The textile washing process consists basically of three stages: 1) removal of the soiling from the substrate, 2) suspension of the soiling in the washing bath, and 3) prevention of redeposition of the soiling on the substrate from which has just been removed. The soiling removed may be caught again on the substrate to a greater or lesser extent during the detergent process. This phenomenon constitutes the unwanted redeposition of that impurity on the substrate and polymers are added to prevent it. The redeposition of impurities must be prevented during the washing of synthetic fibres, such as polyester or acrylic, which have a compact crystalline structure. The purpose of this work is to ascertain the behavior of a polyethylene glycol polyester copolymer when used as a detergent additive to prevent redeposition of solid impurities during the washing of standard polyester and acrylic fabrics. That polymer was used in washing tests in the presence of an anionic surfactant sodium dodecylbenzenesulfonate (SDBS), and a non-ionic surfactant, fatty alcohol ethoxylate with 7 moles E.O., separately and in mixtures of both with varying proportions. The soiling applied was carbon black, as a solid impurity in washing. In order to explain the observed behavior, the electrical double layer of the fabrics was characterized, depending on the surfactants and the mixtures tested