Abstract: A method of improving opacity and brightness of paper containing synthetic sodium magnesium alumino silicate, sodium alumino silicate and silicic acid or silica pigments which utilizes reducing the structure of such pigments by hard media grinding.

Abstract: Novel alkali aluminum silicate particulates, modified with and containing a chemically bound alkaline earth metal, are disclosed. The alumino silicate pigments contain an alkaline earth metal, preferably calcium or magnesium, in addition to an alkali metal, such as sodium. In chemical composition, the pigments contain oxides of the alkaline earth metal, the alkali metal, aluminum and silicon and are distinguishable from co-precipitates. The pigments are prepared by introducing dilute solutions of an alkali silicate and an aluminum salt of a mineral acid into an agitated aqueous receiving medium containing an alkaline earth salt or hydroxide. The pH of the fluid reaction medium may be controlled to form finely divided precipitated particulates having improved properties and which may be used as pigments in paper, paint, rubber, inks, plastics, and the like.