Nonuniform carbohydrate degradation during pulping can be more harmful to pulp strength than the same degree of degradation occurring uniformly. A modified G-factor model that incorporates the history of both temperature and [OH-] changes in wood chips during cooking is presented. This method requires knowing the variation in [OH-] across the thickness of the wood chip and during the cooking. These variations can be determined by numerically solving a set of mass-transfer equations with kinetic reaction terms using a computer program. The G-factor values are then converted to pulp viscosity. The model was experimentally validated by measuring the viscosity profiles over the thickness direction of hand-cut wood chips. Both measured and calculated profiles showed that the viscosity of the cellulose at the chip center was 50-100% higher than that at the edge of the 10-mm-thick chips. The difference in these viscosities for a S-mm-thick chip was only 10-15%.