Overview
ISO 4920:2012 - Textile fabrics - Determination of resistance to surface wetting (spray test) - specifies a standardized spray test to assess a fabric’s resistance to surface wetting by water. The method measures how well the face of a fabric resists wetting (spray rating) and is widely used to evaluate water‑resistant or water‑repellent finishes. It is explicitly not intended to predict rain‑penetration resistance because it does not measure water penetration through the fabric.
Key topics and technical requirements
- Test principle: A defined volume of distilled or de‑ionized water is sprayed onto a fabric specimen mounted on a ring inclined at 45°, and the resulting wetting of the fabric face is visually rated.
- Specimens: At least three specimens, each ≥ 180 mm square, taken from different areas of the fabric to represent the material.
- Apparatus: Spray device with funnel and metal nozzle, specimen holder (ring/hoop), and support arranged so the specimen center is at the specified distance below the nozzle.
- Water and volumes: (250 ± 2) ml of distilled or fully de‑ionized water, poured so flow duration is between 25 s and 30 s; water temperature recorded (common options: 20 ± 2 °C or 27 ± 2 °C).
- Orientation and procedure: Fabric face uppermost; warp/length aligned parallel to water flow unless otherwise specified; immediate tapping and visual assessment after spray.
- Evaluation: Spray rating scale 0–5 (0 = complete wetting; 5 = no sticking or wetting). Photographic rating standards (AATCC photographic scale equivalence) may be used; intermediate ratings of 0.5 permitted.
- Conditioning and atmosphere: Conditioning/testing per ISO 139 (standard atmospheres) unless otherwise agreed.
- Test report requirements: Reference to ISO 4920, atmosphere, water temperature, spray rating per specimen, sample identification, and any procedural deviations.
Applications and users
- Quality control and production acceptance for textile mills and finishers assessing water repellency or surface treatments.
- R&D and product development teams evaluating finishes, coatings, or treatments for apparel, outdoor gear, upholstery, and industrial textiles.
- Independent testing laboratories issuing compliance and performance reports for clients and brands.
- Procurement and specification writers using standardized spray ratings to compare materials.
- Note: Use ISO 4920 for surface wetting performance; use separate tests when water penetration or hydrostatic resistance must be measured.
Related standards
- ISO 139 - Textiles - Standard atmospheres for conditioning and testing
- ISO 3696 - Water for analytical laboratory use (referenced for water quality)
- AATCC Test Method 22 - Water Repellency: Spray Test (photographic scale equivalence)
Keywords: ISO 4920:2012, spray test, textile fabrics, water repellency, surface wetting, spray rating, textile testing standards, AATCC 22.
