Wool Fabric Inspection

Wool fabric inspection mainly conducts scientific testing and analysis on fibre composition and content, colour fastness testing, physical and mechanical properties, dimensional stability, pilling performance and pH value determination, 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

Fibre composition and content: In accordance with the relevant standards (such as GB/T 2910 and ISO 1833), quantitative chemical analysis is carried out on the wool fibre content in the wool fabric, accurately determining the blending ratio of the wool and other fibres (such as polyester fibre, nylon and cotton), ensuring consistency with the product claims, and preventing the adulteration of inferior products or false labelling.

Colour fastness testing: Comprehensively evaluates the colour retention ability of the wool fabric during use or processing, mainly including the colour fastness to rubbing (dry rubbing and wet rubbing), colour fastness to perspiration (acid and alkali), colour fastness to washing and colour fastness to light. These items are directly related to the appearance durability and safety of the finished garments after wearing, washing and sunlight exposure.

Physical and mechanical properties: Tests the basic properties of the fabric under force, including the breaking strength and elongation at break, tearing strength and bursting strength. These indicators reflect the durability and wearability of the fabric, and are particularly important for wool products such as coats and suits that need a certain shape retention.

Dimensional stability: Mainly tests the dimensional change rate (shrinkage) of the wool fabric after washing, including the relaxation shrinkage and felting shrinkage. Since the scale structure of the wool fibre is prone to felting shrinkage, this test is the key item for evaluating the quality of wool fabrics, especially washable products.

Pilling performance: Simulates the degree of pilling formed on the surface of the wool fabric due to friction during wearing. After testing with equipment such as the Martindale pilling tester or the random tumble pilling box, the rating is carried out by comparison with the standard photos. The higher the grade, the better the anti-pilling performance of the fabric.

pH value determination: Detects the acidity and alkalinity of the aqueous extract of the wool fabric. The residual strong acid or strong alkali will not only damage the wool fibres, affecting the handle and strength of the fabric, but may also irritate the human skin. The standards usually require that the pH value of textiles (especially those in direct contact with the skin) is in the range from weakly acidic to neutral.

Formaldehyde content: Detects the content of free and partially hydrolysed formaldehyde in the wool fabric. Formaldehyde is commonly used for the anti-wrinkle and anti-shrinkage finishing of textiles, but an excessive residue will harm human health. The report needs to clarify whether its content meets the limit requirements of the national mandatory standards (such as GB 18401).

Testing Scope

Worsted wool fabrics: The testing objects are mainly high-count and light-thin fabrics woven with worsted wool yarns, such as serge, gabardine and valitin. The testing focus is on their fineness, smoothness, strength, colour fastness and excellent dimensional stability, to meet the demanding quality requirements of high-grade suits and formal wear.

Woollen wool fabrics: The testing objects are rich and thick fabrics woven with woollen yarns, such as melton, flannel and tweed. Testing focuses more on the fullness, elasticity, warmth retention, anti-pilling performance of the fabric, and the special bulkiness and style retention evaluation unique to thick fabrics.

Wool blended fabrics: The testing objects are fabrics blended or interwoven with wool and other fibres (chemical fibres, silk and cotton). In addition to the conventional items, the blending ratio needs to be precisely analysed, and the comprehensive performance under the synergistic effect of different fibres needs to be evaluated, such as the improvement of the strength and wrinkle resistance by the addition of polyester.

Wool knitted fabrics: The testing objects are the materials of wool sweaters and wool underwear woven by the knitting process. The testing items need to consider the characteristics of knitted fabrics, such as the bursting strength, stitch density, extensibility and recovery, and snagging resistance, and pay attention to their shape retention ability after washing.

Fabrics with special finishing: The testing objects are wool fabrics finished with functions such as shrink resistance (machine washable), moth proofing, antistatic and waterproof and oil repellency. The testing scope needs to be extended to the effectiveness and durability verification of the corresponding functions, while evaluating the influence of the finishing process on the original handle, style and ecological safety of the wool.

Fabrics at different processing stages: The testing scope covers the whole process from the wool top, yarn to the grey fabric and the finished fabric after dyeing. The testing focus of different stages is different. For example, the grey fabric stage focuses on the physical properties and potential defects, while the finished fabric stage comprehensively examines the appearance, colour fastness and chemical safety.

Testing Methods

Chemical analysis method (composition quantification): Mainly in accordance with the ISO 1833 or GB/T 2910 standard series, using the difference in the solubility of different fibres in specific chemical solvents for separation and quantification. For example, the sodium hypochlorite method is used to dissolve the wool, and the remaining part is the other non-protein fibres, thereby calculating the precise wool content.

Instrumental physical test method: A standardized electronic strength tester (such as INSTRON) is used to determine the breaking strength and tearing strength; a Martindale abrasion and pilling tester is used to evaluate the pilling performance; and a shrinkage testing machine with a standard washing procedure is used to determine the dimensional change. All operations strictly follow the parameters such as the specimen size, gauge length and speed specified by the test standards.

Colour fastness rating method: The tested specimen is compared and rated with the standard grey scales or blue wool reference standards. A rubbing fastness tester is used for the colour fastness to rubbing, a standard soaping machine for the colour fastness to washing, and a xenon lamp aging test chamber for the colour fastness to light. The rating is completed by trained raters under a standard light source cabinet (such as the D65 light source).

Ecological safety test method: For the formaldehyde content, the water extraction method is usually adopted, and after colour development with acetylacetone, the determination is carried out with a spectrophotometer; for the pH value, the water extraction-electrode method is adopted, directly reading with a calibrated pH meter. For the detection of hazardous substances (such as decomposable aromatic amine dyes and heavy metals), precision instruments such as gas chromatography-mass spectrometry (GC-MS) and atomic absorption spectrometry (AAS) need to be used.

Appearance inspection and style evaluation: Under standard lighting conditions (such as north-facing natural light or equivalent artificial light sources), the inspectors carry out subjective inspection and recording of the defects of the fabric (such as thick and thin places, yarn faults, weaving faults and dye stains), lustre, handle and pattern definition, and combine the comparison and assessment with the standard photos or physical reference samples.

Functional test method: The moth proofing test is evaluated through a specific insect damage experiment; the waterproofness is tested by the hydrostatic pressure test or the spray test; and the antistatic property is evaluated by determining the surface resistance or the charge half-life of the fabric. These methods all need to simulate the actual use environment or set accelerated experimental conditions.

Testing Standards

Domestic Standards:

1. GB/T 2910, Textiles — Quantitative chemical analysis

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

3. GB/T 3920-2024, Textiles — Tests for colour fastness — Colour fastness to rubbing

4. GB/T 3921-2008, Textiles — Tests for colour fastness — Colour fastness to washing with soap or soap and soda

International Standards:

1. ISO 1833, Textiles — Quantitative chemical analysis

2. ISO 13934-1, Textiles — Tensile properties of fabrics — Part 1: Determination of maximum force and elongation at maximum force using the strip method

3. ISO 105, Textiles — Tests for colour fastness

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

Electronic fabric strength tester: Used to precisely measure the mechanical properties of the fabric such as the breaking strength, elongation at break and tearing strength. The equipment is equipped with pneumatic or mechanical grips, can set a constant tensile speed, and the computer system automatically records the force-displacement curve and calculates the results, ensuring objective and accurate data.

Martindale abrasion and pilling tester: Simulates the situation of the fabric being subjected to continuous and multi-directional friction in daily wearing. Under a specified pressure, the fabric specimen and the standard abrasive carry out relative motion in a Lissajous trajectory. After a predetermined number of frictions, its wear or pilling grade is evaluated. It is the key equipment for evaluating the durability of wool fabrics.

Standard light source colour matching cabinet: Provides multiple standard light sources such as D65 daylight, TL84 shop light and UV ultraviolet light, providing a stable, uniform and consistent lighting environment for the inspectors in the colour difference comparison, colour fastness rating and appearance defect inspection, avoiding the subjective judgement errors caused by the light source changes.

Xenon lamp weathering testing machine: Used to determine the colour fastness to light and weather resistance of wool fabrics. The equipment simulates the solar spectrum through a filter system, and can control the temperature and humidity, accelerating the photoaging process of the fabric. The colour fastness to light grade is determined by comparing the fading degree of the specimen with the blue wool reference standards.

Shrinkage testing machine and oven: Usually composed of a pretreatment washing machine (which can simulate hand washing or machine washing), a tumble dryer or flat press machine, and a standard oven. After the specimen is washed and dried according to the standard procedure, the dimensional change rate in the warp and weft directions is precisely calculated by measuring the distance change of the marked points.

pH meter and spectrophotometer: The pH meter is used to determine the acidity and alkalinity of the aqueous extract of the fabric, and needs to be regularly calibrated with standard buffer solutions. The spectrophotometer is mainly used for the quantitative analysis of chemical substances such as formaldehyde, and the precise content is calculated by measuring the absorbance at a specific wavelength and comparing with the standard curve.

Fibre composition analysis system: Including a chemical fume hood, analytical balance, constant temperature water bath, vacuum filtration device and dryer. It is used for a series of operations such as the chemical dissolution, filtration, drying and weighing of the fibres, and is the essential infrastructure combination for completing the quantitative chemical analysis of the fibre composition.