Ultrasonic cleaning uses cavitation bubbles induced by high frequency pressure (sound) waves to agitate a liquid solution. The agitation produces large forces on contaminants adhering to substrates such as metals, plastics, glass, rubber, and ceramics. This action also penetrates into blind holes, cracks, and recesses. The intention is to thoroughly remove all traces of contamination tightly adhering to or embedded in solid surfaces. Water or solvents can be used, depending on the type of contamination and the workpiece. Contaminants can include dust, dirt, oil, pigments, rust, grease, algae, fungus, bacteria, limescale, polishing compounds, flux agents, fingerprints, soot wax and mould release agents, and biological soiling including blood.