Abstract: The method of the present invention is directed towards a method to increase the pulp yield of a lignocellulosic material, or increasing pulp bulk and/or pulp viscosity. This method comprises the following steps; preparing a lignocellulosic material, contacting the lignocellulosic material in a vessel with hot water or steam for a predetermined time, producing acetic acid from the reaction of the hot water or steam and the lignocellulosic material, lowering the pH to less than about 4, removing lignocellulosic material extracts including a large percentage of hemicellulose, acetic acid and metal ions, exposing contacted lignocellulosic material to pulping chemicals in a pulping reactor, forming a contacted lignocellulosic material pulp with a kappa number below about 19 after about 90 minutes of contact with the pulping chemicals, exposing the contacted lignocellulosic material pulp to whitening agents, and producing a whitened hot water contacted lignocellulosic material pulp.