Perspiration Colorfastness Testing

Colour fastness to perspiration testing mainly conducts scientific testing and analysis on the colour fastness to perspiration testing items, colour fastness to acid perspiration testing, colour fastness to alkaline perspiration testing, colour change fastness evaluation, staining fastness evaluation and combined perspiration testing, objectively assessing the product quality grade and issuing a detailed test report, providing a basis for manufacturers' quality control and downstream users' product acceptance.

Testing Items

Colour fastness to perspiration testing items: The colour fastness to perspiration is a testing item for evaluating the ability of the textile to maintain its original colour after the action of the artificial perspiration under the specified conditions. It is directly related to the risk of the dye fading or transferring to the skin or the other fabrics caused by the human perspiration infiltration during the wearing process of the textile, especially the underwear. It is an important indicator for measuring the wearing performance and safety of the textile.

Colour fastness to acid perspiration testing: This item simulates the slightly acidic perspiration environment secreted by the human body after the normal or strenuous activities. The testing uses the artificial acid perspiration prepared according to the standard formula (usually with the pH value of about 5.5), evaluating the colour change (staining) of the fabric under this condition and the possible staining onto the other fabrics. It is the key for measuring the quality of the summer or sports textiles.

Colour fastness to alkaline perspiration testing: This item simulates the alkaline perspiration environment secreted by the human body under the specific physiological states. The testing uses the artificial alkaline perspiration (usually with the pH value of about 8.0). Since the alkaline environment may be easier to destroy some dye structures, the assessment of some dyes (such as the reactive dyes) is particularly strict. It is the necessary part of the comprehensive colour fastness evaluation of the textile.

Colour change fastness evaluation: Refers to the degree of the colour change of the tested sample itself before and after the perspiration action. The evaluation personnel or colour measuring instruments compare the tested specimen with the original sample under the standard light source, and rate the grade according to the grey scale or colorimeter data. The higher the grade (such as grades 4-5), the slighter the colour change and the better the colour fastness.

Staining fastness evaluation: Refers to the degree of the colour transfer caused by the dye on the tested sample to the adjacent multi-fibre adjacent fabric or single-fibre adjacent fabric under the perspiration action. By rating the staining grade of the adjacent fabric (also using the grey scale), it can be judged whether the dye will contaminate the skin or the other clothing, directly related to the consumer use experience and health safety.

Combined perspiration testing: To comprehensively evaluate the product performance, some standards or customer requirements will carry out the "acid/alkaline perspiration combined testing". That is, the same sample needs to undergo the testing with both the acid and alkaline perspirations successively or simultaneously, to simulate the more complex actual use scenarios, putting forward the higher requirements for the dye selection and process of the textile.

Testing Scope

Various textile and garment products: This is the most important application field of the colour fastness to perspiration testing, covering all the textiles that may contact the skin. Including but not limited to the underwear, T-shirts, shirts, sportswear, swimwear, socks, towels and bedding (especially the bed sheets, quilt covers and pillowcases). It is one of the assessment items of the mandatory national standard GB 18401 "National general safety technical code for textile products".

Special functional textiles: For the textiles with the special functions such as the moisture absorption and sweat wicking, antibacterial and sun protection, the colour fastness to perspiration testing is particularly important. Because the perspiration components may have the complex reactions with the functional auxiliaries or dyes, the testing can verify the function persistence and safety in the perspiration environment, avoiding the function failure or the generation of the hazardous substances.

Decorative textiles: Such as the sofa covers, automotive seat fabrics and curtains. Although they do not directly contact the body, under the specific environments (such as the high temperature and high humidity car interiors and the sunny windowsides), the human perspiration may indirectly contact them. The testing can evaluate the colour stability during use, ensuring the beauty and durability of the products.

Fabrics with the coating or printing: For the textiles processed by the coating, transfer printing or digital printing processes, the colour fastness to perspiration testing is an effective means to check the fastness of the printing or coating. It can evaluate whether the printing patterns blur, the coating falls off or sticks under the perspiration action.

Infant and children's textile products: Due to the delicate skin, active sweat glands of the infants and young children, and their habit of biting the clothing, the colour fastness to perspiration requirements of their products are usually higher than the adult products. The relevant standards (such as GB 31701) have the strict regulations on this, to prevent the dye shedding from being inhaled by the infants and young children or absorbed through the skin.

Export-oriented textiles: The requirements for the colour fastness to perspiration vary in the different international markets. For example, the European and American buyers usually require the simultaneous testing of the acid and alkaline perspirations, and designate the use of the ISO, AATCC or BS EN standards. Carrying out this testing is the necessary premise for meeting the customer requirements, breaking through the technical barriers to trade and obtaining the orders.

Testing Methods

International standard method (ISO 105-E04): This is a widely adopted test method internationally. Its core is to sew the specimen and the specified adjacent fabric to form a combined specimen, completely immerse it in the artificial perspiration, place it in a dedicated perspiration colour fastness tester, maintain it under the constant pressure (such as 12.5 kPa) and temperature (37±2 ℃) for a certain time (usually 4 hours), then dry it and rate the colour change and staining grades.

American standard method (AATCC 15): An American Association of Textile Chemists and Colorists standard. The principle is similar to the ISO method, but there are differences in the perspiration formula, specimen dimensions, selection of the adjacent fabrics and the specific operation details. For example, the AATCC standard more commonly uses the multi-fibre adjacent fabrics (containing the strips of the various fibres), and the pH value control range of the perspiration may be slightly different.

Chinese national standard method (GB/T 3922): The Chinese national standard "Textiles — Tests for colour fastness — Colour fastness to perspiration" modifies and adopts the ISO 105-E04. This method specifies in detail the preparation formulas of the two artificial perspirations of the acid (pH=5.5) and alkaline (pH=8.0), test equipment, operation steps and rating methods, and is the main basis for the domestic arbitration and product quality inspection.

Key steps of the perspiration preparation: The accurate preparation of the artificial perspiration is the basis of the reliability of the test results. The analytically pure grade chemicals (L-histidine monohydrochloride monohydrate, sodium chloride, disodium hydrogen phosphate, etc.) and grade 3 water need to be used, strictly prepared according to the molar concentrations and sequences in the standards, and precisely adjusted to the specified pH value with a pH meter. It should be prepared immediately before use or stored under the specified conditions.

Specimen preparation and combination: The specimen needs to be representative, avoiding the selvedge. Usually, a specimen of 40 mm × 100 mm is cut, and is attached face-to-face with the multi-fibre adjacent fabric of the same size or two single-fibre adjacent fabrics (one of the same fibre as the specimen, and one of the specified standard fabric), sewn along one short side to form a combined specimen.

Test process control: The combined specimen needs to be fully immersed in the perspiration (the liquor ratio is usually 50:1), ensuring the air bubbles are excluded. When placed in the tester, a glass plate or acrylic resin plate needs to be covered on the specimen to apply the uniform pressure. The whole testing process should be carried out in a constant temperature incubator to ensure that the ambient temperature is stable at about 37 ℃.

Testing Standards

Domestic Standards:

1. GB/T 3922-2013, Textiles — Tests for colour fastness — Colour fastness to perspiration

2. GB/T 250, Textiles — Tests for colour fastness — Grey scale for assessing change in colour

3. GB/T 251, Textiles — Tests for colour fastness — Grey scale for assessing staining

4. GB 18401-2010, National general safety technical code for textile products

International Standards:

1. ISO 105-E04, Textiles — Tests for colour fastness — Part E04: Colour fastness to perspiration

2. ISO 105-A02, Textiles — Tests for colour fastness — Part A02: Grey scale for assessing change in colour

3. ISO 105-A03, Textiles — Tests for colour fastness — Part A03: Grey scale for assessing staining

4. AATCC 15, Colorfastness to perspiration

Note: The applicable standard can be selected according to the product use and customer trade requirements; standards agreed in the contract take precedence over general standards.

Testing Instruments and Equipment

Perspiration colour fastness tester (Perspirometer): The core equipment, used to apply the constant and uniform pressure to the combined specimens immersed in the perspiration during the testing. It is usually composed of a group of parallel placed steel plates and spring or weight pressing devices, ensuring that each specimen bears the same pressure (such as 12.5 kPa). The instrument material needs to be corrosion-resistant to ensure the stability of the long-term use.

Constant temperature incubator/oven: Used to provide and maintain the constant temperature environment required for the testing (usually 37±2 ℃). It is required that the temperature uniformity in the chamber is good and the fluctuation is small, to ensure that all the specimens react under the same temperature conditions, guaranteeing the comparability and repeatability of the test results.

Laboratory pH meter: Used to precisely measure and adjust the pH value of the artificial perspiration, and is the key instrument for ensuring that the test conditions meet the standard requirements. It needs to be regularly calibrated with the standard buffer solutions, with the good electrode condition, and the measurement precision usually requires reaching ±0.02 pH units.

Standard light source colour matching cabinet: Used for the colour change and staining rating of the specimen before and after the testing. It provides the standard lighting conditions such as the D65 daylight light source, eliminating the interference of the ambient light on the colour judgement, ensuring that the rating personnel can carry out the visual comparison under the consistent and neutral light, improving the consistency and objectivity of the rating results.

Electronic balance: Used to precisely weigh the various chemical reagents required for preparing the artificial perspiration. It requires the high precision (at least 0.001 g), to ensure the accuracy of the perspiration component concentrations, which is the basis for reproducing the simulation of the real human perspiration chemical composition.

Standard adjacent fabrics: Including the multi-fibre adjacent fabrics (such as the DW type, containing the six fibre strips of the acetate, cotton, polyamide, polyester, acrylic and wool) and the single-fibre adjacent fabrics (such as the cotton, wool, silk and polyamide). These adjacent fabrics need to meet the standard requirements, with the uniform staining characteristics, and are the benchmark materials for evaluating the staining degree.

Rating auxiliary tools: Mainly including the grey scale for assessing change in colour (ISO 105-A02 / GB/T 250) and the grey scale for assessing staining (ISO 105-A03 / GB/T 251). The scales are composed of a series of neutral grey colour chips, representing the colour differences of the different grades, and are the direct comparison basis of the visual rating.