Abstract: A method for determining an electrostatic force present in a flat object, includes: (a) positioning the object on a flat support; (b) providing a series of testing membranes which are substantially free of electrostatic charges and have different standarized weights; (c) placing on the surface of the object one of the testing membranes and turning the support to an inclined position relative to a horizontal plane; (d) repeating step (c) with the other ones of the testing membranes; (e) examining which one of the testing membranes slides relative to the object after the support is inclined, and determining the smallest weight among the standarized weights, that permits a sliding movement between the testing membranes and the object, and the largest weight among the standarized weights, that prevents the sliding movement; and (f) evaluating the electrostatic force as a function of the largest weight and the smallest weight. An apparatus for carrying out the process is also disclosed.