The interaction forces between surfaces of cellulose, hemicellulose and mineral filler were directly measured for the first time using the surface force technique of Israelachvili and co-workers (Israelachvili, Adams 1978). A spin-coating technique was developed to prepare thin films (30-40 nm) of cellulose on the mica substrates employed in the surface force apparatus. The cellulose layers have a molecular scale roughness and, when immersed in water, swell considerably. The measured force vs. distance profile is characterized by three distinct regimes and is interpreted in terms of a simple model for the cellulose-water interface, namely, the water-swollen cellulose layer has long (and weakly) charged cellulose chains or "molecular fibrils" extending about 100 nm from its surface. Conventional DLVO theory cannot explain the forces observed between cellulose surfaces. Steric forces rather than electrostatic forces dominate the interactions due to the dangling tails of cellulose chains and the compressibility of the cellulose layer. Surface force measurements were also performed on adsorbed xylan layers. Nonequilibrium layers, whose structure and surface forces are dominated by the dangling tails of polysaccharide chains, adsorb via a "polymer reshuffling" mechanism consistent with the size (and charge) distribution for xylan molecules. In addition, the mechanism of calcium ion-induced aggregation of kaolin suspensions was investigated by studying the forces between model (mica) surfaces immersed in an aqueous sodium polyacrylate solution. An adhesive primary minimum, attributed to calcium ion-mediated electrostatic bridges, offers an explanation for the aggregates of face-to-face associated kaolin particles. The surface force technique clearly represents a novel approach for both applied and fundamental studies of the surface and colloid chemistry of papermaking and paper coating systems.