The textile washing process involves basically three stages: (1) removing the soiling from the substrate, (2) suspending the soling removed in the washing bath and (3) preventing redeposition of the soiling onto the substrate from which it has just been removed. In fact, soiling removed from the substrate may have deposited on it to a greater or lesser extent during the detergent process, as unwanted phenomenon that can be avoided using appropriate polymers. Preventing the redeposition of impurities is especially important during the washing of synthetic fibres with a compact crystal structure such as polyester or acrylics. The primary purpose of this work was to assess the performance of a polyethylene glycol polyester copolymer used as a detergent additive to prevent redeposition of solid impurities during the washing of standard polyester and acrylic fabrics in terms of the zeta potential of the fabrics. The copolymer was used in combination with the anionic surfactant, sodium dodecylbenzenesulfonate, the non-ionic surfactant fatty alcohol ethoxylate with 7 mol E.O. or both in variable proportions. The soiling used as a solid impurity in the washing process was carbon black. The observed behaviour is explained in terms of the electrical double layer of the fabrics, which was characterised separately with each surfactant and their mixture