The invention relates to agents that are used to improve optical properties such as opacity and/or brightness of dry products based on mineral matter containing said agents. More specifically, the invention relates to a method of producing dry products based on mineral matter, in which the agents used to improve the opacity and/or brightness of said dry products take the form of controlled-structure water-soluble polymers which are obtained using a controlled radical polymerisation method employing a particular alkoxyamine as a polymerisation initiator. The invention also relates to the use of aqueous suspensions and/or dispersions of mineral matter containing said polymers for the same purpose. The aforementioned dry products comprise plastics, filled paper, dry films produced by drying a coating slip, dry films produced by drying an aqueous paint formulation or dry films produced by drying an aqueous cosmetic formulation, which contain mineral matter as well as said polymers.