The influence of the nature of the salt and the conditions under which the salt crystallizes in porous materials have been studied to determine the different types of damage that can be produced. This study used brick as the porous material and three of the most commonly occurring soluble salts-sodium chloride, sodium sulfate and magnesium sulfate-to produce the deterioration. For each salt, three different experimental conditions of humidity, temperature, and/or crystallizing time were used to allow for different crystal growth and different degrees of hydration in the case of those salts that can form hydrates. The results are explained as a function of the thermohygrometric conditions existing at thetime the crystallization takes place. See also 22-1140 for more information on use of salt crystallization test as accelerated aging test for brick.