Abstract: The cleaning apparatus includes a pre-rinse tank, a cleaning tank, and at least one post-rinse tank. The cleaning tank cleans oil, flux and other foreign matter off the surface of a work product by subjecting the work project to a rising stream of bubbles of uniform density which overflow the upper end of a chimney and return to the bottom end of the chimney. The bubbles are created by porous chambers internally pressurized with a gas such as air. The post-rinse tank is likewise constructed so as to subject the work product to a rising column of bubbles having uniform density across the width of the post-rinse tank but without any recirculation of the rinse liquid.