(57) A sheet which is a composite of (A) from about 1 percent to about 30 percent of a water-dispersible fiber such as wood fiber, (B) from about 2 percent to about 30 percent of a film-forming, water-insoluble organic polymer such as a copolymer of styrene and butadiene, and (C) from about 60 percent to about 95 percent of a finely-divided, substantially water-insoluble, non-fibrous, inorganic filler such as magnesium hydroxide is prepared by steps comprising:

(1) providing an aqueous dispersion of the fiber;

(11) mixing therewith (A) the inorganic filler and (B) the organic polymer in the form of an ionically stabilized latex;

(III) colloidally destabilizing the resulting mixture to form a fibrous agglomerate in aqueous suspension;

(IV) distributing and draining the aqueous dispersion on a porous substrate such as a wire to form a wet web; and

(V) drying the web.