invention affords particular advantages in regard to the introduction and regeneration of the detergent or bleach in the wash liquor the introduction of the detergent or bleach is preferably controlled by a control system which compares the actual concentration determined with a pre set concentration the invention also enables the rinsing time to be shortened and the amount of rinsing water required to be reduced in another embodiment of the invention therefore rinsing is terminated when the actual concentration determined has fallen below a pre set concentration embodiments of the invention are described by way of example in the following with reference to the accompanying drawings wherein fig1 shows various sensor systems with which the process according to the invention may be carried out fig2 illustrates a batch washing machine with several measuring points for the measurement of concentration fig3 shows the dependence of the fluorescence intensity on the concentration of detergent fig4 shows the dependence of the fluorescence intensity on the concentration of an alkyl benzenesulfonate solution fluorescent ingredients already present in the detergent or bleach may be used for the fluorescence measurement however other fluorescent markers which are additionally added may also be used similarly where concentration is measured by determining the change in the state of polarization substances which bring about such a change for example sugar may be added to the detergent or.