The dynamic model of soil sealing developed by Assouline and Mualem <1997> is applied to study the effect of the main variables affecting seal formation, namely, the rainfall characteristics, the flow conditions, and the soil properties. The model is further extended to provide for the first time a quantitative estimation of the effect of the soil and water chemical properties on infiltration during soil surface sealing. The predicted effects of the chemical conditions on infiltration seem to be in agreement with experimental observations. Also, the model is used to explain the wide variability in seal thickness, found in the literature, in terms of the resolution of the method applied to measure the soil bulk density. ¿ 2000 American Geophysical Union