Sea Water Colorfastness Testing

Colour fastness to sea water testing mainly conducts scientific testing and analysis on the definition of the colour fastness to sea water, fading fastness assessment, staining fastness assessment, colour tone change evaluation, physical property correlation evaluation and post-test specimen condition recording, 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

Definition of the colour fastness to sea water: The colour fastness to sea water refers to the ability of the dyed or printed textile to resist the colour change (fading) and resist the staining of the adjacent fabric after immersion in sea water. This testing item simulates the colour stability of the textile (such as swimwear, sailing clothes and beach towels) in the sea water environment, and is an important indicator for evaluating its durability and quality.

Fading fastness assessment: Mainly evaluates the degree of colour change of the specimen itself after the action of sea water. The treated specimen is compared with the original sample under a standard light source, and the rating is carried out with the grey scales or instruments. The smaller the colour change and the higher the grade, the better the colour stability of the textile to sea water.

Staining fastness assessment: Evaluates the degree of colour staining caused by the specimen to the specified adjacent fabrics (such as cotton, wool and nylon) under the action of sea water. The treated adjacent fabric is compared and rated with the unstained original adjacent fabric. The lighter the staining and the higher the grade, the lower the transfer tendency of the dyes or finishing agents to other fabrics.

Colour tone change evaluation: In addition to the change in the colour depth, it is also necessary to observe whether the hue or chroma of the colour changes. Sometimes the components in the sea water may cause the hydrolysis or chemical reactions of the dyes, leading to the colour tone shift (such as turning red or yellow), which also belongs to the scope of the colour change.

Physical property correlation evaluation: Before and after the colour fastness testing, the changes of the other physical properties of the fabric are sometimes correlatively evaluated, such as the strength loss, dimensional change or handle change. The salt and alkaline environment in the sea water may have a synergistic effect with the dyes and fibres, affecting the overall performance.

Post-test specimen condition recording: The appearance condition of the specimen after the test is recorded in detail, including whether there are phenomena such as the dye dissolution, fibre damage, surface fuzzing or local colour unevenness. These records help to comprehensively analyse the causes of the unqualified colour fastness, and provide a basis for the process improvement.

Testing Scope

Textile and garment products: Mainly applicable to all the textile finished products that may contact sea water, including but not limited to swimwear, diving suits, beach pants, sailing clothes, sailcloth for sailboats and life jacket fabrics. These products have mandatory or high-grade requirements for the colour fastness to sea water.

Home textiles: Including beach towels, outdoor seat cushions, awnings and the curtains and bedding of seaside resort hotels. Although these products are not continuously immersed, they will frequently contact the air containing salt mist or the splashed sea water, and poor colour fastness will affect the aesthetics and service life.

Industrial textiles: Involving the textiles used in marine engineering and fishery, such as fishing nets, cables, offshore aquaculture cages and marine interior decorative fabrics. These materials are exposed to the harsh marine environment for a long time, and require an extremely high colour fastness to ensure the label definition and structural safety.

Dyed yarns and fabrics: As the semi-finished products, the dyed yarns, woven fabrics and knitted fabrics also need to undergo the colour fastness to sea water testing, to control the quality of the finished products from the source. This helps the printing and dyeing enterprises to optimize the dye selection and dyeing processes.

Products of various dyeing processes: Regardless of the dyeing process adopted (such as exhaust dyeing, pad dyeing and printing) or the dye used (such as reactive dyes, disperse dyes and acid dyes), as long as the final product may contact sea water, it should be included in the testing scope.

Textiles with special finishing agents: For the textiles finished with the waterproof, UV resistant and flame retardant functions, the interaction between the finishing agents and the dyes in the sea water environment needs to be evaluated, and whether it will cause the colour fastness to decrease or produce new colour changes.

Testing Methods

Standard test method (ISO 105-E02): The general method formulated by the International Organization for Standardization. The textile specimen is sewn with the specified adjacent fabric, immersed in a simulated sea water test solution (sodium chloride solution), treated at a specific temperature and time, then dried, and finally the change in colour and staining grades are rated. This is the most basic and widely adopted method.

Simulated pressurized immersion method: To simulate the deep-sea or high-water-pressure environment (such as diving suits), a pressure control device can be added to the colour fastness to sea water tester. The immersion test is carried out under a certain sea water pressure, which can more truly reflect the colour fastness performance under the extreme use conditions.

Alternate immersion-drying method: Simulates the use scenario of the tide or the intermittent contact with sea water. The specimen is immersed in the simulated sea water according to the procedure, then taken out and dried under the specific conditions, and this cycle is repeated for multiple times. This method is more stringent for evaluating the fatigue resistance of the dyes and fibres.

Chlorinated sea water simulation test method: Considering that the sea water in some sea areas or the swimming pool water may contain residual chlorine, in addition to the sodium chloride, substances such as sodium hypochlorite are also added to the test solution, to evaluate the colour fastness under the combined action of "chlorine-salt". This method is particularly important for the products such as swimwear.

Actual sea water immersion comparison method: In addition to the laboratory standard testing, the specimen can be placed in a real sea water environment for a long-term hanging sample test. This method has a long cycle and many environmental variables, but the results are closest to the actual use situation, and is often used as a supplementary means for the scientific research and the verification of high-end products.

Rapid screening method: Used for the quality control in the production process, such as using a salt solution of a higher concentration or shortening the test time at a slightly higher temperature. However, the results of this method are only for the internal reference, and the final judgement still needs to be based on the standard method.

Testing Standards

Domestic Standards:

1. GB/T 5714-2019, Textiles — Tests for colour fastness — Colour fastness to sea water

International Standards:

1. ISO 105-E02, Textiles — Tests for colour fastness — Part E02: Colour fastness to sea water

2. AATCC TM 106, Colorfastness to Water: Sea

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 fastness tester: This instrument is the core equipment for carrying out the standard colour fastness to sea water testing. Through the equipped spring pressure plates and weights, a constant and uniform pressure is provided for the immersed specimen combination, ensuring the close contact between the specimen and the adjacent fabric, simulating the staining condition in the real wet fitting state.

Constant temperature oven: Used for the drying process of the specimen after the testing. It needs to precisely control the temperature (usually 60±2 ℃), ensuring that all the specimens are dried under the same conditions, avoiding the colour difference or result deviation caused by the uneven drying temperature.

Standard light source cabinet: The key equipment for rating the change in colour and staining grades. It provides multiple standard light sources such as the D65 daylight, UV light and cool white fluorescent light, ensuring that the raters carry out the visual comparison under unified and stable lighting conditions, eliminating the rating errors caused by different light sources.

Electronic balance and solution preparation utensils: Used to precisely prepare the simulated sea water test solution (such as 30 g of sodium chloride per litre of distilled water). The accuracy of the electronic balance needs to reach 0.01 g, and it is used together with the measuring cylinders, beakers and other utensils, ensuring that the concentration of the test solution meets the standard requirements.

Grey scales and staining scales: The physical standard tools for rating the change in colour and staining respectively. The grey scale is used to compare the colour difference of the specimen before and after the treatment, and the staining scale is used to compare the degree of the staining of the adjacent fabric. The valid scales that meet the ISO 105-A02/A03 standards and are not faded must be used.

Colour measurement and matching instrument: As the objective supplement of the visual rating. By measuring the colourimetric values (such as L*, a*, b* and ΔE*) of the specimen before and after the testing, the colour difference is calculated, and it can be converted into the corresponding fastness grade according to the built-in program, improving the objectivity and traceability of the results.