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CAN CGSB 4.2 No. 28.2-M91 (2013) – Textile Test Method for Colourfastness to Light
Understanding the Xenon Arc Lamp Procedure for Evaluating Colour Change in Textiles
Scope and Application
CAN CGSB 4.2 No. 28.2-M91 (2013) is a test method that specifies the procedure for determining the resistance of the colour of textiles to the action of light, using an artificial light source – the xenon arc lamp. It is part of the CAN/CGSB-4.2 series of textile test methods published by the Canadian General Standards Board. Originally published in 1991, it was reaffirmed in 2013 to confirm its continued relevance and technical validity.
The standard is applicable to all types of textiles, including woven, knitted, and nonwoven fabrics, yarns, and coloured components. It provides a laboratory method that simulates the effects of natural daylight through the use of an artificial light source, thereby enabling consistent and reproducible assessment of colourfastness to light. The method is particularly critical for manufacturers, importers, and regulatory bodies involved in quality assurance and certification for the Canadian market.
Technical Requirements and Test Procedure
2.1 Apparatus
The test requires a xenon arc lamp system equipped with appropriate filters (e.g., daylight or window glass filters) to produce a spectral distribution similar to natural daylight. The exposure chamber must include a black panel thermometer for temperature monitoring, humidity control, and a device for measuring and controlling irradiance. Specimen holders must be designed to avoid shadowing and to allow uniform exposure across all test pieces.
2.2 Test Specimens
Specimens are cut to dimensions appropriate for the specimen holder, typically 50 mm × 50 mm or as required. Each specimen is mounted on a card or in a holder with the face exposed to the light source. Blue wool references (No. 1 to No. 8) are used as standard fading controls. The specimens and blue wool strips are conditioned in a standard atmosphere (20±2 °C, 65±4% RH) before exposure.
2.3 Exposure Conditions
The exposure parameters are set according to the requirements of the standard and the intended end-use of the textile. Continuous or alternating light/dark cycles may be used, depending on the type of textile. The table below summarises the typical conditions specified in the standard.
| Parameter | Requirement |
|---|---|
| Light Source | Xenon arc lamp with daylight or window‑glass filters |
| Irradiance Control | Monitored at 420 nm or broadband 300–400 nm |
| Black Panel Temperature | 50 ± 2 °C |
| Chamber Air Temperature | 45 ± 2 °C |
| Relative Humidity | 50 ± 5 % |
| Light/Dark Cycle | Continuous light exposure, unless otherwise specified |
2.4 Evaluation
After exposure, specimens are removed and compared with unexposed originals. Colour change is rated using the grey scale (1 to 5) or by counting the number of the blue wool reference that shows a similar colour change. The standard defines the endpoint as the exposure level at which the contrast of the blue wool reference corresponds to a grade of 4 on the grey scale for colour change. Test duration is determined by the blue wool fading, typically requiring 20–100 hours of exposure, depending on the lightfastness of the material.
Tip: Prior to exposure, condition all specimens and blue wool references in a standard atmosphere for at least 24 hours to reach moisture equilibrium. This step is critical for consistent fade results.
Implementation Highlights
3.1 Equipment Calibration
Regular calibration of the irradiance sensor, black panel thermometer, and humidity sensor is essential. The xenon lamp filters must be replaced after a specified number of hours to maintain spectral quality. A calibrated reference material should be exposed periodically to verify system performance.
3.2 Specimen Mounting
Specimens must be mounted flat and secured so that they do not shift during the rotation cycle. For fabrics, care should be taken to avoid stretching or distortion. When using multiple specimens, their positions are rotated periodically to ensure uniformity of exposure across all samples.
3.3 Use of Blue Wool References
Blue wool references (e.g., BS 1006 or AATCC) are exposed alongside the test specimens. The standard requires at least one blue wool reference from No. 1 (lowest lightfastness) to No. 8 (highest). The reference that fades to a defined contrast determines the exposure endpoint and provides a basis for grading the test specimen.
Warning: Overloading the exposure chamber with too many specimens can impede airflow and cause uneven distribution of temperature and humidity, leading to inaccurate results.
Good Practice: Maintain a log of exposure runs with details of lamp hours, filter replacements, and calibration checks. This traceability supports accreditation and internal quality audits.
Critical: Failure to control humidity within the specified tolerance can significantly alter the fading behaviour of some dyes, especially those sensitive to moisture. Always verify the chamber conditions before each exposure.
Compliance and Quality Assurance Notes
Compliance with CAN CGSB 4.2 No. 28.2-M91 (2013) is often required for textile products entering the Canadian market, particularly when performance claims regarding colourfastness are made. Laboratories performing this test must be accredited to ISO/IEC 17025 and include this method in their scope of accreditation.
The method is technically similar to international standards such as ISO 105-B02, AATCC 16.3, and JIS L 0843. However, users should be aware of key differences in exposure conditions, rating methods, and specimen mounting requirements. For example, the CGSB method may specify different humidity levels or cycle patterns compared to ISO 105-B02. It is essential to follow the exact parameters of the CGSB standard when claiming compliance with the Canadian standard.
The reaffirmation of the 1991 edition in 2013 confirms that the methodology continues to meet the technical needs of the textile industry, providing a reliable basis for quality control, product labelling, and import regulation. As of 2026, this standard remains active and is widely referenced in Canadian textile specifications.
Q: How does this standard differ from ISO 105-B02?
A: While both use a xenon arc lamp, CAN CGSB 4.2 No. 28.2-M91 (2013) may prescribe slightly different humidity levels, specimen rotation intervals, and criteria for endpoint determination. Users must consult the specific CGSB document to ensure compliance for Canadian market requirements.
A: While both use a xenon arc lamp, CAN CGSB 4.2 No. 28.2-M91 (2013) may prescribe slightly different humidity levels, specimen rotation intervals, and criteria for endpoint determination. Users must consult the specific CGSB document to ensure compliance for Canadian market requirements.
Q: What blue wool rating is typically required for apparel textiles?
A: For general apparel, a rating of at least 4 to 5 on the blue wool scale is common. Home furnishings and automotive textiles may require higher ratings (e.g., 6 or 7) due to more stringent lightfastness expectations. The specific requirement is usually defined by the buyer or in the product specification.
A: For general apparel, a rating of at least 4 to 5 on the blue wool scale is common. Home furnishings and automotive textiles may require higher ratings (e.g., 6 or 7) due to more stringent lightfastness expectations. The specific requirement is usually defined by the buyer or in the product specification.
Q: Is this test method suitable for all fibre types?
A: Yes, it can be applied to natural, synthetic, and blended fibres. However, certain fibres (e.g., wool, silk) or dyes may be sensitive to heat or moisture, so exposure parameters must be carefully controlled to avoid unrealistic degradation. In such cases, a reduced black panel temperature or a modified humidity cycle may be agreed upon between parties.
A: Yes, it can be applied to natural, synthetic, and blended fibres. However, certain fibres (e.g., wool, silk) or dyes may be sensitive to heat or moisture, so exposure parameters must be carefully controlled to avoid unrealistic degradation. In such cases, a reduced black panel temperature or a modified humidity cycle may be agreed upon between parties.
Q: Can this method be used for quality control in production?
A: Absolutely. The test provides a reproducible quantitative assessment of lightfastness. It is widely used for internal quality control, pre‑shipment testing, and conformity assessment. Many retailers and brands require suppliers to certify colourfastness results generated by ISO/IEC 17025 accredited laboratories using this method.
A: Absolutely. The test provides a reproducible quantitative assessment of lightfastness. It is widely used for internal quality control, pre‑shipment testing, and conformity assessment. Many retailers and brands require suppliers to certify colourfastness results generated by ISO/IEC 17025 accredited laboratories using this method.
Last updated: 2026