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CAN CGSB 4.2 No. 65-M91 (2013): Colourfastness to Light Testing of Textiles with Xenon Arc Lamp
A comprehensive guide to the scope, technical requirements, implementation, and compliance of the CGSB standard for lightfastness assessment
Technical Scope: This standard is harmonized with ISO 105-B02 and specifies a test method for determining the resistance of textile colours to the action of artificial light (xenon arc lamp) simulating natural daylight.
1. Scope and General Overview
CAN CGSB 4.2 No. 65-M91 (2013) is a national standard of Canada developed by the Canadian General Standards Board (CGSB). It is part of the CGSB 4.2 series of textile test methods. This standard outlines a procedure for assessing the colourfastness of textiles to light using a xenon arc lamp as the light source. The method is applicable to all textiles, including dyed, printed, or otherwise coloured materials, irrespective of their fibre composition or structure.
The standard describes two principal exposure techniques: the use of a blue wool reference (EU-type) and the use of a lightfastness scale (blue scale) for rating. The method can be performed with or without controlled humidity conditions, depending on the requirements. The xenon arc lamp is chosen because its spectral power distribution closely matches natural daylight, especially after proper filtering.
Important: While CAN CGSB 4.2 No. 65-M91 (2013) was reaffirmed in 2013, users should verify with the latest revision (e.g., ISO 105-B02:2014+Amd1) for international harmonization. The standard does not supersede mandatory Canadian regulations, such as those under the Textile Labelling Act.
2. Technical Requirements and Test Conditions
2.1 Apparatus and Light Source
The core apparatus is a water-cooled or air-cooled xenon arc lamp equipped with filters to simulate daylight. The standard specifies the following key parameters:
| Parameter | Requirement |
|---|---|
| Irradiance (at 420 nm) | 1.10 W/m²/nm ± 0.05 (typical setting) |
| Black Panel Temperature (BPT) | 65 °C ± 3 °C (in controlled humidity mode) |
| Chamber Temperature | 55 °C ± 3 °C (dry bulb) |
| Relative Humidity (if controlled) | 50% ± 5% |
| Cycle Duration | Continuous light or light + dark (depending on method) |
2.2 Test Specimens and Blue Wool Standards
Specimens are cut to a size that fits the sample holder (commonly 100 mm × 50 mm). A set of Blue Wool Standards (EU-style or US-style) is mounted adjacent to the test specimens on a card. The standard defines eight grades (1 = very poor, 8 = excellent) corresponding to fading steps of the blue wool references.
2.3 Exposure Procedure
The specimens and blue wool references are exposed simultaneously in the xenon arc apparatus. The exposure is continued until the contrast between exposed and unexposed portions of a particular blue wool reference reaches a defined grey scale rating (usually grade 4 of the ISO grey scale for assessing change in colour). The exposure level is reported as the number of hours to reach a specific blue wool reference fading.
Two exposure methods are allowed:
- Method A: Light exposure controlled by blue wool references – used for most general testing.
- Method B: Instrumental determination of fading – used for precision grading.
Best Practice: Always run a set of blue wool references alongside the test specimens. This allows for continuous monitoring of the light dose and compensates for any slight variations in lamp output or temperature.
3. Implementation Highlights
To implement CAN CGSB 4.2 No. 65-M91 (2013) in a laboratory setting, the following steps are critical:
- Calibration: Regularly calibrate the xenon arc lamp irradiance using a radiometer traceable to national standards. Black panel temperature sensors must be verified.
- Sample Preparation: Condition specimens in a standard atmosphere (20 °C ± 2 °C, 65% ± 4% RH) before testing. Mount each specimen on a white card to reflect unfaded colour.
- Exposure Intervals: Inspect specimens at intervals corresponding to a half-step of the blue scale (e.g., when blue wool L4 reaches a fading step equivalent to grey scale 4).
- Rating: Use the ISO 105 A02 grey scale for assessing change in colour, or a spectrophotometer if the instrumental method is chosen.
3.1 Humidity Control
When humidity control is specified, the apparatus must include a humidity sensor and a water- spraying system to maintain the relative humidity. The standard defines two methods for humidification:
- Wet method (spraying deionized water on the back of specimens).
- Conditioned air method (pre-conditioned air circulated in the chamber).
Common pitfall: Failing to pre-condition specimens to standard atmospheric moisture can lead to inaccurate fading rates. Use preconditioning for at least 4 hours before mounting.
4. Compliance Notes and Quality Assurance
4.1 Reporting Requirements
The test report must include:
- Reference to CAN CGSB 4.2 No. 65-M91 (2013).
- Description of the light source and filters used.
- Exposure conditions: black panel temperature, chamber temperature, relative humidity (if controlled).
- Blue wool reference standards used (EU or US).
- Exposure duration and method (A or B).
- Colourfastness rating (1–8) for each specimen, with intermediate half-grades permitted (e.g., 6/7).
4.2 Accreditation and Proficiency
Laboratories performing this test should be accredited to ISO/IEC 17025 to ensure competence. Participation in proficiency testing schemes (e.g., through A2LA or CCC) is highly recommended to validate results across laboratories.
Non-compliance risk: Using outdated blue wool references (e.g., older than 3 years) or erroneous exposure settings can lead to incorrect lightfastness ratings. Always check the lot number of blue wool standards for their certified fading step curves.
4.3 Relation to Other Standards
CAN CGSB 4.2 No. 65-M91 (2013) is technically equivalent to ISO 105-B02:2014 with some minor deviations in terminology. It can be used interchangeably for most product specifications. However, for automotive interiors or high-temperature applications, the SAE J1885 or ISO 105-B06 may apply. Always confirm the applicable standard with the client or regulatory body.
Frequently Asked Questions
Q: What is the difference between CAN CGSB 4.2 No. 65-M91 and ISO 105-B02?
A: The two standards are technically aligned, but CAN CGSB 4.2 No. 65-M91 includes specific notes relevant to Canadian laboratory practices, such as the use of Canadian blue wool references and preferred reporting units. The exposure method and rating scales are identical.
A: The two standards are technically aligned, but CAN CGSB 4.2 No. 65-M91 includes specific notes relevant to Canadian laboratory practices, such as the use of Canadian blue wool references and preferred reporting units. The exposure method and rating scales are identical.
Q: Do I need to use the blue wool standards every time?
A: Yes. The blue wool reference standards are mandatory for quantifying the light exposure dose. They are the only way to achieve reproducible, traceable results. Without them, the test is not compliant with the standard.
A: Yes. The blue wool reference standards are mandatory for quantifying the light exposure dose. They are the only way to achieve reproducible, traceable results. Without them, the test is not compliant with the standard.
Q: How often should I calibrate the xenon arc lamp?
A: The standard recommends calibration of irradiance at least once every 500 hours of operation, or after any lamp or filter change. Black panel temperature sensors should be verified every 3 months using a calibrated source.
A: The standard recommends calibration of irradiance at least once every 500 hours of operation, or after any lamp or filter change. Black panel temperature sensors should be verified every 3 months using a calibrated source.
Q: Can I use this standard for non-textile materials?
A: CAN CGSB 4.2 No. 65-M91 is specifically designed for textiles. For plastics, coatings, or other materials, refer to ASTM G155 or ISO 4892-2, which address xenon arc testing of plastics and coatings under similar conditions.
A: CAN CGSB 4.2 No. 65-M91 is specifically designed for textiles. For plastics, coatings, or other materials, refer to ASTM G155 or ISO 4892-2, which address xenon arc testing of plastics and coatings under similar conditions.
This article is prepared for informational purposes and reflects the standard’s status as of 2026. Always refer to the official version of CAN CGSB 4.2 No. 65-M91 (2013) for definitive procedures.