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CAN CGSB 4.2 No. 27.3-2010: Evaluating Colourfastness of Textiles to Light Using Xenon Arc Lamp Test
A Comprehensive Overview of the Canadian Standard for Lightfastness Testing
1. Scope and Purpose
CAN CGSB 4.2 No. 27.3-2010, part of the Canadian General Standards Board (CGSB) series of textile test methods, specifies a procedure for determining the colourfastness of textile materials to the action of artificial light using a xenon arc lamp. This standard is designed to simulate the spectral distribution of natural daylight, providing a laboratory accelerated test that predicts the performance of dyed, printed, or otherwise coloured textiles when exposed to light during end-use.
The method is applicable to all types of textile materials—fibres, yarns, and fabrics—regardless of their dyeing or finishing process. It is particularly important for manufacturers, retailers, and importers who need to ensure colour stability in products ranging from apparel and home furnishings to automotive textiles and outdoor gear. The test assesses the resistance of colour to fading or change when subjected to controlled irradiance, temperature, and humidity conditions.
While CAN CGSB 4.2 No. 27.3-2010 is a standalone Canadian standard, it is technically aligned with the international benchmark ISO 105-B02:2014 and the U.S. AATCC 16.3 test methods. Laboratories accredited under these protocols can generally demonstrate conformity to this CGSB standard with appropriate cross-referencing.
Note: This standard is not intended for evaluating the colourfastness of materials to outdoor weathering, which involves other environmental factors beyond light. For outdoor exposure testing, refer to CAN CGSB 4.2 No. 27.4 or ISO 105-B04.
2. Technical Requirements and Test Conditions
2.1 Xenon Arc Apparatus
The test requires a xenon arc lamp equipped with optical filters to simulate the ultraviolet and visible spectrum of natural daylight (approx. 300–800 nm). The apparatus must be capable of maintaining specified irradiance levels, typically monitored at 420 nm. Air-cooled or water-cooled lamps are acceptable provided the spectral distribution meets the standard’s requirements. The chamber must also control black standard temperature (BST) and relative humidity (RH) within tight tolerances.
2.2 Reference Materials
Colourfastness ratings are based on either the blue wool reference scale (grades 1–8) or the grey scale for colour change (grades 1–5). The blue wool references (L2 to L9) are dyed wool fabrics that exhibit known fading rates when exposed under controlled conditions. The grey scale provides a numerical rating of visual contrast. The standard requires the use of both systems for comprehensive evaluation.
2.3 Exposure Conditions
The table below summarises the standard exposure conditions specified in CAN CGSB 4.2 No. 27.3-2010:
| Parameter | Requirement | Tolerance |
|---|---|---|
| Irradiance at specimen level (420 nm) | 1.10 W/m²·nm | ±0.03 W/m²·nm |
| Black standard temperature (BST) | 47°C | ±3°C |
| Chamber air temperature | 35°C | ±3°C |
| Relative humidity (light phase) | 35 % RH | ±5 % RH |
| Relative humidity (wet phase, if applicable) | 65 % RH | ±5 % RH |
| Test duration (for midpoint rating) | Controlled by reference fade | — |
| Light/dark cycle | Continuous light | — |
For exposures requiring intermittent wetting (e.g., to simulate rainforest conditions), the standard provides an alternative cycling procedure. However, the base method uses continuous light exposure under dry conditions.
TIP: Even slight deviations in relative humidity can significantly alter fading rates. Used dyestuffs may respond differently, so strict adherence to humidity control is essential for comparability.
3. Implementation and Rating Procedure
3.1 Specimen Preparation
Test specimens (typically 100 mm × 50 mm) are cut from the textile material and mounted on flat, non-fluorescent holders. Blue wool references are mounted alongside the specimens on the same exposure mask to ensure identical exposure conditions. At least two specimens per sample are tested, and for woven fabrics, specimen lengths should be oriented in both warp and weft directions.
3.2 Exposure and Rating
The exposure is continued until the contrast between exposed and unexposed areas of the blue wool reference L4 (or another pre‑selected reference) reaches a prescribed difference, as evaluated against the grey scale. At this point, the exposure cycle stops, and the colour change of each test specimen is rated against both the blue wool scale and the grey scale for colour change. The lightfastness number is reported as the highest blue wool grade that still shows less contrast than the test specimen, or as a direct grey scale rating (e.g., GS 3–4).
The standard also permits an alternative rating by instrumental measurement (spectrophotometry). When this method is used, the colour difference is calculated using CIELAB ΔE*ab and converted to a visual rating using approved algorithms.
3.3 Evaluation of Results
The final result is expressed as a lightfastness number on the blue wool scale (1–8) or as a grey scale rating (1–5). A grade of 4 or higher on the blue wool scale is generally considered satisfactory for most apparel applications; for automotive or outdoor products, higher grades (6–8) may be required. The standard explicitly requires reporting both the rating and the exposure endpoint reference used.
SUCCESS: When both blue wool and grey scale ratings are performed, discrepancies between the two can reveal whether fading is due to hue shift or loss of chroma, aiding in root cause analysis.
4. Compliance, Quality Assurance, and Reporting
4.1 Laboratory Accreditation
Testing laboratories seeking accreditation to CAN CGSB 4.2 No. 27.3-2010 must demonstrate competence in operating xenon arc equipment, maintaining calibration of radiometers, thermometers, and hygrometers, and performing visual or instrumental assessments. The standard is referenced in many Canadian textile procurement contracts as the required test method for lightfastness compliance.
4.2 Interlaboratory Variability
Studies have identified that differences in black standard temperature (±2°C) and humidity (±5 % RH) are the most common sources of interlaboratory variation. To minimise such bias, the standard recommends that participating laboratories engage in proficiency testing programmes and use identical blue wool reference batches.
4.3 Test Report Elements
CAN CGSB 4.2 No. 27.3-2010 specifies the minimum information to be included in the test report:
- Reference to this standard (CAN CGSB 4.2 No. 27.3-2010);
- Identification of the textile sample (type, colour, direction);
- Exposure conditions (irradiance, temperature, relative humidity, light/dark cycle);
- Reference system used (blue wool and/or grey scale);
- Light fastness rating (blue wool grade or grey scale grade);
- Details of any deviation from the standard procedure.
WARN: Failure to document actual exposure conditions (e.g., a logged drift in humidity) may cause the test to be considered invalid. Always record continuous monitoring data.
DANGER: Never expose blue wool references to light outside the test apparatus. Pre‑exposure or contamination will result in invalid ratings and wasted test time.
Frequently Asked Questions
Q: How does CAN CGSB 4.2 No. 27.3-2010 differ from ISO 105-B02?
A: While both standards use a xenon arc lamp and blue wool references, the CGSB version includes specific references to Canadian procurement requirements and may permit minor tolerances that differ by region. In most aspects, the methods are technically interchangeable, but the official compliance for Canadian contracts must follow the CGSB document. Laboratories should verify the edition year and any annexes that introduce additional test cycles for wet exposure or high‑temperature conditions.
A: While both standards use a xenon arc lamp and blue wool references, the CGSB version includes specific references to Canadian procurement requirements and may permit minor tolerances that differ by region. In most aspects, the methods are technically interchangeable, but the official compliance for Canadian contracts must follow the CGSB document. Laboratories should verify the edition year and any annexes that introduce additional test cycles for wet exposure or high‑temperature conditions.
Q: Can this test be used for automotive interior textiles?
A: Yes, the test is suitable for automotive textiles, although many automakers require more severe exposure conditions (e.g., higher BST of 70–90°C per SAE J1885). The CGSB standard can be adapted by specifying a different black standard temperature and humidity, provided the deviation is documented. For strict automotive compliance, a dedicated standard such as SAE J2412 or ISO 105-B06 is often preferred.
A: Yes, the test is suitable for automotive textiles, although many automakers require more severe exposure conditions (e.g., higher BST of 70–90°C per SAE J1885). The CGSB standard can be adapted by specifying a different black standard temperature and humidity, provided the deviation is documented. For strict automotive compliance, a dedicated standard such as SAE J2412 or ISO 105-B06 is often preferred.
Q: What is the typical exposure time to achieve a lightfastness grade of 4 on the blue wool scale?
A: Under the standard conditions (BST 47°C, 35% RH, irradiance 1.10 W/m² at 420 nm), the blue wool L4 typically fades to a contrast equivalent to Grey Scale grade 3 after approximately 80–100 hours of continuous exposure. The actual time depends on lamp ageing and filter degradation, which is why the test endpoint is always controlled by the reference rather than a fixed clock.
A: Under the standard conditions (BST 47°C, 35% RH, irradiance 1.10 W/m² at 420 nm), the blue wool L4 typically fades to a contrast equivalent to Grey Scale grade 3 after approximately 80–100 hours of continuous exposure. The actual time depends on lamp ageing and filter degradation, which is why the test endpoint is always controlled by the reference rather than a fixed clock.
Q: Is it mandatory to use both blue wool and grey scale for rating?
A: The standard recommends both assessments for a complete evaluation, but the test report may be based solely on the blue wool scale if required by the customer. When only grey scale is reported, the blue wool references must still be used to determine the correct exposure endpoint, as specified in Clause 7.2 of the standard. Thus, the references are essential even if the final rating is expressed using the grey scale only.
A: The standard recommends both assessments for a complete evaluation, but the test report may be based solely on the blue wool scale if required by the customer. When only grey scale is reported, the blue wool references must still be used to determine the correct exposure endpoint, as specified in Clause 7.2 of the standard. Thus, the references are essential even if the final rating is expressed using the grey scale only.
Article last updated: 2026. This information is provided for general guidance and does not substitute the official text of CAN CGSB 4.2 No. 27.3-2010. For verification, always refer to the current edition published by the Canadian General Standards Board.