Overview
EN ISO 105-X08:1997 (ISO 105-X08:1994) specifies a laboratory method to determine the resistance of textile colour to the action of soap solutions used in degumming raw silk. The method applies to textiles of all kinds except loose fibre. A composite specimen is prepared with the test sample held between two adjacent fabrics, treated with a defined soap solution under reflux, then rinsed, dried and evaluated. Colour change of the specimen and staining of adjacent fabrics are assessed using the ISO grey scales.
Practical value: this standard supports quality control, dye selection and process validation where exposure to soap/degumming treatments is expected (for example in silk finishing and testing dyed goods).
Key Topics
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Scope and purpose
- Tests colour fastness to soap solutions such as those used for degumming raw silk.
- Excludes testing of loose fibre.
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Test principle
- A specimen (fabric or yarn formed into a layer) is sandwiched between two single-fibre adjacent fabrics and sewn to form a composite specimen.
- The composite is refluxed in a lightly boiling soap solution, rinsed, dried and assessed.
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Apparatus and reagents
- Vessel with reflux condenser (capacity ~500 ml).
- Soap complying with specified limits (low free alkali, minimum fatty matter, free from optical brighteners).
- Soap solution prepared at 7 g soap per litre of grade 3 water.
- Anhydrous sodium carbonate (Na2CO3) and grade 3 water.
- Two single-fibre adjacent fabrics: one made of raw silk (section F06 of ISO 105-F:1985) and one made of the same or predominant fabric as the specimen.
- Grey scales for assessment (ISO 105-A02 and ISO 105-A03).
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Procedure highlights
- Composite specimen size typically 40 mm x 100 mm for fabric samples; yarns are formed into a layer and secured.
- Liquor ratio 100:1; treat under reflux for 10 minutes, then add 0.5 g Na2CO3 per litre and continue boiling lightly for a further 110 minutes (2 hours total).
- Rinse in grade 3 water, then in cold running tap water, squeeze and dry in air at temperatures not exceeding 60 °C.
- Assess colour change and staining against the grey scales and record numerical ratings.
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Reporting
- Include the ISO reference (ISO 105-X08:1994), sample identification, and numerical grey scale ratings for both colour change and staining.
Applications
- Quality control in textile mills and dye houses exposed to degumming or soap treatments.
- Validating dye selection and finishing processes for silk and blended fabrics.
- Laboratory compliance testing and product specification verification.
- Research and development of detergents, dyes and finishing processes related to degumming.
Related Standards
- ISO 105-A01:1994 - General principles of testing
- ISO 105-A02:1993 - Grey scale for assessing change in colour
- ISO 105-A03:1993 - Grey scale for assessing staining
- ISO 105-F:1985 - Standard adjacent fabrics (sections F06–F08 referenced for raw silk and other adjacent fabrics)
For laboratories and product teams, EN ISO 105-X08:1997 provides a repeatable, standardized method to evaluate how dyeing performs when textiles undergo soap/degumming exposures, enabling consistent quality decisions and compliance reporting.