White pigments are the major contributors in paint formulation.
White pigments are used not only in white paints, but also in
a substantial fraction of other pigmented paints to give lighter colors
than would be obtained using color pigments alone. All white pigments
are inorganic compounds of titanium, zinc, antimony, or lead.
pigment is essentially transparent tovisible light. Because of the difference inrefractive index between the pigment particlesand the vehicles, white pigments refract thelight from a multitude of surfaces and return asubstantial portion in the direction of illuminationwithout significant change in the spectralcomposition of the light.
The common white pigments are titaniumdioxide, derived from titanium ores; white lead,from corrosion of metallic lead; zinc oxide, fromburning of zinc metal; and lithopone, a mixtureof zinc sulfide and barium sulfate. Pure zinc sulfideand antimony oxide are less commonly used.Titanium dioxide may be crystallized in therutile or anatase form, depending on the methodof production. It may be further modified bysurface treatment to control the rate of chalkingand other properties. Rutile titanium dioxidehas a higher refractive index than anatase andtherefore higher hiding power, but it has asomewhat yellow color. Anatase titanium dioxideprovides a purer white.
White lead pigments are the oldest of whitepigments and were used extensively to provideexcellent hiding power, flexibility, and durabilityto interior and exterior paints and enamels.Consumer protection rulings have all butremoved white lead paints from the market,because leaded paint particles were ingested bychildren, with toxic effects.
