Washing is a finishing process applied to fibres, yarns and fabrics.

Washing is normally carried out in hot water (40-100°C) in the presence of wetting agent and detergent. The detergent emulsifies the mineral oils and disperses the undissolved pigments. The choice of the surfactants may vary also depending on the type of fibre. Mixtures of anionic and non-ionic surfactants are commonly used. An important factor in the selection of a surfactant is its effectiveness in strong alkaline conditions.

Washing efflluents are mainly composed of soap, grease, synthetic detergents, detergents and a small amount of bacteria, coliform bacteria, viruses and other harmful substances, has become an important source of water pollution.

After washing effluents are discharged into natural water,dissolved oxygen is consumed and slightly toxic to aquatic organisms, which can cause fish malformation and eutrophication caused by phosphate solvent.