A fast technique based on a version of the Archimedes principle to measure
densities of irregular solids is presented. With this system, developed to
study superplastic cavitation, the sensitivity of +/-1 x 10(-4) g for weigh
ing in air, remains for weighing under the water. In principle, the optical
methods used for evaluating cavitation during superplastic deformation can
be calibrated by using this technique.