Abstract: High pore volume silica materials are useful as thickening, reinforcing and flatting agents. This invention comprises selectively forming silica gels having pore volumes in the range of 1.2 to 3.0 cc/g. These high pore volume silica gels can be produced by the alkaline gelation of a mixture of silicate and ammonium hydroxide at a pH of from 10.6 to 11.2, using a water soluble silica desolubilizing agent selected from the group consisting of ammonia, monohydric alcohols, glycols, ketones and salts. The silica is then aged, neutralized, optionally aged a second time, filtered and washed. This silica may then be dried and directly used, or it may be milled to a smaller size. For use as a thickening agent, the silica is milled in a fluid energy mill to an average particle size of less than about 1 micron, and preferably to less than 0.5 micron.