With wet bleaching, the cleansing effect is more effective and the consumption of bleaching earths can be reduced. The presence of water increases the cation exchange capacity of the bleaching earth, which improves hydration of the non-hydratable phosphatides. The best performance is observed for amount of water about 50–100% of amount of bleaching earth, which is not always economically acceptable. In wet bleaching, the oil and bleaching earth are contacted under atmospheric pressure for 20 minutes at about 70–90°C, which is followed by the usual bleaching process under vacuum for 15–30 min. During this step, the excess water evaporates allowing the bleaching earth to be filtered without problems.