GB Standard Textile Composition Testing: Fiber Content Analysis Under Chinese National Standards

GB standard textile composition testing refers to the qualitative identification and quantitative determination of fiber content in textiles in accordance with China's national (GB) standards, principally the GB/T 2910 series for chemical analysis and GB/T 29862 for fiber content labeling. Accurate fiber composition data is a mandatory compliance requirement for textiles and apparel sold in the Chinese market and a fundamental element of product quality control. This guide explains the applicable standards, sample types, testing items, laboratory procedures, and frequently asked questions related to textile composition testing under the GB system.

Technical Overview

Fiber composition is one of the most closely scrutinized quality attributes of textile products in China. Under GB 5296.4, instructions for use of consumer products for textiles and apparel, and GB/T 29862, the national standard for the identification of fiber content, every textile product placed on the Chinese market must carry a fiber content label that accurately declares the types and percentages of constituent fibers. Verification of this declaration is performed through GB standard textile composition testing, typically carried out by accredited third-party laboratories or qualified in-house quality control facilities.

The technical basis of quantitative composition testing is the GB/T 2910 series of standards, which specifies quantitative chemical analysis methods for binary and ternary fiber mixtures and is substantially harmonized with the international ISO 1833 series. Qualitative fiber identification is governed by the FZ/T 01057 series, which covers burning tests, microscopic observation, solubility tests, and other identification techniques. The key standards in this field include:

• GB/T 29862, Textiles - Identification of Fiber Content: labeling rules, fiber naming, expression of results, and permitted tolerances
• GB 5296.4, Instructions for Use of Products of Consumer Interest - Part 4: Textiles and Apparel: mandatory labeling requirements including fiber content
• GB/T 2910 series, Quantitative Chemical Analysis: dissolution-based methods for specific fiber pairings, aligned with ISO 1833
• FZ/T 01057 series, Qualitative Identification of Textile Fibers: burning, microscopy, solubility, and instrumental identification methods
• GB/T 16988: quantitative determination of cashmere and wool mixtures by projection microscopy
• FZ/T 01101: determination of fiber content by physical separation methods
• GB/T 9994: conventional moisture regain values used to convert dry mass results into commercial mass percentages
• International references such as ISO 1833, ISO 17751, AATCC 20 and 20A, ASTM D629, EN ISO 1833, and JIS L 1030 for products intended for multiple markets

GB/T 29862 defines the tolerances permitted between labeled and measured fiber content. In general, a deviation of 5 percent is permitted for fibers labeled at or above 10 percent, and a deviation of 3 percent is permitted for fibers labeled below 10 percent, with additional specific provisions for low-content fibers, fillings, and decorative elements. Products whose measured composition falls outside these tolerances, or whose fiber names are non-standard, are treated as mislabeled and may trigger rectification, market withdrawal, or regulatory penalties under China's product quality legal framework.

Testing Samples

Correct sampling is critical because fiber content can vary between components of a single product. Samples must be representative of each labeled component, free from contamination, and sufficient in mass for replicate determinations. Typical sample categories include the following.

Greige and Finished Fabrics

Woven, knitted, and nonwoven fabrics in greige, dyed, printed, or finished states are the most common samples. Finishes, sizes, and softeners are removed during mandatory pre-treatment before analysis so that only fibrous material is quantified. Multi-layered or double-face fabrics are sampled by layer when each layer carries a separate fiber declaration.

Yarns and Fibers

Raw fiber lots, spun yarns, filament yarns, embroidery threads, and sewing threads are tested to verify blend ratios before weaving or knitting. Twisted and plied yarns are opened and conditioned before specimens are taken, and blends introduced at the spinning stage are verified at the yarn stage to prevent downstream labeling errors.

Garments and Home Textiles

Finished apparel, bedding, towels, curtains, and blankets are sampled component by component, including shell fabric, lining, filling, collar and cuff materials, and any auxiliary fabric declared on the label. Each component that carries its own fiber declaration requires a separate determination. Filled products such as quilts and pillows are additionally subject to filling content verification.

Specialty and Technical Textiles

Luxury animal fiber products such as cashmere, wool, silk, and their blends require microscopical verification in addition to chemical analysis. Coated, laminated, and functional textiles containing specialty fibers such as aramid, elastane, or high-tenacity polyesters require careful method selection because coatings and membrane layers can interfere with dissolution chemistry and must be removed or accounted for during pre-treatment.

Testing Items

A complete GB standard composition test program typically comprises the following items, which may be ordered individually or as a package depending on the compliance objective.

• Qualitative fiber identification: determination of every fiber type present in the sample using burning behavior, morphology, solubility, and instrumental confirmation
• Quantitative fiber content: determination of the mass percentage of each fiber in binary, ternary, or multi-component mixtures
• Label conformity assessment: comparison of measured results against the declared fiber content under the tolerance rules of GB/T 29862
• Specialty fiber confirmation: distinction between cashmere and wool, mulberry and tussah silk, and similar fibers requiring microscopical or morphological evidence
• Component-by-component determination: separate analysis of every labeled component of a multi-part product such as a lined jacket or a two-tone bedding set

Testing Methods

Qualitative Fiber Identification

Identification precedes quantification because the dissolution method can only be selected once the fiber types are known. Following the FZ/T 01057 series, the laboratory observes burning characteristics such as flame behavior, melting, odor, and residue ash; examines longitudinal and cross-sectional morphology under a light microscope; performs solubility screening using reagents such as hydrochloric acid, sulfuric acid, acetone, and dimethylformamide; and, where necessary, applies melting point determination or infrared spectroscopy to confirm man-made fibers. Combined evidence from at least two independent techniques is required for a defensible identification conclusion.

Quantitative Chemical Analysis Under the GB/T 2910 Series

The GB/T 2910 series quantifies fiber mixtures by selectively dissolving one component in a specified reagent while leaving the other component intact. The general procedure is as follows.

• Pre-treatment: non-fibrous matter such as oils, sizes, and finishes is removed with light petroleum solvent and water in accordance with GB/T 2910.1
• Drying and weighing: the cleaned specimen is dried in a ventilated oven at approximately 105 degrees Celsius to constant mass and weighed on an analytical balance to obtain the initial dry mass m1
• Selective dissolution: the specimen is treated with the reagent prescribed for the specific fiber pairing, for example 75 percent sulfuric acid for cellulose and polyester blends under GB/T 2910.11, 80 percent formic acid for polyamide blends under GB/T 2910.7, sodium hypochlorite for protein fiber blends under GB/T 2910.4, acetone for acetate blends under GB/T 2910.3, and dimethylformamide for certain acrylic, chlorofiber, and elastane blends under GB/T 2910.12
• Recovery: the insoluble residue is filtered through a sintered-glass crucible, rinsed neutral, dried to constant mass, and weighed to obtain the residue dry mass m2
• Calculation: the dry mass percentage of the insoluble fiber equals 100 multiplied by m2 multiplied by d divided by m1, where d is the correction factor that compensates for any slight attack of the reagent on the insoluble fiber; the dissolved fiber percentage is the balance to 100 percent
• Conversion: dry mass percentages are converted to commercial mass percentages using the conventional moisture regain values of GB/T 9994, which is the basis for fiber content declarations on labels

Ternary mixtures are analyzed under GB/T 2910.2 by applying two dissolution steps in sequence or in parallel and solving the resulting mass balance. Mixtures of four or more fibers are handled through sequential dissolution, combined chemical and physical separation, or method combinations developed and validated by the testing laboratory.

Physical Separation and Microscopical Methods

When fibers are mechanically separable, for example when a fabric interlaces yarns of different composition, the physical method of FZ/T 01101 allows the components to be separated by hand or with needles, then dried and weighed directly. Cashmere and wool mixtures, which share identical chemical behavior and cannot be separated chemically, are quantified by projection or scanning electron microscopy under GB/T 16988, with reference to ISO 17751 for internationally accepted practice. The analyst measures fiber diameter and evaluates scale pattern characteristics over a statistically sufficient number of fibers, typically at least one thousand, to estimate the mass proportion of each animal fiber species.

Quality Assurance of Results

GB standard composition testing requires replicate determinations, usually two specimens per component, with agreement within 1 percentage point in absolute terms. Reagent concentration, treatment temperature, and treatment time are tightly controlled because deviations shift the d factor and bias results. Accredited third-party laboratories operate under recognized accreditation schemes with documented traceability of balances, ovens, and volumetric equipment, and test reports state the applied method, d values, dry and commercial mass results, and a conformity conclusion against the fiber content label.

Applications

GB standard textile composition testing supports a wide range of commercial and regulatory objectives throughout the textile supply chain.

• Domestic market compliance: verifying fiber content labels before products are placed on the Chinese market in conjunction with the safety requirements of GB 18401
• Import and export verification: providing composition evidence for customs inspection, trade documentation, and alignment with ISO, ASTM, EN, and JIS requirements for destination markets
• Supplier and incoming quality control: confirming blend ratios of greige fabrics, yarns, and fibers at the point of procurement to prevent labeling errors downstream
• E-commerce platform compliance: satisfying composition documentation requests from online marketplaces that conduct periodic audits and product sampling
• Dispute resolution: supplying objective analytical evidence for commercial claims, customer complaints, and regulatory investigations
• Product development: benchmarking competitor constructions, validating new blend designs, and certifying specialty fiber claims such as pure cashmere or pure silk

FAQ

What is the difference between GB/T 2910 and ISO 1833?

The GB/T 2910 series is substantially harmonized with ISO 1833, and most parts adopt the same reagents, treatment conditions, and calculation principles. Minor differences may exist in reagent concentration, treatment temperature, or timing between editions, so the test report must always identify the exact method applied. For products sold in China, results should be reported under the GB designation.

How much sample is required for a composition test?

A full garment is preferred so that every labeled component can be sampled. For fabric submissions, at least 10 by 10 centimeters per component is typically requested, providing two replicate specimens of approximately 1 gram each. Specialty tests such as cashmere and wool microscopy may require additional material to obtain a representative fiber population.

What tolerances are allowed between the label and the measured fiber content?

Under GB/T 29862, a deviation of 5 percent is generally permitted for fibers labeled at 10 percent or more, and 3 percent for fibers labeled below 10 percent. Specific provisions apply to low-content fibers, decorative elements, and fillings, so the conformity conclusion is always assessed clause by clause against the full standard.

How is cashmere distinguished from sheep wool when both are protein fibers?

Chemical dissolution cannot separate them because they are chemically identical. Identification relies on microscopical evaluation of scale height, scale frequency, and fiber diameter under GB/T 16988 and ISO 17751. Because very fine wool can overlap with coarse cashmere morphologically, results are reported with appropriate technical caveats, and emerging protein-based techniques are increasingly used as supplementary evidence.

Can elastane or spandex content be measured under the GB system?

Yes. Elastane in blends is quantified using dedicated solvent-based methods within the GB/T 2910 framework, typically based on dimethylformamide or dimethylacetamide dissolution under controlled temperature. Elastane is usually present at low percentages, so its content is assessed against the low-content tolerance rules of GB/T 29862.

How long does GB composition testing take and what does the report include?

Standard turnaround is typically five to seven working days for routine chemical analysis, with microscopy-based animal fiber tests taking slightly longer. The report includes the qualitative identification, the quantitative method and its correction factors, dry mass and commercial mass percentages for every fiber, and a pass or fail conclusion against the declared fiber content, which can be bundled with GB 18401 safety testing for a complete market entry compliance package.