In the textile industry, the resistance of the dyestuffs on textile materials to various factors encountered during production and usage stages is called fastness. As can be understood from this definition, fastnesses vary according to the properties of the textile material to which the dyes are applied and different factors such as light, sweat and water. Some fastness of textile products can be high, some fastness can be low. For example, some textile products may have a low fastness to washing and a high fastness to dry cleaning. This may depend on the dyestuffs used in the textile product, the dyeing methods or the type of fibers.

Essentially, the fastness of a textile product depends on the following factors:

• Properties of dyes used
• Selection of dyestuffs suitable for textile products
• Type and number of bonds between fibers and dyestuff molecules
• After the dyeing and printing process, the finishing works of the iron are done correctly and adequately

The fastness of textile products is an important feature in terms of showing the quality of the products.

There are a wide range of fastnesses and these are generally divided into two groups: fastnesses during production and fastnesses during use.

During the production and use of the products, fastness tests are carried out for textile products. These test results determine the quality of the products and at the same time show the strength of the products against external factors. In addition, fastness tests are carried out to determine the usage and maintenance properties of textile products.

Accompanying fabrics of different materials are used to determine the fastness tests of colored product samples against other materials in the same environment. During testing, these accompanying fabrics are sewn into the sample of the product to be tested. These fabrics are woven from yarns such as cotton, wool, linen, viscose, acrylic, polyester or polyamide, and are of densities and weights determined by the relevant standards.

Scales were established in order to provide an assessment standard for fastness tests performed by laboratories accredited in accordance with the standards of TS EN ISO / IEC 17025 General Conditions for the Competence of Testing and Calibration Laboratories. These scales are divided into two groups as gray scale and blue scale and are determined by the following standards.

• Gray scale used for fading assessment: TS 423-2 EN 20105-A02 Textiles - Methods for determining color fastness - Part A02 - Using gray scale for assessment of fading
• Gray scale used in staining assessment: TS 423-3 EN 20105-A03 Textile - Methods for the determination of color fastness - Part A03: Using gray scale for the assessment of color flow
• Blue scale used to assess light fastness

The blue scale is used to assess the light fastness of textile products. The gray scale is used in all other fastness assessments except light fastness.

Fastness to use refers to the resistance of the textile product to the effects it will be exposed to during use. The aesthetics, appearance and taste suitability of the products are effective on the sale of that product. For this reason, fastness checks to be performed is an important study that determines the product quality. The main fastnesses of use are sweat, water, dry cleaning, ironing, light, rubbing, washing and shrinkage fastness.

The main fastness tests performed in accredited laboratories are:

• Wash fastness
• Washing fastness with oxidative bleach
• Dry cleaning fastness
• Sweat fastness
• Water fastness
• Water dripping fastness
• Rubbing fastness
• Light fastness
• Light fastness in weather conditions
• Solvent fastness
• Sweaty light fastness
• Chlorine fastness fastness
• Chlorine-free bleaching fastness
• Fastness to sea water
• Pool water fastness
• Dry heat fastness
• Hot press fastness
• Burnt gas smoke fastness
• Frosting fastness
• Fastness to saliva
• Phenolic yellowing fastness
• Fastness of dye transfer in storage
• Fastness to rust resistance
• PVC fastness
• Ozone fastness
• Color fastness to dye transfer
• Alkaline dripping fastness
• Acid dropping fastness
• Color fastness to steam