Painting

Painting contractors in the United States

Paint and Varnish, liquids that solidify when exposed to air, used to cover surfaces for decoration and protection.

History The first uses of paint were entirely decorative. Iron oxide was used in cave paintings from about the 14,000s BC, and ancient peoples made paints using pigments from ores and from organic compounds. The Chinese used lacquers to paint buildings about the 100s BC. In Europe, protective painting began about the 12th century AD. Prepared paint made of pigments and paint vehicles first became commercially available in the 19th century.

Chemical Composition of Paints Modern paint contains several different chemical compounds. The vehicle forms an adherent coating. When vehicles are exposed to the oxygen in the air, their molecular structures change, forming a tough film. The pigment is dispersed in the vehicle, giving paint its color and hiding power. Pigment is a fine powder that either strongly scatters light, yielding white, or absorbs certain wavelengths of light, producing a color. The solvent, or thinner, evaporates shortly after the paint has been applied. Solvents may be turpentine or may be an alcohol, a ketone, or an ester.

In water-thinned latex paint, introduced in 1949, the synthetic vehicle is emulsified (suspended as very tiny droplets in the water); when the paint dries, the water evaporates, and the pigment and vehicle particles bind together, forming a strong film.

Varnish and Lacquer Varnishes are produced by heating a drying oil, resin, drier, and solvent together. Applied as a thin film, varnish gives a hard transparent coating. The numerous kinds of varnish include so-called spirit varnish and asphalt varnish.

Lacquers are natural and synthetic varnishes, particularly those obtained from the sap of the varnish tree, Rhus verniciflua, a Japanese sumac. Lacquer is applied as a thin coating to wood, metal, or ceramic articles; when hard, the lacquer coat is polished smooth with an abrasive, and another coat is applied over it. More than 30 coats are often used on a fine piece of lacquerwork.

Pigment
A substance that imparts color to other materials. Most paint pigments are metallic compounds, but organic compounds are also used. Some metallic pigments occur naturally, e.g., the oxides that produce the brilliant coloring of rocks and soil in the W U.S. Plants and animals also contain pigments. Chlorophyll (green) and carotene (yellow) produce bright colors in plants. Blood receives its red color from hemoglobin, and various pigments color human skin.