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CAN CGSB 4.2 No. 31-2004 (2013): Textile Test Methods – Colour Fastness to Light (Xenon Arc Lamp)
Understanding the Scope, Requirements, and Compliance for Lightfastness Testing in Textiles
Scope
CAN CGSB 4.2 No. 31-2004 (2013) Textile Test Methods – Colour Fastness to Light: Xenon Arc Lamp Method is a Canadian national standard developed by the Canadian General Standards Board (CGSB). It specifies a method for determining the resistance of the colour of textiles of all kinds to the action of an artificial light source representative of natural daylight (D65). The standard applies to all textile materials including fibres, yarns, fabrics, and finished articles, irrespective of their fibre composition or colour application method.
The test principle involves exposing textile specimens together with a set of blue wool reference standards under controlled conditions to a xenon arc lamp. After a defined exposure period, the colour change of the specimen is assessed by comparing it to the fading exhibited by the reference materials. The result is expressed as a numerical lightfastness rating on a scale from 1 (very poor) to 8 (outstanding).
This standard is technically equivalent to ISO 105-B02 and aligns with AATCC TM 16.3, though specific conditioning and reporting requirements may differ. It is widely used in Canadian textile manufacturing, retail, and regulatory compliance for apparel, home furnishings, and technical textiles.
Technical Requirements
Apparatus and Instrumentation
The standard mandates the use of a xenon arc lamp capable of simulating natural daylight, equipped with appropriate filters (borosilicate or soda lime glass) to achieve the specified spectral distribution. Key apparatus parameters include:
- Irradiance: Controlled at 1.10 ± 0.03 W/(m²·nm) at 420 nm, or equivalent broadband setting.
- Black Standard Temperature (BST): 50–55 °C for moderate conditions; up to 65 °C for extreme conditions.
- Chamber Air Temperature: 30–35 °C.
- Relative Humidity: 35 ± 5% for low humidity cycles; 60 ± 5% for high humidity cycles.
Reference Materials and Scale
Blue wool references (BS 1006:UK-TOU or ISO 105-B01/B02) are used as the calibrating scale. Each of the eight blue wool fabrics (grades 1–8) has a known fading rate. The test specimen’s colour change is matched to the reference that shows the same amount of fading. The Lightfastness Rating is then assigned accordingly.
| Blue Wool Grade | Description | Lightfastness Rating |
|---|---|---|
| 1 | Very low fastness | 1 |
| 2–3 | Low fastness | 2–3 |
| 4–5 | Moderate fastness | 4–5 |
| 6–7 | High fastness | 6–7 |
| 8 | Outstanding fastness | 8 |
Implementation Highlights
Successful implementation of CAN CGSB 4.2 No. 31-2004 (2013) requires meticulous attention to specimen preparation and instrument calibration.
- Specimen Preparation: Test specimens must be cut to a minimum size of 40 mm × 40 mm and conditioned at 21 ± 1 °C and 65 ± 2% RH for at least 4 hours prior to testing. Each specimen is mounted on an opaque backing card with the face exposed. The blue wool references are mounted adjacent to the specimens in the exposure frame.
- Exposure Cycle: The xenon arc lamp is run continuously, with provisions for a dark cycle if required. The standard specifies exposure intervals based on the expected lightfastness. At the end of the exposure, the specimen is compared to its unexposed portion using the grey scale for colour change (e.g., ISO 105-A02 or AATCC Evaluation Procedure 1). The number of hours required to produce a specific contrast (e.g., Step 4 grey scale) is recorded.
- Interim Assessments: For materials that fade rapidly, observations are made at shorter intervals. The final rating is obtained when the fading of the best blue wool reference that shows a “just noticeable” change matches the change observed in the specimen.
Tip: Ensure the xenon lamp is properly seasoned (≥250 hours) and that optical filters are replaced every 1000 operating hours to maintain spectral accuracy. Regularly verify irradiance uniformity with a calibrated radiometer.
Data Reporting
Each test report must include:
- Standard designation and year (CAN CGSB 4.2 No. 31-2004 (2013)).
- Apparatus make, model, and filter type.
- Exposure conditions: irradiance, temperature, humidity.
- Blue wool series and batch number.
- Lightfastness rating (1–8) or number of exposure hours to reach specific contrast.
Compliance Notes
CAN CGSB 4.2 No. 31-2004 (2013) is a voluntary consensus standard in Canada; however, it is often invoked by retailers, government procurement agencies, and regulatory bodies (e.g., Canada Consumer Product Safety Act compliance for children’s sleepwear). Testing according to this standard is accepted as evidence of due diligence for colour fastness claims.
Compliance advantage: Products meeting a lightfastness rating of 4 or higher are generally considered suitable for apparel and interior textiles where moderate light exposure is expected. A rating of 6 or higher is recommended for automotive textiles and outdoor fabrics.
Key compliance considerations:
- Laboratories must participate in proficiency testing programs (e.g., CGSB interlaboratory studies) to maintain accreditation.
- When disputes arise, the referee method uses the blue wool scale rather than instrumental evaluation.
- If a product fails the required rating, mitigation options include dye selection modification, use of UV absorbers, or addition of anti‑oxidants.
Warning: Do not substitute this standard with ISO 105-B02 without confirming that the selected humidity and temperature conditions match the intended end‑use environment. In Canada, interior applications often require the moderate humidity cycle (35% RH) rather than the maritime cycle (60% RH).
Non-compliance risk: Relying on unaccredited lab reports or expired bulb calibrations can lead to false pass results. A product that fades prematurely can result in customer returns, brand reputation damage, and potential regulatory action if safety labelling (e.g., fire retardant coatings) degrades along with colour.
Frequently Asked Questions
Q: What is the difference between CAN CGSB 4.2 No. 31-2004 (2013) and ISO 105-B02?
A: The two standards are technically equivalent in test principle and apparatus. However, CAN CGSB 4.2 No. 31 includes specific conditioning requirements (21 °C, 65% RH) and references Canadian blue wool supply sources. It also offers three humidity options (low, moderate, high) tailored to typical North American climate zones.
A: The two standards are technically equivalent in test principle and apparatus. However, CAN CGSB 4.2 No. 31 includes specific conditioning requirements (21 °C, 65% RH) and references Canadian blue wool supply sources. It also offers three humidity options (low, moderate, high) tailored to typical North American climate zones.
Q: Is the standard still current if its year is 2004?
A: Yes, the standard was reaffirmed in 2013, meaning no technical changes were made but it remains an active CGSB standard. Users should check CGSB’s website for any amendments or revisions.
A: Yes, the standard was reaffirmed in 2013, meaning no technical changes were made but it remains an active CGSB standard. Users should check CGSB’s website for any amendments or revisions.
Q: Can I use instrumental colour measurement instead of visual grey scale assessment?
A: The standard allows instrumental evaluation (colorimetry using CIELAB ΔE*) as an alternative for final rating when agreed upon between parties, but the blue wool visual method remains the referee method in case of dispute.
A: The standard allows instrumental evaluation (colorimetry using CIELAB ΔE*) as an alternative for final rating when agreed upon between parties, but the blue wool visual method remains the referee method in case of dispute.
Q: What lightfastness rating is required for upholstery fabrics under Canadian interior standards?
A: For general interior fabrics, a minimum rating of 4 (moderate) is typical; for contract textiles (e.g., health care, education), a rating of ≥5 is often specified. Automotive fabrics generally require rating 7 or 8.
A: For general interior fabrics, a minimum rating of 4 (moderate) is typical; for contract textiles (e.g., health care, education), a rating of ≥5 is often specified. Automotive fabrics generally require rating 7 or 8.