The current theory of crystal growth in pores has been further developed to include thermodynamics of real solutions for sodium sulfate and sodium chloride. This allows better quantification of the stresses developed by crystallization of these salts inside porous materials such as stone, brick or concrete. Results for sodium sulfate show that dissolution of its anhydrate produces supersaturations with respect to its decahydrate capable of generating tensile hoop stresses on the order of 10-20 MPa, largely in excess of the tensile strength of almost all stones. It also explains why, in the accelerated testing that involves cycles of impregnation and drying, all damage occurs during the impregnation and not the drying step. The situation in which crystallization is driven by evaporation is also discussed in light of understanding why sodium sulfate also induces more damage than sodium chloride during continuous capillary rise experiments. Results suggest that the classification of stone resistance to salt damage can change depending on the mode of supersaturation generation. (C) 2002 Elsevier Science B.V. All rights reserved.