Overview
ISO 7771:1985 specifies a laboratory method to determine dimensional changes of fabrics induced by cold-water immersion. It applies to fabrics that, in normal use, are exposed to cold water without agitation. The procedure measures fabric dimensions before and after a controlled soak-and-dry cycle and reports the percentage change in the lengthways and/or widthways directions.
Key topics and requirements
- Scope: Applicable to fabrics subjected to cold-water immersion without agitation.
- Conditioning: Specimens must be conditioned in the standard atmosphere for textiles according to ISO 139 prior to testing.
- Specimens:
- Wide fabrics: at least one specimen, cut at least 500 mm × 500 mm, edges parallel to length/width, avoid selvedges and within 1 m of ends.
- Narrow fabrics: at least three specimens, full width and at least 450 mm long; marking varies with fabric width (see ISO 7771 figures).
- Knitted fabrics: tested in double thickness with stable-thread seaming.
- Marking & measuring: Mark reference points per ISO 3759. For wide fabrics, three pairs of reference points in each direction with 350 mm between pair points; no point closer than 35 mm to edges. Narrow fabric points typically ~50 mm from ends.
- Apparatus & reagents:
- Watertight tray (~100 mm deep) large enough to lay specimen flat.
- Two plate-glass pieces (≈ 600 mm × 600 mm × 6 mm) for tension-free measurement.
- Steel rule graduated in millimetres.
- Wetting agent (0.5 g/L active matter), examples noted in the standard (e.g., alkyl sulphonates/soaps).
- Water temperature 15–20 °C; zero hardness preferred or adjusted with sodium hexametaphosphate/sodium triphosphate.
- Test procedure:
- Measure conditioned specimen, soak flat for 2 hours in water with wetting agent (depth ≥ 25 mm), remove without distortion, remove excess moisture, dry at 20 ± 5 °C, recondition and remeasure.
- Measurements taken between corresponding reference points; calculate percentage change for each dimension.
- Results & reporting: Record mean percentage dimensional change to the nearest 0.1%. Use positive sign for extension and negative for shrinkage. Test report must state compliance with ISO 7771 and any deviations.
Applications and users
ISO 7771 is used by:
- Textile testing laboratories for dimensional stability and shrinkage assessment
- Fabric manufacturers and mills for quality control and process validation
- Garment and home-textile producers to predict fabric performance after exposure to cold water
- R&D teams evaluating finishing processes, wetting agents or fiber blends
Practical benefits include objective comparison of fabrics, formulation of care instructions, and verification of supplier claims.
Related standards
- ISO 139 - Standard atmospheres for conditioning and testing textiles (conditioning requirements referenced)
- ISO 3759 - Preparation, marking and measuring of fabric specimens and garments in tests for dimensional change
Keywords: ISO 7771, textiles testing, dimensional changes, cold-water immersion, fabric shrinkage, dimensional stability, specimen conditioning.
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