The fundamental analysis of deposit characteristics requires the knowledge of a size key that is difficult to obtain in crossflow filtration, which is the geometric characterization of the deposit and most especially its thickness. The measurement in situ of this size with an optical captor which will not alter the characteristics of the deposit allows to have complete information on deposit characteristics. The effects of different operating parameters on permeability, resistance, porosity and compressibility are discussed and lead to that the initial layers of the deposit constitute the determining resistance. The deposit is not homogeneous and the compressibility coefficient depends on concentration.