For centuries, paint was essentially lead. Ancient Egyptians, Greeks, and Romans made
a sort of paint by treating lead with wine or vinegar. Later painters mixed up white-lead
paste, then added linseed oil, turpentine, a drier, and colored pigments in oil. Such paint
had turpentine, a drier and colored pigments in oil. Such paint had great hiding power, was
easy to work with, stuck where it was applied, and weathered well.
Unfortunately, it also poisoned people, by skin absorption, respiration, or ingestion
(the paint chips tasted sweet). Today, paint with more than .06 percent lead by volume is
banned in the U.S.
There's also been a shift away from oil as the base for paint. It began during World War II,
when linseed oil and the solvents that cut it were scarce. By the mid-'5Os, synthetic replacements
were outperforming natural ingredients. Today, practically all paints consist of some form of
synthetic resins or polymers.
Modern solvent-thinned paints still work like the old oil-base paints, only more effectively; alkyds
(a hybrid word designating the combination of alcohols and acids that produces the synthetic resins)
have replaced most or all of the natural oils. Alkyd formulations are comparatively low in cost and
have excellent color retention, durability, and flexibility.
But the most dramatic shift has been away from solvent-thinned paints in favor of water-thinned ones.
Today, latex is the consumer standard, accounting for nearly 80 percent of the paint sold.
What's in paint? Three components
Pigment gives paint its color and hiding power.
Vehicle is the combination of synthetic resins and oils that surrounds the pigment particles.
It determines cohesiveness (providing the strength for the dried paint film) as well as adhesiveness.
Carrier (often listed as the volatile vehicle) thins the syrupy resins so the paint will flow on;
it evaporates first as the paint dries, and it allows for varying consistencies thicker or thinner.
Water is the carrier for latex paints, petroleumdistillates for alkyd paints.
Are today's paints better?
Experts disagree. The quality range is much wider, but the best are better and
the worst much worse. Paint life span is impossible to predict; there are too
specific to your situation. Be wary of guarantees in judging a brand, see if
the paint levels itself out, showing few brush or roller marks, ripples, or
pockmarks. It shouldn't run or sag on the wall during application-the sign of
a thin paint (or perhaps you're applying too thick a coat.)
The paint should hide what's underneath it. It should dry hard, to resist
denting, scratching, marring. Hardness correlates with resin content and gloss.
Old-timers might swear by linseed oil base paint, but tests at the USDA's Forest
Products Laboratory suggest that today's best choice for routine outdoor home
use is an acrylic latex with a resin content of at least 20 percent.
Paint Gloss: what you get is what you see
Resin makes paint durable, easy to clean, and moisture resistant; the more
resin, the higher the gloss. High-gloss paint reflects light, emphasizing
defects in walls and ceilings as well as showing off whatever it coats.
(Textured paints and flats break up light; that's why they're used on large
walls and ceilings, particularly if those surfaces are uneven or damaged.
On labels, gloss goes by various names: luster, shine, sheen. Paint can be
termed high-gloss, semi gloss, or flat (mat). Semi gloss can be called eggshell,
velvet, satin, or pearl, and can range from nearly flat to very shiny, depending
on the manufacturer. There's no industry standard.
With enamels, the pigments used should be top quality, with little filler.
Latex glosses may stay tacky much longer than you think. They may feel dry to
the touch, but don't stack things on the newly painted surfpadding:ace too
soon, or they may bond to it. Cure can take two weeks to a month.
Latex Paint: easy to work with, clean up
Once a name for synthetic rubber, latex is now synonymous with water-thinned
paint. The pigment-holding resin particles are held in suspension. Instead of
absorbing oxygen to form a hard coating, the particles actually coalesce into a
tight film that is insoluble in water when dry.
Latex is easy to work with. It can be applied to damp surfaces. It doesn't
require a wet edge; you can stop mid wall, start later, and never see where you
left off. It dries fast, though a full cure can take up to four weeks. Best of
all, you can clean up wet paint with soap and water.
You can tell latex quality by the type of resin used:
acrylic is best; vinyl acrylic and other blends next, all vinyl not as good.
All are flexible (particularly the acrylics), stretching and shrinking with the
wood or whatever they're painted on. On the down side, you can't sand latex
especially gloss latex to a desirable texture; it will tear off or melt to a
gummy consistency. Latex enamel doesn't level as well as alkyd enamel and won't
hold as high a gloss but a top-quality latex product will hold its gloss better
and longer than its alkyd counterpart, especially in areas exposed to weather.
higher gloss, harder surface Alkyd paint (often called oil-base paint) doesn't
dry like latex; oxygen absorbed from the air changes the molecular structure of
the solids, so you can sand an alkyd surface- a critical factor if you're using
successive coats to provide high glosses. The paint will also hang on a little
harder, because the solvent will carry the paint into the substrate more than
water would. On old, poorly prepped surfaces, like chalking walls, choose an alkyd.
It will also hold a higher gloss, and the paint film is more moisture resistant.
On the minus side, alkyds are harder to apply, aren't as sag resistant as latex,
are harder to touch up, and require cleanup with mineral spirits.