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CAN CGSB 4.2 No. 72.3-M91 (2013): Standard Test Method for Colourfastness to Light of Textiles Using a Xenon Arc Lamp
A comprehensive guide to the Canadian standard for assessing lightfastness of coloured textiles under simulated sunlight exposure.
Scope and Application
CAN CGSB 4.2 No. 72.3-M91 (2013), reaffirmed in 2013, is a Canadian national standard developed by the Canadian General Standards Board (CGSB) that specifies a test method for determining the colourfastness of textiles to the action of artificial light emitted by a xenon arc lamp. The method is intended to simulate the photochemical effects of natural daylight, including the ultraviolet and visible parts of the solar spectrum, under controlled laboratory conditions.
The standard applies to all types of textile materials — natural, synthetic, dyed, printed, or otherwise coloured — in the form of fabrics, yarns, fibres, or end products. It is widely used in quality control, product development, and compliance testing within the Canadian textile and apparel industry. The test yields a numerical lightfastness rating (from 1 – very poor to 8 – outstanding) by comparing fade of the specimen to that of reference blue wool standards exposed simultaneously.
Intended Use: This test method is particularly relevant for textile producers exporting to Canada or complying with Canadian procurement specifications. It provides a reliable and reproducible assessment of colour stability under indoor and outdoor light exposure.
Technical Requirements
Apparatus and Materials
The standard calls for a xenon arc fading apparatus equipped with appropriate filters to simulate daylight (typically a combination of borosilicate and soda lime glass). Key components include:
- Light Source: A water-cooled or air-cooled xenon arc lamp with a spectral power distribution conforming to specified tolerances.
- Black Standard Thermometer (BST): To measure the maximum specimen surface temperature, typically maintained at 50 ± 2°C.
- Humidity and Temperature Control: The chamber must maintain a relative humidity of 40 ± 5% and an ambient air temperature of 40 ± 2°C.
- Specimen Holders: Rigid frames that hold specimens flat against a backing material (cardboard or metal) to ensure uniform exposure.
- Reference Blue Wool Standards: Eight standards (L2 to L9) each with known lightfastness ratings, used as internal reference points.
The following table summarises the principal test conditions prescribed by the standard.
| Parameter | Specification |
|---|---|
| Irradiance (at 420 nm) | 1.10 ± 0.03 W/m² |
| Black Standard Temperature | 50 ± 2 °C |
| Chamber Air Temperature | 40 ± 2 °C |
| Relative Humidity | 40 ± 5 % |
| Exposure Cycle | Continuous light or alternating light/dark (optional) |
| Standard Exposure Duration | Until the reference blue wool (L4) shows a colour change equal to Grey Scale 4 (typically 10–20 h) |
Specimen Preparation
Specimens are cut to standard dimensions (e.g., 100 mm × 40 mm) and mounted on the specimen holder with a white, non‑fluorescent backing. At least one specimen per sample is tested, and duplicates are recommended. For textured or pile fabrics, care is taken to align nap direction uniformly.
Exposure and Evaluation
The specimens and blue wool references are exposed side‑by‑side under the same conditions. The exposure cycle may be continuous or include dark phases to simulate night‑time conditions if required. After exposure, colour change is assessed visually using the Grey Scale for Colour Change (ISO 105‑A02). The degree of fading of the test specimen is compared to that of the blue wool references exposed for identical durations. The lightfastness rating is taken as the number of the blue wool standard that shows a comparable colour change, or a half‑step grade if fading falls between two references.
Key Tip: For accurate grading, use fresh blue wool references from a certified supplier and replace them according to the manufacturer’s expiry date. The latent fade of older references may skew results.
Implementation Highlights
To achieve consistent results when implementing CAN CGSB 4.2 No. 72.3-M91 (2013), laboratories must pay attention to the following aspects:
- Calibration of Apparatus: The xenon arc irradiance, temperature sensors (BST), and humidity sensors should be calibrated at regular intervals using traceable reference instruments. Many laboratories schedule calibration every 500 operating hours or quarterly, whichever comes first.
- Xenon Lamp Replacement: Lamps typically require replacement after 1500–2000 hours of use, or when irradiance output falls outside the tolerance window.
- Filter Maintenance: Glass filters degrade in transmission over time; replace them per the manufacturer’s instructions (often every 2000–3000 hours).
- Specimen Mounting: Avoid stretching or distorting the specimen. Use a fresh piece of backing board for each test to prevent contamination from previous samples.
- Environmental Control: Monitor chamber conditions continuously; deviations beyond tolerances require aborting the test and re‑running.
Important Consideration: Always run a set of blue wool references with each test batch. They serve as an internal control and ensure that any change in the equipment’s performance is captured in the evaluation.
Larger laboratories often automate exposure and grading using spectrophotometers; the standard permits instrumental measurement of colour change as an alternative to visual assessment, provided the instrument is calibrated against the Grey Scale. This can improve repeatability, especially for borderline ratings.
Compliance and Practical Notes
CAN CGSB 4.2 No. 72.3-M91 (2013) is referenced in various Canadian government procurement documents (e.g., for uniforms, technical textiles, and protective clothing). While not a mandatory regulation, demonstrating compliance with this standard is often a contractual requirement. A lightfastness rating of 4 or higher is typically acceptable for most apparel applications, while outdoor or automotive textiles may require ratings of 6 or better.
- Interlaboratory Variability: Factors such as differences in lamp aging, filter condition, and grading practice can cause variation. Participation in proficiency testing programmes is recommended.
- Relation to Other Standards: The test method is technically equivalent to ISO 105‑B02 (Colourfastness to artificial light: Xenon arc fading lamp test) but contains specific notes and tolerances adopted by CGSB. Users familiar with ISO 105‑B02 will find the procedures very similar. However, for Canadian regulatory or customer specifications, the CGSB version must be followed.
- Record Keeping: Retain exposure records, calibration certificates, and test reports for at least three years to support audits or product claims.
Common Pitfall: Using an incorrect filter combination (e.g., only borosilicate without soda lime) changes the UV cut‑off and can lead to unrealistic fading, especially for UV‑sensitive dyes. Always verify that the apparatus is configured as required by the standard.
Q: Is CAN CGSB 4.2 No. 72.3-M91 (2013) identical to ISO 105‑B02?
A: They are technically equivalent in most respects, but the CGSB standard includes slightly different tolerances for some exposure parameters and is the accepted version for Canadian markets and procurement. It is recommended to consult the specific contractual requirement to determine which version to use.
A: They are technically equivalent in most respects, but the CGSB standard includes slightly different tolerances for some exposure parameters and is the accepted version for Canadian markets and procurement. It is recommended to consult the specific contractual requirement to determine which version to use.
Q: Can this standard be used for automotive interior textiles?
A: For automotive applications, more severe exposure conditions (higher irradiance, higher BST) are often required, as specified in SAE J2412 or other automotive standards. CAN CGSB 4.2 No. 72.3 is intended for general textiles; however, it can be adapted if agreed between parties, but dedicated automotive standards are preferred.
A: For automotive applications, more severe exposure conditions (higher irradiance, higher BST) are often required, as specified in SAE J2412 or other automotive standards. CAN CGSB 4.2 No. 72.3 is intended for general textiles; however, it can be adapted if agreed between parties, but dedicated automotive standards are preferred.
Q: How often should the xenon arc lamp be replaced?
A: Replacement is recommended after 1500–2000 hours of operation or when the irradiance at 420 nm falls below 1.07 W/m² under normal conditions. Always follow the instrument manufacturer’s guidelines and perform a validation test with blue wool references after each lamp change.
A: Replacement is recommended after 1500–2000 hours of operation or when the irradiance at 420 nm falls below 1.07 W/m² under normal conditions. Always follow the instrument manufacturer’s guidelines and perform a validation test with blue wool references after each lamp change.
Q: What does a lightfastness rating of 4 mean?
A: A rating of 4 on the 1–8 scale indicates moderate lightfastness. The specimen’s colour change is similar to that of blue wool standard L4. For most indoor textile applications, a rating of 4 is acceptable, but for long‑term display or outdoor use, a rating of 6 or higher is recommended.
A: A rating of 4 on the 1–8 scale indicates moderate lightfastness. The specimen’s colour change is similar to that of blue wool standard L4. For most indoor textile applications, a rating of 4 is acceptable, but for long‑term display or outdoor use, a rating of 6 or higher is recommended.
Document reference year: 2026. This article is for informational purposes and does not replace the full text of the standard. Always refer to the official CGSB publication for definitive requirements.