A method is provided for encapsulating products that can have lipophilic or hydrophilic, including volatile, properties in a polysiloxane membrane that is particularly impervious. A method is also provided for evaluating the imperviousness of capsules. The present method includes the following steps:a) formation of droplets by an emulsion between an oily phase containing the product to be encapsulated and an acidic aqueous phase heated to around 50° C. and in the presence of surfactants；b) addition and hydrolysis of at least one silane in order to obtain a silanol；c) increasing the pH in order to start condensation of the silanol to form a first membrane around the droplets of the product to be encapsulated；d) lowering the pH；e) increasing the pH, optionally preceded by adding a silane, in order to obtain a new condensation of silanol around the droplets of the product to be encapsulated.
