1. The freezing on method of preparation of zirconium boride sheaths is highly promising, and secures blank-shaping properties which are not exceeded by the properties of sheaths made by die extrusion. 2. The best processing characteristics are shown by fine zirconium boride powder slips with 8–10% paraffin wax and 1% of oleic acid, from which it is possible to produce blanks with a packing coefficient of more than 0.6, i.e., one which approaches the theoretical packing coefficient for spherical particles. 3. Mixtures with higher paraffin wax contents do not constitute fully structurized systems, and are subject to layering in the course of time, with the separation of pure paraffin wax on the surface. 4. Blanks frozen on from slips containing a substantial amount of unadsorbed paraffin wax have a low packing coefficient, and their paraffin wax content is higher than the mean paraffin wax content of the slip.