PURPOSE: To reduce the cost of shaking out by immersing a precision casting to which refractories are stuck into a soln. contg. hydrofluoric acid, thereby removing the refractories.

CONSTITUTION: The soln. prepd. by adding nitric acid, etc., at 5W20wt.% or other ratios to the hydrofluoric acid is prepd. and the precision casting on which the refractories are stuck is immersed therein. The hydrofluoric acid generates pickling by forming pitting holes to the steel part of the precision casting and dissolves the casting mold at this time. An oxidation resistance suppressor such as nitric acid, however, suppresses the pickling. The drop of the casting mold refractories is extremely accelerated when the precision casting is oscillated. Since the need for using caustic soda which necessitates large electric power and much labor is thereby eliminated, the cost of the shaking out is reduced.