A double-shaft mixer is a continuous-flow type that mixes, kneads and moistens the clay to optimize the blending and disintegrating effect. As such, its essential functions are to homogenize nonuniform raw material, mix different raw materials together, blend in additives, amendments and water, and open up surface-dry material. Consequently, double-shaft mixers can be incorporated at different points of the preparation process, depending on the immediate task, i.e., before, during and after comminution, as well as upstream or downstream of clay storage. For example, double-shaft mixers can be used for closely adjusting the moisture of a raw material heading for storage and for disintegrating surface-dry material on retrieval. In the feed section, additives and water can be blended in to give the material its desired properties. The mixing zone is quite long, so the material takes considerable time to pass through it, giving the numerous mixing knives ample time to optimize the material’s homogeneity.