Cashmere Testing

Cashmere inspection mainly conducts scientific testing and analysis on fibre diameter and distribution, fibre length and short fibre content, non-cashmere fibre content, impurity content and cashmere content, colour and colour fastness, and strength and elongation properties, 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 diameter and distribution: This is the core indicator of the cashmere quality. By measuring the average diameter of the single fibres (in micrometres) and its dispersion degree (coefficient of variation), the fineness and uniformity are evaluated. The average diameter of the high-quality cashmere is usually less than 15.5 micrometres, with the concentrated distribution and delicate hand feel. The test report will list in detail the average diameter, standard deviation and diameter distribution histogram.

Fibre length and short fibre content: The fibre length of the cashmere affects the spinning performance and the quality of the finished products. The testing contents include the hand-arranged length, weighted mean length and the percentage of the short fibres (usually referring to the fibres with the length ≤30 mm). The cashmere with the long length and low short fibre content has high spinnability and good yarn strength, and is the important basis for the grade assessment.

Non-cashmere fibre content: This item aims to identify the purity of the cashmere products. The microscope method or scanning electron microscope method is used to identify and quantitatively analyse the other animal fibres mixed in, such as the wool, rabbit hair and yak down. In accordance with the relevant standards, the cashmere fibre content in the cashmere products must reach the specified proportion (such as above 95%) to be marked as the pure cashmere.

Impurity content and cashmere content: The impurity content refers to the mass percentage of the foreign matters such as the grass seeds, skin debris and sand in the raw cashmere. The cashmere content refers to the percentage of the washed cashmere fibres in the total mass of the raw cashmere. These two indicators are directly related to the utilization rate of the raw materials and the production cost, and are the basic data of the trade settlement and process design.

Colour and colour fastness: For the finished products or dyed cashmere, the colour characteristics and colour fastness need to be tested. Including the whiteness, colour difference (comparison with the original sample), as well as the colour fastness grades such as the colour fastness to soaping, rubbing and light. The poor colour fastness will cause the fading and staining of the product during wearing or washing, affecting the use value.

Strength and elongation properties: Measures the breaking strength (cN) and elongation at break (%) of the single cashmere fibres. Although the cashmere fibres are fine, their excellent strength and elongation properties are the basis for ensuring the durability of the yarns and fabrics. This data has the important reference value for the parameter setting of the subsequent spinning processes.

Testing Scope

Raw cashmere: Refers to the primary product grabbed from the goats without any processing. The testing mainly targets the basic indicators such as the cashmere content, impurity content, fibre diameter and length, and is used for the raw material purchase grading, trade settlement and preliminary processing process guidance.

Cashmere (dehaired): Refers to the clean cashmere after the raw cashmere undergoes the dehairing processing, which removes most of the coarse hairs and impurities. The testing focus is on the non-cashmere fibre content, fibre diameter, length and oil content, and it is the core basis for determining its grade as the worsted or woollen raw material.

Cashmere yarns: Including the pure cashmere yarns and cashmere blended yarns. In addition to the fibre composition content, the testing items also include the yarn linear density, twist, strength, evenness and hairiness, comprehensively evaluating its weavability and the performance of the final fabrics.

Cashmere knitted goods and woven goods: Covering the final consumer products such as the cashmere sweaters, scarves and coat fabrics. The testing scope is the most comprehensive, including the fibre composition qualitative and quantitative analysis, pilling performance, bursting strength, dimensional stability, colour fastness and marking standardization, ensuring that the products comply with the national mandatory standards and consumer safety requirements.

Accessories of the cashmere products: The composition testing is carried out on the decorative fibres and auxiliary materials on the cashmere products (such as the neck labels and sewing threads), preventing the shoddy substitution or false marking, and ensuring the consistency of the overall quality of the product with the claims.

Import and export trade batches: To meet the requirements of the customs supervision, international trade contracts and the regulations of the destination markets, the conformity inspection is carried out on the large-scale import and export cashmere raw materials, semi-finished products or finished products, usually executed in accordance with the international standards or the standards agreed by both parties of the transaction.

Testing Methods

Micro-projection method (diameter testing): In accordance with the standards such as GB/T 10685 or IWTO-8, the fibre cross-sections are placed under the projector, and the diameter is determined by measuring the width of the magnified image. This is the internationally common reference method, with the accurate and reliable results, and is commonly used for the arbitration inspection and instrument calibration.

Laser scanning fibre diameter analyser method (OFDA/Laserscan): A modern and efficient testing method. The laser beam is used to scan the flowing fibres, and through the light scattering principle, the diameters of a large number of fibres are rapidly measured and the distribution diagram is generated. This method is fast with good repeatability, and is widely used in the daily quality control of the enterprises.

Optical microscope composition analysis method: In accordance with the GB/T 16988 or ISO 17751 standard, based on the differences of the morphological characteristics such as the scale structure and medulla layer between the cashmere and the other animal fibres (mainly the wool), the identification and counting are carried out under the microscope, calculating the mass percentage of each component. This is the classic method for determining the pure cashmere content.

Scanning electron microscope method (SEM): When the optical microscope is difficult to identify and distinguish (such as the superfine wool and cashmere), the scanning electron microscope is used to observe the ultra-microstructures such as the height, density and edge morphology of the fibre surface scales, and the identification results are more precise. It is commonly used for the arbitration analysis of the difficult samples.

Hand-arranged length method: A traditional but intuitive length testing method. The fibre samples are arranged into a fibre bundle with one end aligned, evenly arranged on the black velvet board from the longest to the shortest, and the length arrangement diagram is drawn, thereby obtaining the various length indicators and the short fibre content. This method can intuitively reflect the fibre length distribution.

Single fibre strength testing method: A single fibre strength tester is used. Under the standard temperature and humidity conditions, a single fibre is clamped and stretched at a constant rate until it breaks, recording its breaking strength and elongation at break. This method has high requirements on the instrument precision and the skills of the operators.

Testing Standards

Domestic Standards:

1. GB/T 18267, Cashmere

2. GB/T 10685, Determination of animal fibre diameter — Projection microscope method

3. GB/T 16988, Quantitative determination for mixtures of special animal fibre and wool

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

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

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

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

International Standards:

1. ISO 17751, Textiles — Quantitative analysis of cashmere, wool, other special animal fibres and their blends

2. IWTO-8, Determination of mean fibre diameter — Microprojection method

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

4. 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

Optical micro-projector: Composed of a light source, condenser, objective lens, projection screen and micrometer scale, used for the reference measurement of the fibre diameter. During the operation, each fibre needs to be manually measured and recorded one by one. It is the "standard ruler" for calibrating the other rapid testing equipment, ensuring the accuracy and uniformity of the measured values of the testing system.

Laser fibre fineness analyser (such as the OFDA series): The core components include the laser generator, flowing sample chamber, CCD detector and high-speed image processing software. It can complete the diameter measurement and statistical analysis of thousands of fibres within a few minutes, greatly improving the testing efficiency. It is the standard equipment of the modern laboratories.

Biological microscope and stereomicroscope: Equipped with the high-resolution objective lenses and eyepiece micrometer scales, used for the fibre morphology observation and composition analysis. Due to its large depth of field and spacious operating space, the stereomicroscope is commonly used for sorting and observing the fibre bundles; the biological microscope is used for the scale structure observation at high magnification.

Scanning electron microscope (SEM): A high-end precision instrument, composed of an electron gun, vacuum system, detector and imaging system. It can generate the high-resolution three-dimensional fibre surface images, used for the precise identification of the superfine fibres. The samples usually need to undergo the gold sputtering conductive treatment.

Single fibre electronic strength tester: Equipped with a high-precision force sensor (with the range usually of 0-50 cN) and displacement sensor, and the grip distance and tensile speed can be precisely set. The testing environment needs to be in a constant temperature and humidity laboratory (such as the temperature of 20±2 °C and relative humidity of 65±4%), to eliminate the environmental interference.

Fibre length analyser (fibrograph or Almeter): Based on the photoelectric principle or mechanical combing principle, it rapidly determines the fibre length indicators. The fibrograph calculates the length distribution by measuring the light-blocking amount of the fibre bundle, with the extremely high speed; the Almeter obtains the data closer to the hand-arranged method through the automatic combing and weighing.