Abstract: The invention relates to a process for degreasing and cleaning metal surfaces with surfactant containing aqueous cleaning liquids in baths and/or by spraying. In order to obtain an exact measurement of the bath load and cleaning reserve economically and quickly to allow more accurate subsequent metering of the cleaning agent, the invention provides that, as a measure of the current reserve of cleaning liquid, a bubble tensiometer is used to measure a value correlated with the dynamic surface tension and operated with a sufficiently constant gas flow, the measurements are compared with a predetermined set value obtained for the cleaning agent used by calibration, and, depending on the results of comparison, appropriate steps are taken to treat the cleaning liquid.