Differentiated Evaluation of Washing Performance in Washing Machines of Test Stain Strips as a Function of Temperature, Washing Duration and Load Size

Abstract Since the washing performance of household washing machines must comply with certain limit values, like the ecodesign requirements in Europe, the method of washing performance evaluation is crucial. Today, the washing performance is defined as an overall washing performance in IEC 60456:2010, constituting an calculation of the average sum of reflectance values of five different stain monitors. As a result, the different washing characteristics of each individual stain are totally neglected. This study investigates how the washing cycle affects the individual stains, when washing temperature, washing time and load size are varied systematically. The results show individual stains contribute differently to the overall washing performance. For a proper assessment of the washing performance, the individual stains’ contributions to the overall washing performance are required to be considered. A supplement of temperature sensitive stain monitors is suggested. E.g., as tea has a crucial contribution at higher temperature, this stain should have a higher influence in washing performance assessment when good bleaching or hygiene performance is requested.