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CAN CGSB 4.2 No. 74-2011: Colour Fastness to Light – Xenon Arc Lamp Test Method
Comprehensive Technical Guide to the Canadian Standard for Textile Light Fastness Testing
CAN CGSB 4.2 No. 74-2011 is a Canadian national standard developed by the Canadian General Standards Board (CGSB) that specifies a method for determining the colour fastness of textiles to artificial light simulating daylight. The test method employs a xenon arc lamp as the light source and is technically harmonized with international standards such as ISO 105 B02 and AATCC TM 16.3. This standard is widely adopted across the Canadian textile industry for quality control, product development, and compliance with procurement requirements.
Scope and Application
The standard applies to all textile materials, including fabrics, yarns, and fibres, regardless of their composition or structure. It provides two sets of exposure conditions—one for interior (ambient) use and one for exterior (weather-resistant) applications. The method assesses the colour change resulting from exposure to a controlled light source under specified conditions of temperature and humidity.
The test is intended to produce results that correlate with the fading observed in real-world indoor exposure through window glass. Although the method does not replicate outdoor weathering in its full variability, it serves as a reliable screening tool for photostability and is referenced in many product specifications and performance standards across Canada.
Technical Requirements and Test Procedure
Test Apparatus
- Light source: A xenon arc lamp with an optical filter system (borosilicate quartz inner filter and soda lime outer filter) to simulate the spectral distribution of global daylight.
- Temperature measurement: A black standard thermometer (BST) or black panel thermometer (BPT) is used to control the temperature at the specimen surface.
- Humidity control: The chamber must maintain a specified relative humidity (RH) to ensure reproducible fading rates for moisture-sensitive dyes.
- Irradiance measurement: Sensors monitor the irradiance at 420 nm or in the 300–400 nm range to maintain constant exposure energy.
- Sample mounting: Specimens are placed on a non-fluorescent white card or perforated backing plate, with the test face oriented toward the light source.
Test Specimens
- Specimens shall have minimum dimensions of 70 mm × 100 mm (or as required by the evaluation method).
- Each specimen is accompanied by a reference blue wool scale (grades 1 to 8) or a suitable control material provided by the test requester.
- A minimum of three specimens per sample is recommended for statistical confidence.
Exposure Conditions
| Parameter | Interior (Ambient) Exposure | Exterior (Weathering) Exposure |
|---|---|---|
| Irradiance (at 420 nm) | 1.10 W/m²/nm ± 0.05 | 1.10 W/m²/nm ± 0.05 |
| Black standard temperature | 47°C ± 3°C | 65°C ± 3°C |
| Relative humidity | 40% ± 5% | 60% ± 10% |
| Chamber air temperature | 35°C ± 3°C | 45°C ± 3°C |
| Exposure cycle | Continuous light | Continuous light |
Periodic rotation of specimens within the chamber is required to ensure uniform exposure. The standard defines multiple options for exposure duration based on fading units or specific customer requirements.
Evaluation
After exposure, the colour change is assessed under standard illumination using either:
- Grey Scale for Colour Change – rating from 1 (severe change) to 5 (negligible change).
- Blue Wool Scale – rating from 1 (very low light fastness) to 8 (outstanding light fastness) by comparing the fading of the specimen to that of the blue wool references.
Interim assessments may be made at intervals to track fading progression. The final rating corresponds to the endpoint specified in the relevant product specification or by the customer.
Implementation Highlights
| Parameter | CAN CGSB 4.2 No. 74-2011 | ISO 105 B02:2014 | AATCC TM 16.3-2020 |
|---|---|---|---|
| Light source | Xenon arc lamp | Xenon arc lamp | Xenon arc lamp |
| Optical filters | Borosilicate + soda lime | Borosilicate + soda lime | Borosilicate + soda lime |
| Irradiance control | Monitored at 420 nm or total UV | Monitored at 420 nm | Monitored at 420 nm |
| Black standard temp. (interior) | 47°C ± 3°C | 47°C ± 3°C | 47°C ± 3°C |
| Relative humidity (interior) | 40% ± 5% | 40% ± 5% | 40% ± 5% |
| Endpoint determination | Blue wool or Grey Scale | Blue wool or Grey Scale | Blue wool or Grey Scale |
| Evaluation scale | 1–8 (blue wool) / 1–5 (grey scale) | 1–8 / 1–5 | 1–8 / 1–5 |
Calibration and Quality Control
- Regular calibration of BST, humidity sensors, and irradiance meters is essential for repeatable results.
- Certified reference blue wool standards (e.g., ISO 105 B02 or AATCC Blue Wools) should be used to verify the performance of the test apparatus.
- Laboratories are encouraged to participate in interlaboratory proficiency programs to maintain alignment with the global textile testing community.
Common Pitfalls
- Inconsistent sample mounting can produce shadows or non-uniform fading.
- Using the wrong filter system alters the spectral distribution and invalidates the test.
- Failing to monitor humidity leads to erratic fading, especially for dyes sensitive to moisture.
Key Insight: CAN CGSB 4.2 No. 74-2011 ensures that Canadian textile products meet the photostability requirements expected by consumers and industry, reducing returns due to fading.
Pro Tip: For reproducible results, condition the test specimens at standard atmospheric conditions (20°C ± 2°C, 65% ± 4% RH) for at least 4 hours before mounting.
Common Error: Failing to monitor the black standard temperature continuously can result in deviations that invalidate the entire exposure test.
Non-Compliance Risk: Using a xenon arc lamp beyond its recommended service life without performance verification can compromise spectral output and lead to erroneous pass/fail decisions.
Compliance Notes and Accreditation
Laboratories conducting tests according to this standard should operate under a quality management system complying with ISO/IEC 17025. The test report must clearly state the exposure conditions used, the method of evaluation (Grey Scale or Blue Wool), and the final light fastness rating. For product certification, reference to CAN CGSB 4.2 No. 74-2011 is often accompanied by other CGSB textile performance standards.
Since the 2011 revision, emphasis has been placed on documenting any deviations from the standard parameters and on validating that the test apparatus is capable of maintaining the specified irradiance, temperature, and humidity throughout the exposure period.
Frequently Asked Questions
Q: What is the main difference between CAN CGSB 4.2 No. 74-2011 and previous editions?
A: The 2011 edition introduced more stringent requirements for irradiance monitoring in the 300–400 nm range and aligned the test conditions with the latest international standards for better interlaboratory harmonization.
A: The 2011 edition introduced more stringent requirements for irradiance monitoring in the 300–400 nm range and aligned the test conditions with the latest international standards for better interlaboratory harmonization.
Q: Can this standard be used for automotive interior textiles?
A: While the standard includes exterior exposure conditions, automotive specifications often require SAE J2412 or separate cycles. However, some automotive laboratories use CGSB 4.2 No. 74 with modified parameters after mutual agreement.
A: While the standard includes exterior exposure conditions, automotive specifications often require SAE J2412 or separate cycles. However, some automotive laboratories use CGSB 4.2 No. 74 with modified parameters after mutual agreement.
Q: How does humidity affect light fastness results?
A: Many textile dyes are sensitive to moisture; increased humidity can accelerate fading reactions. The standard requires strict humidity control (±5%) to ensure reproducible fading rates.
A: Many textile dyes are sensitive to moisture; increased humidity can accelerate fading reactions. The standard requires strict humidity control (±5%) to ensure reproducible fading rates.
Q: Is there a correlation between the xenon arc test and outdoor exposure?
A: The xenon arc test provides a good correlation with indoor daylight exposure through window glass. For outdoor applications, it serves as a screening tool but cannot fully replicate the variable effects of weather; supplementary outdoor testing or specific weathering standards should be considered.
A: The xenon arc test provides a good correlation with indoor daylight exposure through window glass. For outdoor applications, it serves as a screening tool but cannot fully replicate the variable effects of weather; supplementary outdoor testing or specific weathering standards should be considered.
Note: This article is for informational purposes only. For official testing requirements, refer to the full text of CAN CGSB 4.2 No. 74-2011 published by the Canadian General Standards Board. (2026)