Plane supports based on clay are elaborate by using organic additives like agents of porosity. They are then characterized by various techniques: mercury porosimetry, nitrogen adsorption/desorption, electronic scan microscopy. According to the nature of clay, the nature of the organic additive and the technique of development used, the results are different. In this work, we present the evolution of the diameters of the pores and their distributions according to several experimental parameters. The whole of these results made it possible to direct materials thus obtained towards their applications in the water treatment by the membrane separation techniques. According to their diameters of the pores, they can be used either as membranes of microfiltration or like supports for membranes of ultrafiltration.