Measurements of the fundamental ac-susceptibility provide a sensitive
tool to study the shielding behavior of ceramic high-T(c) superconduct
ing material. In this work, ac-susceptibility data for differently pre
pared YBaCuO-samples are presented. From the data, information can be
extracted about an effective grain size, which is not necessarily iden
tical to the optically determined particle size. It is demonstrated th
at the data allow an estimation of the bulk quality which depends stro
ngly on the preparation conditions.