White lead, a whitish corrosion product of lead, was formerly used to provide opacity in paints, especially in house paints. The white pigment in a colored paint is often called the hiding pigment. In addition to preventing the sun's damaging rays from affecting the surface beneath the paint, the white lead also POISONOUS!helped prevent the growth of mold and mildew. Not until early in the 20th century was a successful substitute, titanium dioxide (TiO2), patented, and even then, it did not come into prevalent use by itself until the middle of the 20th century. Earlier in the century, titanium oxide and white lead were often mixed.Also see zinc white.