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CAN CGSB 4.2 No. 73.1-M91 (2013): Xenon Arc Colour Fastness Testing for Textiles
Comprehensive Guide to the Canadian Standard for Lightfastness Assessment
Scope and Introduction
CAN CGSB 4.2 No. 73.1-M91 (2013) is a test method issued by the Canadian General Standards Board (CGSB) and is part of the CGSB 4.2 series of standard test methods for textiles. This standard specifies a procedure for determining the colour fastness of textile materials of all kinds (including fibres, yarns, and fabrics) to the action of artificial light. The method employs a xenon arc lamp as the light source, which closely simulates natural daylight, including the ultraviolet (UV) region.
The standard was originally published as ‘M91’ in 1991 and reaffirmed in 2013, confirming its continued technical relevance. It is technically equivalent to ISO 105-B02 but is tailored for Canadian regulatory and industrial contexts. Laboratories seeking accreditation for textile testing in Canada or exporting goods requiring lightfastness assurance must be familiar with this standard.
Technical Requirements
Test Apparatus
The central apparatus is a xenon-arc fading lamp system, which must meet the following specifications:
- Light source: Xenon arc lamp with filters to simulate daylight (e.g., borosilicate glass for improved UV simulation).
- Irradiance control: Capability to maintain a specified irradiance level, typically 42 W/m² in the wavelength range 300–400 nm.
- Temperature and humidity control: The test chamber must maintain a specified black standard temperature (BST) and relative humidity (RH).
- Specimen holders: Rotating or stationary racks that ensure uniform exposure across all test specimens and reference materials (blue wool standards).
Test Specimens and Reference Materials
Specimens are prepared according to the product specification or agreement between parties. Typically, specimens are cut to fit the specimen holder (e.g., 45 x 120 mm). The method requires the use of Blue Wool Lightfastness Standards (grades 1 to 8) as references to assess the amount of light exposure. The specimen and reference standards are exposed simultaneously under controlled conditions.
Exposure Conditions
The standard defines several exposure options based on the intended end-use environment. Below is a summary of key parameters:
| Parameter | Option 1 (Mild) | Option 2 (Severe) |
|---|---|---|
| Black Standard Temperature (°C) | 50 ± 2 | 65 ± 2 |
| Relative Humidity (%) | 40 ± 5 | 60 ± 5 |
| Irradiance (W/m² @ 300–400 nm) | 42 | 42 |
| Inner/Outer Filter | Borosilicate | Borosilicate |
| Duration (hours) | Variable (until reference fades) | Variable (until reference fades) |
Note: The actual duration is determined by comparing the fading of the blue wool standard(s) to a defined rating.
Implementation Highlights
Procedure
- Preparation: Condition specimens and blue wool standards in a standard atmosphere (21 °C, 65 % RH) for 24 hours.
- Mounting: Mount specimens and references on the exposure device, ensuring shading or tripping is avoided.
- Exposure: Start the xenon arc lamp and adjust to the required irradiance, temperature, and humidity. Expose until the reference blue wool standard exhibits a specific contrast (e.g., grade 4 fading).
- Assessment: Remove specimens and evaluate colour change using the Grey Scale for Colour Change (ISO 105-A02) or evaluate against the fading of the blue wool reference.
Interpretation of Results
The lightfastness rating is assigned based on the comparison of the specimen’s colour change to the reference blue wool standards. Ratings range from 1 (very poor) to 8 (excellent). The test report must include the exposure conditions, the blue wool standard used for assessment, and the final rating.
Tip: For consistent results, always position specimens and blue wool references in the same area of the exposure chamber and rotate holders periodically to compensate for any spatial variations in irradiance.
Warning: Drift in relative humidity is a common source of error. Use a dedicated hygrometer and servomechanism to maintain RH within ±5 % of the set point.
Best Practice: Align your internal procedure with CAN CGSB 4.2 No. 73.1-M91 (2013) to ensure test results are recognized by Canadian regulatory bodies and major retailers requiring lightfastness data.
Critical: Never operate the xenon lamp without proper filters; exposure to unfiltered UV can cause rapid, unrealistic fading and invalidate the test. Replace filters according to the manufacturer’s recommended schedule.
Compliance and Quality Assurance
Accreditation
To perform testing to this standard, laboratories should be accredited by a recognized body (e.g., Standards Council of Canada, SCC). This ensures the laboratory meets ISO/IEC 17025 requirements and has demonstrated proficiency in lightfastness testing.
Instrument Calibration
Regular calibration of the xenon arc system is mandatory. This includes:
- Radiometer calibration against a reference radiometer traceable to a national standard.
- Periodic checks of black standard temperature sensors and humidity probes.
- Verification of the spectral distribution using a spectroradiometer at least annually.
Test Report Requirements
The test report should include:
- Reference to CAN CGSB 4.2 No. 73.1-M91 (2013).
- Exposure conditions (temperature, humidity, irradiance, filters).
- Blue wool standard used and the level of fading at assessment.
- Lightfastness rating and the grey scale assessment if applicable.
- Any deviations from the standard method.
Q: How does CAN CGSB 4.2 No. 73.1-M91 (2013) relate to ISO 105-B02?
A: The two standards are technically equivalent in test principles and equipment. CAN CGSB 4.2 No. 73.1 is the Canadian adoption, and compliance is often interchangeable. However, exporters should check if a specific standard is required by the destination market.
A: The two standards are technically equivalent in test principles and equipment. CAN CGSB 4.2 No. 73.1 is the Canadian adoption, and compliance is often interchangeable. However, exporters should check if a specific standard is required by the destination market.
Q: Can this method be applied to leather and coated fabrics?
A: Yes, the method covers all forms of textile materials. However, care must be taken in specimen mounting to avoid distortion or delamination during exposure.
A: Yes, the method covers all forms of textile materials. However, care must be taken in specimen mounting to avoid distortion or delamination during exposure.
Q: What is the typical duration of a test to a grade 4 blue wool?
A: Under standard conditions, a grade 4 blue wool can require 20 to 40 hours of exposure, but the exact time depends on the irradiance and the specific blue wool batch. The method uses fading of the reference to define endpoint, not a fixed time.
A: Under standard conditions, a grade 4 blue wool can require 20 to 40 hours of exposure, but the exact time depends on the irradiance and the specific blue wool batch. The method uses fading of the reference to define endpoint, not a fixed time.
Last updated: 2026. This article is for informational purposes. Always refer to the latest revision of the standard for official requirements.