Linen Cloth Testing

Linen cloth testing mainly conducts scientific testing and analysis on fibre composition and content, physical and mechanical properties, colour fastness, dimensional change rate, appearance quality and defects, and formaldehyde content and pH value, 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: This is the basic item of linen cloth testing, aiming to precisely identify the type of bast fibre in the fabric (such as flax, ramie and jute) and its percentage content in blended fabrics. It is determined by the chemical dissolution method or microscopic observation method, and the result directly affects the label marking compliance, pricing and performance expectations of the product.

Physical and mechanical properties: Evaluates the behavior of the linen cloth under load, mainly including the breaking strength, tearing strength and bursting strength. These indicators are directly related to the durability and service life of linen products (such as clothing, home textiles and industrial fabrics), and are the key parameters for measuring whether they can meet the requirements of specific uses.

Colour fastness: Tests the ability of the colour of the dyed or printed linen cloth to resist external factors. Conventional tests include rubbing fastness (dry/wet), soaping fastness, perspiration fastness, water spot fastness and light fastness. Good colour fastness is the basic requirement to ensure that the product does not fade or stain in use, and is related to the product quality and consumer experience.

Dimensional change rate (shrinkage): Determines the percentage change of the length or width of the linen cloth in the warp and weft directions after specific washing and drying treatments. Bast fibre has high hygroscopicity and is prone to shrinkage. This test is crucial for finished products with high dimensional stability requirements such as garments and bed sheets, and is the basis of the pre-shrinking process.

Appearance quality and defects: The surface of the linen cloth is inspected by visual inspection or instruments, identifying various appearance defects such as coarse yarns, fine yarns, streak shadows, holes, stains, colour differences and bowing and skewing. Scoring and grading are carried out according to the relevant product standards (such as GB/T 2696), directly determining the commercial grade and value of the product.

Formaldehyde content and pH value: As the core items of ecological safety testing, the formaldehyde content test ensures that the free formaldehyde in the product does not exceed the limit, to protect consumer health. The pH value test checks whether the acidity and alkalinity of the fabric is in the range suitable for human skin (usually 4.0-7.5), avoiding skin irritation caused by being too acidic or too alkaline.

Testing Scope

Pure bast fibre fabrics: Refers to fabrics woven from a single type of bast fibre (such as 100% flax and 100% ramie). During testing, the purity of the fibre needs to be confirmed as the focus, and its unique properties such as the coolness, moisture absorption and quick drying, and relatively high rigidity are evaluated according to the characteristic standards of pure bast fibre fabrics.

Bast fibre blended/interwoven fabrics: Products blended or interwoven with bast fibre and other fibres such as cotton, wool, silk, polyester and viscose. Testing needs to precisely analyze the content of each component, and comprehensively evaluate the performance changes brought by blending, such as improving the wrinkle resistance of pure bast fibre, increasing elasticity or reducing cost.

Bast fibre garments and accessories: Covering various finished products made mainly of linen cloth, such as shirts, trousers, dresses and scarves. In addition to the fabric performance, testing also needs to focus on the appearance quality of the finished product, sewing strength, the safety of accessories such as buttons and the standardization of the label marking.

Bast fibre home textiles: Including bed sheets, quilt covers, curtains, tablecloths and placemats. The test items focus on the performance related to the use scenarios, such as washing fastness, dimensional stability, abrasion resistance and flame retardancy (especially decorative fabrics such as curtains).

Industrial linen cloth and products: Linen cloth used in the fields of industry, agriculture and packaging, such as canvas, filter cloth, gunny sacks and interlinings. The testing focus is on its special functionality, such as high strength, high abrasion resistance, specific filtration precision and the effect of mildew-proof and anti-corrosion treatment, to meet the demanding industrial environment requirements.

Bast fibre yarns: As the raw material of linen cloth, the testing of bast fibre yarns is the upstream link of quality control. The main test items include the yarn linear density, twist, strength, evenness and appearance defects, and its quality directly determines the subsequent weaving efficiency and fabric quality.

Testing Methods

Chemical dissolution method (FZ/T 01057.4): Using the difference in the solubility of different fibres in specific chemical reagents, the content of each component in the bast fibre blended fabric is quantitatively analyzed. For example, 75% sulfuric acid is used to dissolve cellulosic fibres such as viscose and cotton, while the loss rate of the bast fibre needs to be calibrated with correction factors. It is the preferred method for arbitration and precise quantitative analysis.

Microscopic observation method (FZ/T 01057.3): A biological microscope or scanning electron microscope is used to observe the longitudinal morphology and cross-section characteristics of the fibre, and qualitatively or semi-quantitatively identify the type of bast fibre. The cross-section shapes (polygonal, kidney-shaped, etc.) and the longitudinal nodes and transverse joints of different bast fibres are the key basis for identification.

Strip method (GB/T 3923.1): The classic method for determining the breaking strength and elongation at break of fabrics. A specimen of a specified size is clamped on a constant rate of extension strength tester and pulled until breakage, recording the maximum force and elongation. This method can effectively simulate the sustained tensile force that the fabric is subjected to during wearing and use.

Rubbing fastness test method (GB/T 3920): Standard white cotton cloth in dry and wet states is wrapped on the rubbing finger, and reciprocating rubbing is carried out on the dyed linen cloth specimen under a certain pressure. Then the staining grade of the stained cotton cloth is rated with a grey scale, evaluating the degree of dye shedding under the action of rubbing.

Washing dimensional change rate test method (GB/T 8628-8629): A specimen marked with dimensions is treated according to the specified washing procedure (water temperature, mechanical action and detergent) and drying method (line drying, tumble drying and ironing). After the treatment, the distance between the marked points is measured and the dimensional change percentage is calculated, simulating the stability after household washing.

Gas chromatography method or spectrophotometric method: Used to precisely determine the free formaldehyde content in the linen cloth. Usually, the water extraction method is used to extract formaldehyde from the sample, and after the extract reacts with a color-developing reagent, the absorbance is measured with a spectrophotometer at a specific wavelength; or a gas chromatograph is used for high-sensitivity analysis, ensuring that the result complies with the limits of mandatory standards such as GB 18401.

Testing Standards

Domestic Standards:

1. GB/T 3923.1-2013, Textiles — Tensile properties of fabrics — Part 1: Determination of breaking force and elongation at breaking force using the strip method

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

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

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

International Standards:

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

2. 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 universal material testing machine: The core equipment for mechanical property tests of the fabric such as tension, tearing and bursting. Through precision sensors and a control system, it can precisely load and record the load-displacement curve, calculate various strength indicators and elongation, with high data repeatability and accuracy.

Standard light source cabinet: Provides an observation environment with standard light sources such as D65, TL84, CWF and UV, used for visually rating the colour difference, staining/fading grades of the colour fastness and appearance defects of the linen cloth. Comparing under a unified light source can avoid the subjective rating errors caused by changes in the ambient light.

Rubbing fastness tester: An instrument dedicated to rubbing fastness testing, which can precisely control the pressure, stroke and reciprocating speed of the rubbing finger. Its core components are the standard rubbing finger and replaceable rubbing cloth, ensuring the consistency of the test conditions and the comparability of the results.

Fabric shrinkage testing machine (automatic shrinkage machine): Can programmably control parameters such as the washing temperature, time, water level and agitation speed, simulating standard or custom washing procedures. Some high-end models integrate washing, spin-drying and drying in one unit, with a high degree of automation, greatly improving the testing efficiency and consistency.

pH meter and extractor: Combined equipment for determining the pH value of the aqueous extract of textiles. After the shredded specimen is oscillated and extracted in deionized water, the acidity and alkalinity of the extract is directly measured with a calibrated precision pH electrode. The operation is simple and the results are accurate and reliable.

Biological microscope and fibre fineness analyzer: The biological microscope is used to observe the fibre morphology for type identification; the fibre fineness analyzer (such as the optical projection method or laser scanning method) can precisely measure the diameter or linear density of the bast fibre, providing key data for evaluating the quality and spinning performance of the bast fibre.