CAN CGSB 4.2 No. 69-M91 (2013): Colourfastness to Light Testing of Automotive Textiles

Scope and Purpose

CAN CGSB 4.2 No. 69-M91 (2013) – formally titled Textile Test Methods – Colourfastness to Light: High Temperature Light Exposure Test for Automotive Fabrics – is a Canadian national standard developed by the Canadian General Standards Board (CGSB). It specifies a test method for evaluating the resistance of textile colour to the combined effect of light and high temperature, conditions that are specifically representative of automotive interior environments. The method is applicable to all types of textiles used in vehicle cabins, including woven, knitted, nonwoven, and coated fabrics, as well as tufted carpets.

The primary purpose of this standard is to simulate the prolonged exposure of interior textiles to sunlight through window glass while subjected to the elevated temperatures that can occur inside a closed vehicle. Unlike conventional room-temperature lightfastness tests, this method imposes a more rigorous thermal load to better predict real-world fading performance. The standard was originally published in 1991 and reaffirmed in 2013, confirming its continued relevance for automotive material qualification and quality control.

Technical Requirements and Test Procedure

Test Apparatus

The standard requires a xenon-arc lightfastness tester equipped with an optical filter system that simulates sunlight passing through automotive window glass (i.e., window-glass filter). The equipment must be able to maintain controlled conditions of irradiance, black panel temperature, chamber temperature, and relative humidity. A black panel thermometer is used to measure the temperature at the specimen surface, while a humidity sensor monitors the chamber atmosphere.

Exposure Conditions

CAN CGSB 4.2 No. 69-M91 (2013) defines two alternative exposure methods (A and B) that differ primarily in the black panel temperature and humidity settings. Method A applies a slightly higher temperature and lower humidity, while Method B uses a moderate temperature with controlled humidity. Table 1 summarises the mandatory conditions.

The choice between methods is typically dictated by the end-use climate conditions or customer specification. For most Canadian automotive applications, Method A is preferred due to its closer simulation of severe summer dashboard temperatures.

Specimen Preparation and Mounting

Test specimens are cut to the dimensions required by the instrument specimen holder, typically at least 45 mm × 120 mm. The reverse side of each specimen is covered with a white backing material (e.g., a specified cotton or polyester fabric) to prevent contamination of the instrument and to simulate typical interior substrate conditions. Four or more replicate specimens are usually prepared, along with a set of blue wool reference standards (grades L2 to L9).

Exposure and Evaluation

Specimens and blue wool references are mounted on a rotating drum inside the xenon-arc chamber and exposed for a predetermined duration or until the reference standards exhibit a specified colour change. The standard uses two evaluation methods:

• Visual assessment – comparison of the exposed specimen to the original unexposed material using the ISO grey scale for colour change (ISO 105-A02).
• Blue wool rating – the lightfastness grade is reported as the number of the blue wool standard that shows a colour change equivalent to that of the test specimen. Typical ratings range from 2 (very low) to 8 (very high). For automotive interior fabrics, a minimum rating of 5 (L5) or 6 (L6) is often required.

Implementation in Textile Quality Assurance

Adopting CAN CGSB 4.2 No. 69-M91 (2013) within a textile testing laboratory requires careful attention to equipment, training, and procedures. The following highlights are critical for successful implementation.

Equipment Calibration and Maintenance

Xenon-arc testers must be maintained according to the manufacturer’s instructions and calibrated at least every 500 hours of operation or annually, whichever comes first. Calibration verifies irradiance uniformity, black panel temperature accuracy, and humidity sensor performance. Radiometer filters should be replaced as recommended to avoid spectral drift.

Operator Training

Personnel performing the test must be trained in specimen mounting techniques, interpretation of grey scale and blue wool references, and detection of anomalies such as non-uniform fading or condensation. Retraining is recommended when test parameters are changed or after long equipment downtime.

Interlaboratory Reproducibility

Although the standard is precise, variations can occur between different laboratories due to differences in instrument design, filter age, and ambient conditions. Participation in proficiency testing programmes (e.g., those organised by CGSB or ASTM) is encouraged to benchmark performance and identify systematic errors.

Compliance and Interpretation of Results

The results of the test are used to determine whether a textile product meets the lightfastness specification of the end user. As CAN CGSB 4.2 No. 69-M91 (2013) is a test method standard rather than a product standard, it does not itself specify pass/fail criteria; these are established by the purchasing party or by other applicable documents (e.g., OEM material specifications, generic quality standards such as SAE J1885 or ISO 105-B06).

Reporting

The test report should include, at a minimum:

• Standard number and year (CAN CGSB 4.2 No. 69-M91 (2013));
• Exposure method (A or B);
• Black panel temperature and humidity measured during the test;
• Total exposure duration or radiant exposure (in kJ/m² at 300–400 nm);
• Blue wool reference grades used and the rating assigned to the specimen;
• Any deviations from the standard procedure (e.g., backing material substitution);
• Date of test and identification of the testing laboratory.

Common Non-Conformances

When results fail to meet requirements, common causes include: inadequate dye selection for high-temperature stability, migration of plasticisers or finishes from backing materials, uneven exposure due to poor specimen mounting, or use of filters that do not match the specified window-glass spectral distribution. Before rejecting a material, a second test with a fresh specimen set is recommended.

Table 2: Blue Wool Reference System – Colourfastness Grades

Frequently Asked Questions