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CAN CGSB 4.2 No. 26.1-M88 (2013): Colourfastness to Light Testing of Textiles – Xenon Arc Method
Comprehensive Guide to the Canadian Standard for Assessing Textile Colourfastness Under Artificial Light
Introduction
CAN CGSB 4.2 No. 26.1-M88 (2013), part of the Canadian General Standards Board (CGSB) textile test methods series, specifies a method for determining the colourfastness of textiles to artificial light using a xenon arc lamp. This standard is essential for evaluating the resistance of dyed or printed textiles to fading when exposed to simulated sunlight, ensuring product quality and consumer satisfaction. It is widely referenced by manufacturers, testing laboratories, and regulatory bodies across Canada and internationally.
Scope and Purpose
The standard outlines a procedure for assessing the change in colour of textiles after exposure to light under controlled conditions. It is applicable to all forms of textile materials—natural, synthetic, or blends—regardless of whether they are dyed, printed, or otherwise coloured. The method uses a xenon arc lamp that closely mimics the spectral distribution of natural daylight, particularly in the ultraviolet (UV) region, to accelerate fading tests. Results are expressed using grey scales and blue wool reference standards.
Note: This standard is technically equivalent to ISO 105-B02, facilitating international harmonisation of colourfastness testing.
Technical Requirements and Test Methods
Test Principle
Specimens of the textile material are exposed to light from a xenon arc lamp along with a set of blue wool reference standards under specified conditions of temperature, humidity, and irradiance. The colour change of the specimen is assessed after a defined exposure period, either by comparison with the reference standards or by using a grey scale for colour change.
Apparatus
The key apparatus includes:
- Xenon arc lamp system – equipped with appropriate filters to simulate daylight (e.g., borosilicate filters for UV cut-off).
- Sample holders – capable of exposing specimens and reference standards simultaneously.
- Black standard thermometer – to monitor the surface temperature (typically 45°C ± 3°C).
- Humidity control – relative humidity at 40% ± 5% or 60% ± 5%, depending on the test cycle.
- Radiometer – to measure irradiance at 420 nm (typically 1.1 W/m²·nm).
| Parameter | Condition (Standard Cycle) | Tolerance |
|---|---|---|
| Black standard temperature | 45 °C | ± 3 °C |
| Relative humidity | 40% or 60% | ± 5% |
| Irradiance (at 420 nm) | 1.10 W/(m²·nm) | ± 0.03 W/(m²·nm) |
| Exposure duration | As needed to reach 20 AFU | – |
Blue Wool Reference Standards
The standard specifies eight blue wool references (grades 1–8) that fade at different rates. Grade 1 fades the fastest, grade 8 the slowest. These are used to calibrate exposure levels and to assign colourfastness ratings.
| Blue Wool Grade | Fading Characteristics | Lightfastness Scale |
|---|---|---|
| 1 | Very low colourfastness | 1 |
| 2 | Low colourfastness | 2 |
| 3 | Moderately low | 3 |
| 4 | Moderate | 4 |
| 5 | Moderately high | 5 |
| 6 | High | 6 |
| 7 | Very high | 7 |
| 8 | Extremely high | 8 |
Assessment
Two methods of assessment are permitted:
- Method 1: Expose the specimen simultaneously with the blue wool standards and use the grey scale to assess colour change. The rating is assigned as the number of the blue wool that shows a similar change.
- Method 2: For routine control, expose only the test specimen and use the blue wool to determine exposure duration. The colour change is assessed using the grey scale.
Best Practice Tip: For accreditation purposes, use Method 1 as it provides a direct comparison with traceable reference materials and aligns with ISO requirements.
Implementation Highlights
Calibration and Maintenance
Regular calibration of the radiometer and black standard thermometer is critical. The irradiance sensor must be recalibrated annually or after every 2000 hours of lamp use. The xenon lamp itself typically requires replacement after 1500 hours.
Specimen Preparation
Cut specimens to dimensions that fit the sample holder (commonly 45 mm × 100 mm). Condition them in a standard atmosphere (21°C, 65% RH) for 24 hours before testing. Avoid touching the test area with bare hands. If measuring colourchange using a spectrophotometer, the standard aperture size must be used.
Interpreting Results
| Rating | Meaning | Typical Application |
|---|---|---|
| 8–7 | Excellent lightfastness | Automotive interior textiles, outdoor fabrics |
| 6–5 | Good lightfastness | Apparel, home textiles (curtains, upholstery) |
| 4–3 | Fair to poor lightfastness | Disposable or limited‑use items |
| 2–1 | Very poor lightfastness | Not suitable for prolonged daylight exposure |
Common Pitfall: Failing to control humidity during the light cycle can cause inaccurate fading. For blue wool 4 (grade 4), a change in RH of 10% can shift the fading rate by up to two days of equivalent exposure.
Compliance Notes
Accreditation
Laboratories performing this test for certification or regulatory purposes should be accredited to ISO/IEC 17025 by a recognized body (e.g., SCC, A2LA). Records of calibration, environmental conditions, and operator training must be maintained.
Reporting
Test reports should include:
- Reference to CAN CGSB 4.2 No. 26.1-M88 (2013)
- Type of xenon arc lamp (air‑cooled or water‑cooled)
- Irradiance level and wavelength
- Temperature and humidity during exposure
- Blue wool grade(s) used and method of assessment
- Colourfastness rating and exposure duration (in AFU)
Limitations
The standard does not cover exposure to outdoor weathering (natural or accelerated). For combined light and weather resistance, refer to CAN CGSB 4.2 No. 26.3. Also, fluorescent brightening agents may complicate interpretation; additional reference standards should be considered.
Non‑Compliance Risk: Inconsistent test conditions—such as uncalibrated irradiance or temperature drift—can lead to false pass/fail results, potentially causing costly product recalls or warranty claims.
Compliance Benefit: Adhering strictly to this standard yields reproducible, defensible colourfastness data, supporting product claims and regulatory acceptance in the Canadian market and beyond.
Frequently Asked Questions
Q: Is CAN CGSB 4.2 No. 26.1-M88 (2013) identical to ISO 105-B02?
A: The two standards are technically equivalent. However, minor editorial differences exist in the preamble and the specific calibration procedures. Laboratories that comply with one may need a gap analysis to fully meet the other. It is recommended to consult both standards when seeking dual accreditation.
A: The two standards are technically equivalent. However, minor editorial differences exist in the preamble and the specific calibration procedures. Laboratories that comply with one may need a gap analysis to fully meet the other. It is recommended to consult both standards when seeking dual accreditation.
Q: How often should the xenon arc lamp be replaced?
A: The lamp should be replaced after 1500 hours of operation or when the irradiance sensor indicates a drop below 80% of its initial value at 420 nm. Always replace with a lamp meeting the spectral output specifications of the instrument manufacturer.
A: The lamp should be replaced after 1500 hours of operation or when the irradiance sensor indicates a drop below 80% of its initial value at 420 nm. Always replace with a lamp meeting the spectral output specifications of the instrument manufacturer.
Q: Can I use the same blue wool references indefinitely?
A: No. Blue wool references are consumables. Each set of blue wool standards is calibrated by the manufacturer and should be discarded after use or after a defined shelf life (typically 5 years from the date of certification). Once exposed, they cannot be reused for quantitative ratings.
A: No. Blue wool references are consumables. Each set of blue wool standards is calibrated by the manufacturer and should be discarded after use or after a defined shelf life (typically 5 years from the date of certification). Once exposed, they cannot be reused for quantitative ratings.
Q: Does the standard apply to non‑textile substrates such as paper or leather?
A: The standard is specifically written for textiles. While the principles may be adapted for other materials, the user should verify that the apparatus conditions and assessment criteria are appropriate. For paper, refer to ISO 9705; for leather, to IULTCS/IUF 402 or similar.
A: The standard is specifically written for textiles. While the principles may be adapted for other materials, the user should verify that the apparatus conditions and assessment criteria are appropriate. For paper, refer to ISO 9705; for leather, to IULTCS/IUF 402 or similar.
This article reflects the standard as reaffirmed in 2013 and incorporates industry best practices as of 2026.