Pigments give paints their color. There are two types of pigments: prime pigments and extender pigments. Prime pigments provide color and opacity, the ability to hide whatever the paint covers. Extender pigments provide bulk and other qualities for the paint.
Pigments come from organic and inorganic sources.
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Extender pigments can impact qualities such as gloss, washability, hiding ability, durability, and flow of the liquid. Clay from aluminum silicate is used to hide whatever it covers and is used as a flattening agent. Silica is used for exterior paints to provide dirt and stain resistance. Calcium carbonate is used to control gloss and mold. Talc as magnesium silicate is used to improve adhesion.
Binders are the adhesives that act like glue to hold the pigment particles together. They are the film-forming materials that are responsible for the adhesive qualities of paint. Binders, sometimes referred to as the vehicle, are different for latex and alkyd paints. Latex, or water-based binders, are synthetic solid polymers, such as acrylic or vinyl acrylic dissolved in water with soap. Solvent-based binders are synthetic polymers, such as alkyd, vegetable oil, or petroleum oil, dissolved in a chemical solvent. Chemical solvents are either hydrocarbons or oxygenated.
Solvents (meaning liquid) such as water or a chemical solvent, make the paint fluid enough to spread on a surface. Solvents help the coating to penetrate a surface and control the rate of drying. Solvents provide the desired viscosity for applying the pigment and binder to a surface. They evaporate as the paint dries.
Additives are for special performance functions. For example, a preservative may be added as a mildewcide, to reduce mildew problems for high-moisture areas. A biocide may be added to prevent bacterial growth in the can. A defoaming agent may be added to prevent foaming. Thickeners are used to reduce the drying time for application in hot weather. To comply with the VOC emissions laws, more solids are added, making paint heavier and slower to dry.