To obtain washing solutions are used clay powders produced by various plants and local lump clays. By the cost of clay material spent on the preparation of 1 m³ of standard solution (with a conventional viscosity of 25 s), as a rule, the wrong conclusion is made about the economic efficiency of local lump clays. Approximate calculations have shown that the replacement of local clays and mixed-composition clay powders used by geological organizations with high-grade clay powders is quite expedient and economically justified.