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Introduction
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Introduction
CAN CGSB 4.2 No. 55-M90 (2013) — Textile Test Methods – Colourfastness to Bleaching: Peroxide — is a Canadian national standard developed by the Canadian General Standards Board (CGSB). It specifies a method for determining the resistance of textile colour to the bleaching action of hydrogen peroxide under conditions typical of industrial bleaching processes. The standard is part of the CGSB 4.2 series, which groups more than 70 individual test methods for textile evaluation. Although originally approved in 1990 (hence the M90 designation), the standard was reaffirmed without technical change in 2013, confirming its continued relevance in quality assurance programs across Canada and internationally.
This method is technically equivalent to ISO 105-N01:1993 (Textiles — Tests for colour fastness — Part N01: Colour fastness to bleaching: peroxide). Laboratories accredited to ISO/IEC 17025 routinely adopt CAN CGSB 4.2 No. 55-M90 for testing products intended for the Canadian market or when contractually required by retailers and brands.
Scope and Application
The standard applies to all forms of textiles — fibres, yarns, and fabrics — that may be subjected to peroxide bleaching during domestic or industrial laundering. It covers both white and coloured textiles, including those that have been dyed, printed, or otherwise finished.
Tip: Peroxide bleaching is commonly encountered in textile processing stages such as scouring, brightening, and stain removal. The test is especially important for assessing whether a dye or finish can withstand repeated oxidative treatments without unacceptable shade change or staining of adjacent goods.
The method is not suitable for evaluating chlorine-based bleach fastness (which is covered by separate standards, e.g., ISO 105-N02 or CGSB 4.2 No. 56). Nor is it intended to simulate extreme industrial conditions beyond those explicitly defined in the test procedure.
Technical Requirements and Test Procedure
Principle
A composite specimen (the textile under test plus a standard multifibre adjacent fabric) is immersed in a peroxide bleaching solution at defined concentration, pH, temperature, and duration. After rinsing and drying, the change in colour of the test specimen and the staining of the adjacent fabric are assessed using the standard grey scales.
Apparatus and Reagents
| Component | Requirement / Specification |
|---|---|
| Bleaching bath | Stainless steel or glass container with a thermostatic heating device (±1°C) |
| Peroxide solution | Hydrogen peroxide (30% w/w), stabilised; diluted to a 5 g/L active H₂O₂ concentration |
| pH control | Sodium hydroxide / sodium carbonate buffer to maintain pH 10.0 ± 0.2 |
| Stabiliser | Sodium silicate (optional, but recommended to control decomposition) |
| Adjacent fabric | Multifibre strip (e.g., DW or SDC type) conforming to ISO 105-F10 |
| Grey scales | Grey Scale for Colour Change (ISO 105-A02) and Grey Scale for Staining (ISO 105-A03) |
| Temperature controller | Accurate to ±1°C at the test temperature (typically 90°C or alternate temperature as specified) |
Procedure
- Prepare the composite specimen by sewing or stapling the textile sample (40 mm × 100 mm) to the multifibre strip.
- Pre-wet the composite in distilled water at room temperature for 10 minutes.
- Immerse the composite in the peroxide bath at a liquor ratio of 50:1 (bath volume to mass of specimen).
- Maintain the temperature at 90°C ± 1°C for 30 minutes (or an alternative cycle defined in the product specification).
- Remove the specimen and rinse thoroughly in running cold water, then air-dry at a temperature not exceeding 60°C.
- Condition the dried specimen in a standard atmosphere (21°C ± 1°C, 65% ± 2% RH) for at least 4 hours before rating.
Important: Peroxide solutions decompose rapidly at high temperature and alkaline pH. The bath must be freshly prepared and used within 15 minutes. Failure to control pH or temperature within tolerances will produce invalid results.
Assessment
Colour change of the test specimen is assessed by comparing it to the original, untested sample using the Grey Scale for Colour Change. The staining on each fibre type of the multifibre strip is assessed with the Grey Scale for Staining. Results are reported as a numerical grade from 1 (poor) to 5 (excellent).
Implementation Highlights
Laboratories implementing CAN CGSB 4.2 No. 55-M90 should ensure that technicians are trained to identify subtle colour differences. Standardisation of lighting (D65 illuminant, neutral grey surround) is critical for reproducible grading. The use of a spectrophotometric alternative, based on CIE Lab values, is permitted but must be validated against visual grey scale assessments.
Best Practice: Keep a set of reference grey scale tiles calibrated annually. Verify the performance of the peroxide test by running a known control fabric (e.g., a blue wool reference) in each batch.
When the product specification calls for testing at a different temperature (e.g., 60°C for delicate fabrics), the deviation must be noted in the report. The standard permits such modifications as long as the test conditions are fully documented.
Compliance and Quality Assurance
Compliance with CAN CGSB 4.2 No. 55-M90 is often a contractual requirement for textiles sold in Canada. A passing grade is typically Grade 4 or 5 for colour change and Grade 3–4 or higher for staining, although threshold levels depend on the end‑use application. For example, items intended for repeated bleach exposure (e.g., white shirts, uniform fabrics) may demand a higher resistance than decorative textiles that receive occasional bleach treatment.
Testing should be performed on production-identical samples, not on specially prepared “best case” specimens. Third-party certification bodies (e.g., accredited textile testing laboratories) are commonly used to verify compliance. The standard can be referenced in technical data sheets under the heading Colourfastness to Bleaching: Peroxide.
Non-compliance Risk: A product that fails this test may suffer unacceptable colour loss or staining during the first normal laundering if peroxide bleach is used. This can lead to customer returns, brand damage, and chargebacks. Always verify colourfastness to the washing conditions expected in the target market.
The standard does not include pass/fail criteria; it is purely a test method. Specifying the required grades and the frequency of testing (e.g., once per production batch) is the responsibility of the buyer or the quality assurance team.
Relation to International Standards
As noted, CAN CGSB 4.2 No. 55-M90 is technically identical to ISO 105-N01. However, the Canadian standard uses the CGSB 4.2 numbering system and includes some additional notes relevant to Canadian laboratory practice. For companies exporting from Canada, dual reporting (using both references) is accepted in most markets.
Frequently Asked Questions
Q: How does this method differ from chlorine bleach fastness tests?
A: CAN CGSB 4.2 No. 55-M90 uses an alkaline hydrogen peroxide solution (pH 10) at high temperature. Chlorine bleach tests (e.g., CGSB 4.2 No. 56 or ISO 105-N02) use an acidic sodium hypochlorite solution. The chemical reactions causing colour loss are different, and a product can perform well in one and poorly in the other. Both tests are required when bleach fastness is a general specification.
A: CAN CGSB 4.2 No. 55-M90 uses an alkaline hydrogen peroxide solution (pH 10) at high temperature. Chlorine bleach tests (e.g., CGSB 4.2 No. 56 or ISO 105-N02) use an acidic sodium hypochlorite solution. The chemical reactions causing colour loss are different, and a product can perform well in one and poorly in the other. Both tests are required when bleach fastness is a general specification.
Q: Can the test be performed with a single‑fibre adjacent fabric instead of multifibre?
A: The standard specifically requires a multifibre adjacent fabric to simultaneously assess staining on six common fibre types (wool, acrylic, polyester, nylon, cotton, and triacetate). If a single‑fibre fabric is used (e.g., only cotton), it must be stated in the report, but this deviates from the standard and may not be acceptable for certification purposes.
A: The standard specifically requires a multifibre adjacent fabric to simultaneously assess staining on six common fibre types (wool, acrylic, polyester, nylon, cotton, and triacetate). If a single‑fibre fabric is used (e.g., only cotton), it must be stated in the report, but this deviates from the standard and may not be acceptable for certification purposes.
Q: Is spectrophotometric assessment allowed?
A: Yes. CGSB 4.2 No. 55-M90 permits instrumental colour measurement as an alternative to visual grey scale rating, provided the instrument is calibrated and the chosen colour‑difference equation (e.g., CIE Lab ΔE*) correlates with the visual grade. The laboratory must have documented correlation data. However, for dispute resolution, visual assessment by trained operators with the standard grey scales is the referee method.
A: Yes. CGSB 4.2 No. 55-M90 permits instrumental colour measurement as an alternative to visual grey scale rating, provided the instrument is calibrated and the chosen colour‑difference equation (e.g., CIE Lab ΔE*) correlates with the visual grade. The laboratory must have documented correlation data. However, for dispute resolution, visual assessment by trained operators with the standard grey scales is the referee method.
Q: What are the required qualifications for technicians performing this test?
A: Technicians must have normal colour vision (verified by e.g., the Ishihara test) and be trained on the CGSB 4.2 series protocols. Annual proficiency testing with unknown samples is recommended to maintain internal competency. Accredited laboratories also undergo periodic audits covering this method.
A: Technicians must have normal colour vision (verified by e.g., the Ishihara test) and be trained on the CGSB 4.2 series protocols. Annual proficiency testing with unknown samples is recommended to maintain internal competency. Accredited laboratories also undergo periodic audits covering this method.
Last updated: 2026. This article is intended for informational purposes and does not replace the official standard. Always refer to the latest version of CAN CGSB 4.2 No. 55-M90 (2013) published by the Canadian General Standards Board.
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