A method for producing molded parts (16), a water-soluble casting mold (6) being produced in a first step using a layering method, in particular using a powder bed-based layering method. In a second step, the surface of the casting mold (6) is sealed with the aid of a material (9; 10). A casting of the molded part (16) is then formed by filling the casting mold (6) with a free-flowing, hardenable material (13), in particular a hydraulically setting material. After the casting has solidified, the casting mold (6) is dissolved with the aid of an aqueous solution (18), in particular a heated aqueous solution (18). The present application furthermore relates to a material system for producing a water-soluble casting mold (6), comprising at least one water-soluble material for building a casting mold (6) in a layering method, as well as comprising at least one material (9; 10) for sealing the surface of the casting mold (6).