WHAT'S REALLY IN A CAN OF PAINT?
Paint
is a creation of man used from the beginning of recorded history -- from the the caves of
Lascaux in France to the ceiling of the Sistine Chapel, on the figureheads of the Spanish
ships which founded the New World, to the decorative symbols on teepees of Native
Americans. It is used for decoration, for communication, as a preservative and as a
maintenance tool. Today, paint has evolved into the protector, preserver and beautifier of
home, workplace, public spaces and even houses of worship.
A thin film of paint -- a few thousanths of an inch thick --
protects, seals, hides, and decorates. Simply put, paint offers long term protection at a
very moderate price. It keeps existing structures from deteriorating and, in so doing,
preserves natural resources such as trees, water, and a variety of energy sources. To
further appreciate the merits of paint, it is important to understand what actually goes
into the can.
Paint is a simple mixture of ingredients including pigments, a
binder and a diluent, or thinner (in latex paint is it water; in solvent paints, it is a
petroleum solvent).
Today's pigments, not unlike the mud, blood and chalk used
centuries ago, provide the texture, color and hiding properties of paint. The pigments,
usually in the form of dry powder, can be organic (containing carbon), inorganic (no
carbon), synthetic or naturally-occurring. Today, with the utmost concern for consumer
safety, architectural coatings are formulated to be as safe as possible by carefully
selecting pigments. No longer in use in consumer paints are pigments which were found to
pose potential health hazards because they contained chromates, lead, soluble barium, or
asbestos.
Titanium dioxide is the primary pigment ingredient that provides
hiding in light color paints. While any powder, even baby powder, can pose a health hazard
if inhaled in high concentrations, titanium dioxide which is also used in cosmetics, soaps
and certain food products, when used in a paint film is not respirable and poses no risk
to the user. Other inert pigments include calcium carbonate (limestone), talc, clay, sand
(silica). All of these are naturally occurring materials that are tightly bound in the
paint film and contribute various properties like gloss control, flow, and film build.
Iron oxides are inorganic color pigments, chemically akin to rust on metal, that are used
to produce reds and yellows.
The binder portion of architectural coatings consist of synthetic
and natural resins which start out as liquids but dry to form tough durable films. The
properties of the binder largely determine the properties of the paint film. In waterborne
coatings the binder is usually a latex emulsion composed of vinyl and/or acrylic
copolymers. In solventborne coatings the binder is usually an alkyd, which is a natural
drying oil modified chemically to be especially tough and long-lasting.
As most people know, today's latex emulsion paints are thinned
with water and represent the ultimate in safety and ease of use. Solvent-based or oil
paints are thinned with petroleum solvent which make them less convenient and require more
care to be used safely. Over the years, use of solventborne paint has diminished because
of concern over volatile organic compounds (VOCs). However, solventborne paints still play
an important role today because of their unique durability and adhesion properties.
Before using any coating carefully read and follow label
instructions.
Other ingredients in paint, called "additives," impart
a variety of properties including flow, stability, drying, defoaming, mildew resistance
and viscosity.
ADDITIVES
Some additives caused health concerns in the past and have been
removed or greatly reduced in modern coatings.
Formaldehyde is no longer added to
paints or resins. At one time, it served as a biocide to prevent bacterial degradation of
the paint. It was replaced over the last decade with ingredients commonly used in
household products and cosmetics.
Mercury which was added to coatings as
a biocide after World War II (when it was also used in medicines) was eliminated from all
paints by Benjamin Moore in 1970. By 1991 mercury in paint was regulated by EPA and was
removed by all manufacturers.
Lead was eliminated from consumer
products by Benjamin Moore more than 20 years ago and by the industry at large over ten
years ago. Lead was used in many forms over the years and provided hiding, color, drying,
and corrosion resistance in architectural and industrial maintenance coatings. By the
1970's lead use was limited to drying, corrosion resistance and some industrial
maintenance colors.
Other additives:
Coalescents (a.k.a. film forming aids)
are solvents used in waterborne coatings which help fuse, or coalesce, latex particles in
latex emulsion paints during the drying process. They make possible better paint films by
permitting the use of harder resins in the coatings formulation. These harder resins
result in interior paints that are scrub resistant and durable.
Anti-skinning agents, used only in
solventborne coatings, prevent undesirable surface drying, or skinning, in the container
during storage and shipment.
Pigment suspending aids, dispersants, and surfactants
are present in most paints in very small quantities. They impart stability and promote
shelf-life.
Viscosity and flow enhancers, provide
superior application properties, as their description implies. They are needed to achieve
the best possible hiding and film appearance.
While solventborne coatings use is on the decline, especially in
the consumer sector, these paints still provide important, unique properties not always
available in waterborne coatings. Properties at which solventborne coatings excel include:
Rust-inhibitive and other special primers, such as stainblockers.
Stains, such as wood stain for furniture refinishing and exterior
semi-transparent finishes.
Varnishes, such as clear finishes for interior use and exterior
varnishes, such as marine.