AbstractManganese in the pulp during the bleaching process has a marked effect in reducing the reflectance of the pulp. This effect is most notable in the chlorine dioxide bleaching stage. The effect is variable depending on the stage and solubility of the manganese contamination, the final pH of thc pulp, the filter water used in washing the pulp and other unknown and variable factors. The manganese contamination of unbleached pulp is largely removed in the chlorination stage, but subsequent contamination is more difficult to remove although a final acid wash does improve the reflectance.