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CAN CGSB 4.2 No. 57-M90 (2013): Textile Colourfastness to Light Testing Using Xenon Arc Lamp
A Comprehensive Technical Overview of Canada’s Standard for Artificial Lightfastness Evaluation
Scope and Purpose
CAN CGSB 4.2 No. 57-M90 (2013) is a Canadian standard developed by the Canadian General Standards Board (CGSB) that specifies a method for determining the colourfastness of textiles to the action of artificial light. The test is conducted using a xenon arc lamp that simulates the spectral distribution of natural daylight, including ultraviolet (UV) radiation. The standard applies to all textile materials—fibres, yarns, fabrics, and finished articles—and is widely used in quality control, product development, and compliance testing within Canada.
The method is technically equivalent to ISO 105-B02 and AATCC TM 16.3, though it includes specific conditioning and evaluation criteria tailored to Canadian climatic conditions. The standard covers exposure of test specimens and blue wool reference materials to controlled cycles of light and darkness under defined temperature and humidity conditions, followed by assessment of colour change using grey scales or instrumental measurement.
Technical Requirements and Test Conditions
Test Apparatus
The core instrument is a xenon arc lamp fitted with both outer and inner filters to approximate the spectral power distribution of daylight (e.g., CIE 1.1 D65). The apparatus must include:
- A light source with irradiance control (typically 40–50 W/m² at 420 nm).
- A black panel thermometer (BPT) or black standard thermometer (BST) to regulate the maximum temperature.
- A humidity control system capable of maintaining relative humidity (RH) at either low (35 ± 5%) or high (90 ± 5%) conditions as required.
- A specimen holder for mounting test samples and blue wool references (e.g., L2 to L9) on a rotating drum.
Specimen Preparation and Mounting
For each test, two or more specimens of the textile material are cut to fit the specimen holder. When the material is expected to be sensitive to humidity, two sets of specimens are used: one exposed under low humidity conditions and the other under high humidity. The specimens are backed with a white cardboard or metal backing to ensure uniform heat transfer. The blue wool references are similarly mounted, and the entire assembly is placed in the test chamber.
Exposure Conditions
The standard defines two primary exposure cycles depending on the intended end-use environment:
| Parameter | Standard Lightfastness (Low Humidity) | High Humidity Cycle |
|---|---|---|
| Irradiance at 420 nm | 1.10 ± 0.03 W/m² | 1.10 ± 0.03 W/m² |
| Black panel temperature | 50 ± 2 °C | 50 ± 2 °C |
| Relative humidity | 35 ± 5% | 90 ± 5% |
| Light/dark cycle | Continuous light (or dark cycles if needed) | 18 min light / 102 min dark (repeat) |
| Minimum exposure duration | Until blue wool L4 fades to contrast 4 on grey scale | Same, or until specified stage |
Evaluation of Colour Change
After exposure, the colour difference between the exposed and unexposed parts of each specimen is assessed visually using the CGSB 4.2 No. 21 Grey Scale for Assessing Change in Colour (equivalent to ISO 105-A02). Instrumental colour measurement can also be used, applying the CIELAB ΔE* colour difference formula with specified tolerances. The result is expressed as a lightfastness rating e.g., “4 (ISO)”, or “L4” on the blue wool scale.
Tip: When evaluating lightly coloured or fluorescent textiles, always use instrumental measurement to avoid subjectivity. Ensure the spectrophotometer is calibrated daily and configured with D65 illuminant and 10° standard observer.
Implementation Highlights
Calibration and Maintenance
Xenon arc lamps require periodic calibration to maintain the specified irradiance. The standard recommends:
- Daily check of black panel temperature and humidity sensors against reference instruments.
- Replacement of filters and lamp after every 1500–2000 hours of operation, or earlier if irradiance drifts.
- Routine cleaning of specimen holders and chamber walls to prevent contamination.
Conditioning
Before exposure, specimens must be conditioned in a standard atmosphere (20 ± 2 °C, 65 ± 4% RH) for at least 24 hours. For the high-humidity cycle, specimens are pre-wetted to achieve the required moisture content. This step is critical for materials that undergo phototendering or colour change influenced by moisture.
Reporting
The test report must include:
- Reference to CAN CGSB 4.2 No. 57-M90 (2013).
- Type of light source (xenon arc, filtered).
- Exposure cycle used (low or high humidity).
- Blue wool reference employed and its fade rating.
- Number of specimens and evaluation method (visual or instrumental).
- Lightfastness grade and any deviations from the standard.
Warning: Do not use mercury vapour or carbon arc lamps as substitutes for the xenon arc. Their spectral output differs significantly from daylight and will lead to erroneous colourfastness ratings, potentially causing non-compliance with Canadian regulatory requirements.
Best Practice: For maximum reproducibility, always run two complete exposure series (duplicate specimens) and report the median rating. Interlaboratory comparisons have shown that duplicate testing reduces variability by up to 30%.
Compliance and Certification Notes
Accreditation
Laboratories performing tests to CAN CGSB 4.2 No. 57-M90 (2013) should be accredited by the Standards Council of Canada (SCC) or an equivalent body. The standard is referenced in many Canadian procurement specifications for uniforms, upholstery, and industrial textiles. Testing to this standard may be required for products bearing the “Canada” label or sold to government agencies.
Deviations
Any modification to the test conditions (e.g., using a different filter combination, altering the humidity setting, or extending the exposure time) must be clearly documented in the report. If the standard is used for regulatory compliance, deviations may invalidate the test results unless a written waiver is obtained from the commissioning authority.
Critical: The standard does not allow combined light‑and‑wet series (rain tests) unless specified in the product standard. If wet lightfastness is required (e.g., for swimwear or outdoor furniture fabrics), refer to CAN CGSB 4.2 No. 58 (which covers colourfastness to light and perspiration). Mixing procedures will produce non-compliant results.
Frequently Asked Questions
Q: What is the difference between CAN CGSB 4.2 No. 57-M90 (2013) and ISO 105-B02?
A: The two standards are technically equivalent in terms of apparatus, procedures, and evaluation. However, the Canadian standard includes more detailed instructions for humidity control to reflect Canada’s variable climate, and it specifies the use of SCC-accredited laboratories for compliance. The blue wool references and grey scales are interchangeable.
A: The two standards are technically equivalent in terms of apparatus, procedures, and evaluation. However, the Canadian standard includes more detailed instructions for humidity control to reflect Canada’s variable climate, and it specifies the use of SCC-accredited laboratories for compliance. The blue wool references and grey scales are interchangeable.
Q: How many test specimens are required?
A: A minimum of two specimens is required for the standard procedure. When testing for both low‑ and high‑humidity sensitivity, two additional specimens are needed. For materials with a directional colour effect (e.g., pile or knit), at least four specimens oriented in different directions are recommended.
A: A minimum of two specimens is required for the standard procedure. When testing for both low‑ and high‑humidity sensitivity, two additional specimens are needed. For materials with a directional colour effect (e.g., pile or knit), at least four specimens oriented in different directions are recommended.
Q: Can the test be accelerated by using higher irradiance?
A: No. The irradiance at 420 nm must be kept within the specified tolerance of 1.10 ± 0.03 W/m². Increasing the irradiance may cause unrealistic fade patterns and invalidate the correlation with natural daylight exposure.
A: No. The irradiance at 420 nm must be kept within the specified tolerance of 1.10 ± 0.03 W/m². Increasing the irradiance may cause unrealistic fade patterns and invalidate the correlation with natural daylight exposure.
Q: Is this standard mandatory for all textile products sold in Canada?
A: Not universally, but it is mandatory for textiles procured by the Government of Canada (e.g., under the Treasury Board’s environmental purchasing policy) and for certain regulated products like children’s sleepwear and occupational safety garments. Many retailers also require compliance as a condition of sale.
A: Not universally, but it is mandatory for textiles procured by the Government of Canada (e.g., under the Treasury Board’s environmental purchasing policy) and for certain regulated products like children’s sleepwear and occupational safety garments. Many retailers also require compliance as a condition of sale.
This article is based on the published version of CAN CGSB 4.2 No. 57-M90 (2013) with reaffirmation year 2013. Always consult the official standard for complete wording. Footer year: 2026.