Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
CAN CGSB 4.2 No. 73.4-M91 (2013): Standard Test Method for Colourfastness to Light of Textiles – Xenon Arc Lamp
Comprehensive guide to the Canadian standard for accelerated lightfastness testing using xenon‑arc apparatus
Introduction
CAN CGSB 4.2 No. 73.4-M91 (2013) — part of the Canadian General Standards Board (CGSB) series on textile test methods — specifies the procedure for determining the resistance of textile colours to the action of artificial light. The method employs a xenon arc lamp that simulates the spectral distribution of natural daylight. This standard is widely referenced in Canadian product certification programs and is technically aligned with ISO 105-B02:1994 (with national modifications).
Scope
This standard applies to textiles of all kinds, including woven, knitted, and nonwoven fabrics, as well as yarns and fibres. It is intended for assessing colourfastness to light under controlled conditions using a filtered xenon arc lamp. The method covers both continuous light exposure and intermittent dark phases (simulating day/night cycles). It does not apply to tests using open-flame carbon arcs or mercury vapour lamps.
The document includes two exposure methods:
- Method A: Continuous exposure to light without dark periods.
- Method B: Alternating light and dark cycles (usually 20 h light / 4 h dark) to account for cyclic effects.
Technical Requirements
Apparatus
- Xenon arc lamp with appropriate filters (daylight or window-glass filter).
- Black standard thermometer (BST) or black panel thermometer (BPT).
- Humidity sensor and control system.
- Irradiance control (typically at 300–400 nm or 420 nm).
Test Conditions
| Parameter | Standard Condition | Tolerance |
|---|---|---|
| Black standard temperature | 45 °C | ±3 °C |
| Chamber air temperature | 35 °C | ±2 °C |
| Relative humidity | 50 % | ±5 % |
| Irradiance (300–400 nm) | 45 W/m² | ±2 W/m² |
| Exposure cycle (Method B) | 20 h light / 4 h dark | ±0.5 h |
Reference Materials
Colourfastness to light is assessed using the Blue Wool Reference (BWR) scale L2 to L9, in accordance with ISO 105-B08 (or equivalent CGSB standard). Each reference has a known lightfastness rating. The test specimen and reference materials are exposed simultaneously until a specified contrast is reached on the BWR.
Assessment
The change in colour of the specimen is evaluated using the Grey Scale for Assessing Change in Colour (ISO 105-A02 or CGSB 4.2 No. 2). The result is reported as a lightfastness rating from 1 (very poor) to 8 (outstanding).
Implementation and Calibration
Sample Preparation
- Condition specimens in a standard atmosphere (20±2 °C, 65±4 % RH) for at least 4 h before testing.
- Cut samples to fit the specimen holder; use opaque backing if required.
Tip: Always mount the specimen with the face to be tested exposed to the light source. If the material is not uniform, test multiple specimens to capture variability.
Calibration
The xenon arc lamp and sensors must be calibrated at least every 500 h of operation. Calibration includes:
- Irradiance sensor check with a reference radiometer.
- Black standard thermometer calibration against a certified thermometer.
- Humidity sensor verification using a psychrometer or a standard salt‑solution reference.
Warning: Inaccurate calibration of the irradiance sensor is a major source of inter‑laboratory variability. Perform calibration at the beginning of each test series and whenever the lamp is replaced.
Compliance and Reporting
To demonstrate compliance with CAN CGSB 4.2 No. 73.4-M91 (2013), the test report must include:
- Reference to this standard.
- Description of apparatus and filters used.
- Method, exposure conditions, and any deviations.
- Blue wool references used and their rating.
- Change in colour (ΔE) and final lightfastness rating.
Success: When the test is performed strictly as described, the method yields reproducible results suitable for certification and quality control. Many Canadian retailers and regulators accept reports based on this standard as part of product compliance.
Danger: Never look directly at the operating xenon arc lamp. Protective UV‑blocking eyewear must be worn. Ensure the instrument housing is properly interlocked to prevent accidental exposure to intense UV radiation.
Frequently Asked Questions
Q: What is the difference between CAN CGSB 4.2 No. 73.4-M91 (2013) and ISO 105-B02?
A: CAN CGSB 4.2 No. 73.4 is technically equivalent to ISO 105-B02:1994 but includes specific modifications for Canadian climatic conditions, such as tighter tolerances on humidity and temperature during testing.
A: CAN CGSB 4.2 No. 73.4 is technically equivalent to ISO 105-B02:1994 but includes specific modifications for Canadian climatic conditions, such as tighter tolerances on humidity and temperature during testing.
Q: How long does a test usually take?
A: The exposure duration depends on the required lightfastness rating. For a rating of 3, the test may be completed in about 20 h; for ratings of 7–8, the test can exceed 100 h of continuous exposure.
A: The exposure duration depends on the required lightfastness rating. For a rating of 3, the test may be completed in about 20 h; for ratings of 7–8, the test can exceed 100 h of continuous exposure.
Q: Can this standard be used for materials other than textiles?
A: While it is written specifically for textiles, the same xenon arc method can be adapted for other flexible materials, provided the sample holder and conditioning requirements are met. However, official certification for non‑textiles typically requires a specific standard (e.g., ASTM or ISO for plastics or coatings).
A: While it is written specifically for textiles, the same xenon arc method can be adapted for other flexible materials, provided the sample holder and conditioning requirements are met. However, official certification for non‑textiles typically requires a specific standard (e.g., ASTM or ISO for plastics or coatings).
Q: Is the 2013 reaffirmation still current?
A: Yes, as of 2026 the standard remains a valid CGSB document. Users should always check the CGSB website for any amendments or newer editions.
A: Yes, as of 2026 the standard remains a valid CGSB document. Users should always check the CGSB website for any amendments or newer editions.
Last updated: 2026. For official copies, contact the Canadian General Standards Board or authorized distributors.