The colors of textile products, or in other words, the colors of dyed or printed fabrics which will be in contact with the human body as clothing, must be resistant to sweat. Sweat fastness is made to determine this property of fabrics. In fact, the method of determining perspiration fastness is similar to the methods of determining color fastness to water fastness or sea water fastness. However, the solution used is different. Alkaline solution or acidic solution is used for sweat fastness measurements.

The purpose of sweat fastness is to determine whether the fabrics woven with dyed yarn undergo a color change with the sweat and temperature found in the human body when they are subsequently used as clothing. In general, the dark shades of dyed yarns are applied to the sweat and temperature conditions of the human body in the authorized laboratories and it is monitored whether there is any staining on the fabric.

The contamination of the dyed yarn on the fabric is determined by gray scale after the applied process (TS 423-3 EN 20105-A03 Textile - Methods for determination of color fastness - Section A03: Using gray scale for the evaluation of color flow). If the fastness value is higher than 4, the fabric is considered clean, otherwise the goods will be washed again. The size of the stain is directly the expression of the fastness value. Evaluation is performed using D65 daylight in the light cabinet.

The fastness of sweat in textile products with the aim of detecting the color changes that may occur with the sweating of human body and polluting other products in this way is determined in accordance with the following standard:

• TS EN ISO 105-E04 Textiles - Color fastness tests - Part E04: Color fastness to sweat

The determination of sweat fastness must be carried out in laboratories accredited by national or international accreditation bodies in accordance with the standards of TS EN ISO / IEC 17025 General Conditions for the Competence of Testing and Calibration Laboratories.