base latex paint are: easy to apply with no lap marks, fast drying, little odor and fumes, easy clean-up, easy touch-up, non-flammable and any paint can be applied over it. It is also non-toxic.

The disadvantages include: one coat may not cover the surface entirely, it may look dull, it may rust many metals, and some colors will yellow with age.

Water-base latex paint should be used on drywall, plaster, masonry walls and most surfaces painted with flat oil or latex paints. It should also not be used on raw wood since water tends to swell the wood and the surface will become rough. You should not paint over wallpaper either, since water will loosen the paper.

For alkyd type paint, usually an oil-base blend is used to suspend the resins and pigments. Alkyd-base paint is durable, scrubbable, provides a rigid, smoother finish, is good for covering surface imperfections, and usually requires only one coat because of the higher pigment concentration.

It is more difficult to apply and has a slight odor. Alkyd-base paint may darken over time. It also takes longer to dry.

It can be used on wood, plywood, particleboard, hardboard and any painted or wallpapered surfaces. It is also best to use in areas that are susceptible to wear and dirt such as kitchens, bathrooms and woodworking areas.

It should not be used on bare masonry, plaster or bare wallboard since it will raise the nap on the paper.

Enamels are made with a varnish or resin base and are not true paints. However, they are often mentioned as a type of paint.

Enamels are very tough and can withstand extensive cleaning. They are also water-resistant. A disadvantage is that enamels do require an undercoat unless the surface that is being painted already has a finish.

As you select the color and correct paint for the surface, you will notice that you have to make another choice - the finish of the paint. A number of finishes are available for both solvent and water-thinned types. Select the one appropriate to the surface use and appearance.

Gloss paint has a high shine and is especially good for areas requiring frequent cleaning. The high proportion of resins binds the ingredients together and helps them stick to the wall.

Semi-gloss is not shiny nor flat either. It has moderate durability.

Flat is a low glare type of finish. There is no shine whatsoever. It does not pick up reflections but it is very appropriate for cracked or uneven surfaces. Finishes called eggshell, satin, sheen or silk are similar and are flat finishes.


Written by Dr. Francis Graham (Retired)

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