A collecting electrode element for an electrostatic air cleaner with a reduced weight can be constructed with a lightweight conductive core sandwiched between particle collection layers which are supported and stabilized by a rigid frame. The conductive core may be conductive foil, conductive film, conductive ink, or conductive glue. The particle collecting layers may be flexible open-cell foam such as melamine which may be compressed between opposing frame elements. The frame may leave most and preferably at least 90% of the surface of the particle collecting layers exposed. The frame may have opposing frame elements secured to each other at a compressed area of the particle-collecting layers.