Water without additives usually does not clean at all or only insufficiently. With the use of suitable cleaning preparations, on the one hand the surface tension of the water is reduced for an optimal ultrasonic cavitation effect and, on the other hand, the contamination is optimally removed with the specific ingredients. The suitable preparation depends on the contamination (e.g. oil, blood, soot, ink etc.) and the object (stainless steel, copper etc.). When reprocessing medical instruments, cleaning and disinfection preparations specially designed for ultrasound must be used.