Paint is a liquid composition that dries to an opaque film. It is composed of four basic types of ingredients: pigments, which are powders that give opacity and color; binders, which act like glue to hold the pigments together and cause the film to adhere to the surface being painted; liquids, which make the paint thin enough to spread on a surface, and additives, which perform special functions such as thickening, reducing mildew, and more.

Paints are generally classified as either solvent-borne or waterborne. Solvent-borne wall paints, such as oil paints, use a petroleum derivative (for example, mineral spirits) as the solvent. Waterborne paints use water.

Waterborne wall coatings prevailed from prehistoric cave paintings up to medieval wall paintings. Natural proteins were used as binders for the pigments. Tempera used egg whites as a binder; distemper, a similar waterborne paint, used animal glues from hides and hoofs. Whitewash used milk casein to bind lime (calcium hydroxide) onto Tom Sawyer's fictional fence. But all these exhibited poor washability and durability. Linseed-oil-bound pigments -- used by the ancient Egyptians, early Romans and renaissance artists such as daVinci and Michelangelo -- were more durable, but were scarce until the linen industry expanded to provide ample flax seed, from which linseed oil was pressed. Hardening of the soft linseed oil films by rosin and adding volatile turpentine from the naval stores industry enhanced varnishes for Stradivarius violins, fine furniture and wooden floors. Turpentine was the only historic volatile organic solvent to control paint viscosities until the coke and petroleum industries distilled various naphthas.

These separate crafts came together only in the 1930s, when brilliant exterior waterborne paints enhanced and survived the 1933 Century of Progress Exposition in Chicago and the 1939-40 World's Fair in New York City.

How Was Kem-Tone^� Paint Different?
Sherwin-Williams chemists used science to combine two chemical opposites--oil and water. Their chemical innovation was to emulsify, in an aqueous system, traditional solvent-borne binders with casein and other traditional paint ingredients. The binders were casein, linseed oil and, later, tall oil (obtained from wood pulp). This technique set a new standard for the improvement of water-based paints. Eventually, as the product evolved, newly developed synthetic binders replaced the ones used in the original Kem-Tone^� paint.

Solvent-borne paints generally contain mineral spirits to thin the paint and make it "brushable." In contrast, Kem-Tone^� paint could be diluted with water. The Kem-Tone^� paint formulation consisted of many different ingredients.

No Muss, No Fuss, No Bother
Kem-Tone^� paint, which augmented Sherwin-Williams' family of "Kem" (standing for chemically evolved material) products, was the first multi-million-gallon, commercially accepted interior wall paint emulsified in water. The flat, interior finish covered with only a single coat, dried in one hour, had greatly reduced paint odor, and could be washed without removing the color. After painting, cleanup was easily accomplished with soap and water. These benefits were summarized in the advertising slogan, "No Muss, No Fuss, No Bother."

Kem-Tone^� paint's ease of application was enhanced by the introduction of the Roller-Koater™ paint roller. Inexperienced painters found that the applicator was faster to use than brushes and provided more even coverage. This made it easier for homeowners to become do-it-yourself painters -- an attractive alternative during the labor shortages of World War II.

Kem-Tone^� paint had another great advantage. It completely covered wallpaper, plaster, and painted walls, without requiring messy primers, sealers or thinners. Soon Kem-Tone^� and other waterborne paints supplanted wallpaper as the decorative wall finish of choice in the United States.

Future Inventions
The introduction of Kem-Tone^� paint in 1941 was the milestone that showed the viability of durable, washable water-based paint and led the way for future improvements. For example, after World War II, the Dow Chemical Company searched for ways to use its styrene-butadiene polymer (40 parts styrene, 60 parts butadiene), which it had developed for tires during the war. The search led Dow to develop styrene-butadiene latex (60 parts styrene, 40 parts butadiene) as a binder in water-borne paints.

Dow's binder helped to create a new Sherwin-Williams product: latex paint. In the late 1940s, the company introduced Super Kem-Tone^� paint, which used styrene-butadiene latex as the principal, but not sole, binder. This significantly improved the adhesion and durability of waterborne paints.

Since the 1940s, paints emulsified in water have passed through several additional phases. Styrene-butadiene latex paints yielded to new improvements, such as vinyl acrylic and acrylic latex binders for water-based paints.