Abstract: The invention concerns a method for conditioning in a thermosetting resin a quantity of waste stored in water.According to the invention, a liquid hardening agent, immiscible with water and having a density greater than that of the water, is used in order to harden the resin; this hardening agent is then mixed with the waste stored in the water and then the waste is left to decant in the hardening agent; then the water present above the decanted waste transferred into the liquid hardening agent is extracted and the waste transferred into the liquid hardening agent is mixed with the epoxy resin so as to obtain a solid block.In particular, the waste may be ion exchanger resins. Adding of the hardening agent to the waste stored in the water makes it possible to limit a temperature rise during hardining and to obtain solid products having an improved density.