Water Repellency Test of Fabric by Spray Rating Tester

Water repellency is a fabric property that measures a material’s resistance to surface wetting and water penetration. Unlike waterproof fabrics — which must withstand a hydrostatic water column of at least 1 meter before penetration — water-repellent fabrics resist wetting but will eventually allow water through under sufficient pressure or prolonged exposure. The primary goal of water-repellent finishes is to protect textile materials from surface saturation during light rain or accidental water contact.

Water repellency is achieved by treating fabric with paraffin waxes, silicones, acid-based melamine resins, or fluorocarbon polymers. These treatments reduce the free surface energy of fibers below water’s surface tension of approximately 72 mN/m at 20°C, causing water droplets to bead and roll off rather than spreading across the fabric surface. Application methods include film coating, lamination, padding, or spray application.

AATCC Water Repellency Test of Fabric by Spray Rating Tester

The American Association of Textile Chemists and Colorists (AATCC) defines water repellency as the resistance of a fabric to surface wetting by water. The AATCC Test Method 22 — Water Repellency: Spray Test quantifies this property using a visual rating scale. The tested material’s result is determined by comparing the fabric’s appearance against the standardized AATCC photographic reference chart after exposure to a controlled water spray. This method is technically equivalent to ISO 4920 and BS EN 24920.

Apparatus

• Spray Tester (conforming to AATCC 22 specifications, with a 150 mm spray head distance)
• Scissors
• Fabric specimen (minimum 6 in × 6 in / 152 mm × 152 mm per test)
• Measuring cylinder (250 ml capacity, Class A tolerance)
• Thermometer (0–50°C range, ±1°C accuracy)
• Conditioned water (250 ml per test at 27°C ± 1°C)
• Specimen hooping frame (6-inch / 152 mm diameter embroidery hoop)
• AATCC 22 photographic rating scale chart
• Collection basin (positioned under the specimen area)

Precautions

Water temperature must be maintained at 27°C ± 1°C (80°F ± 2°F) throughout the test. The water shall be poured steadily at a uniform flow rate over 25–30 seconds. A collection basin must be positioned under the specimen area to capture run-off water. Testing must be conducted in a draft-free environment to ensure consistent spray distribution.

Sample Preparation

Condition the fabric specimens for a minimum of 4 hours in the standard testing atmosphere before testing. Cut each specimen to fit the 6-inch (152 mm) diameter specimen hoop with sufficient tension to prevent folding or creasing. Prepare a minimum of 5 specimens per sample to obtain a reliable average rating.

Standard Testing Atmosphere

The standard atmosphere for textile testing must be maintained at 20°C ± 2°C (68°F ± 3.6°F) and 65% ± 2% relative humidity. Moisture content in the fabric directly affects test results — changes in fabric weight from atmospheric moisture can compromise the accuracy of the spray rating. The specimens must reach moisture equilibrium in this environment before testing begins.

Working Procedure

1. Secure the conditioned fabric specimen flat in the specimen hoop, ensuring the fabric surface is free of folds, creases, or tension marks.
2. Place the specimen hoop into the spray tester specimen area, oriented so the fabric is inclined at a 45° angle to the horizontal.
3. Measure exactly 250 ml of distilled or deionized water and verify the temperature is 27°C ± 1°C using the calibrated thermometer.
4. Position the water reservoir funnel at the top of the instrument and pour the 250 ml of water at 27°C steadily over 25–30 seconds, maintaining uniform distribution across the spray head.
5. After all water has been sprayed, immediately remove the specimen hoop and compare the wetting pattern on the fabric against the AATCC 22 photographic rating scale.
6. Record the rating to the nearest whole number. Interpolation between ratings is not permitted.
7. Repeat steps 1–6 for all 5 specimens. Record individual ratings in a data log.
8. Calculate the arithmetic mean of all 5 individual ratings. Round the final result to the nearest whole number — this is the reported spray rating for the sample.

AATCC 22 Spray Test Rating Scale

The AATCC 22 spray rating scale ranges from 0 to 100, with higher values indicating greater water repellency. The rating is determined by visual comparison against the standardized AATCC photographic chart.

Key Parameters at a Glance

Water Repellent Treatment Chemistry

Modern water-repellent treatments fall into four main chemical categories, each with distinct performance characteristics:

The surface tension of water at 20°C is approximately 72 mN/m — one of the highest among common liquids. Effective water-repellent finishes must reduce fiber surface energy below this threshold. Fluorocarbons achieve the lowest surface energy of all treatment types, which is why they are specified for high-performance outerwear and technical textiles. Silicone-based treatments are widely used in mid-tier applications where cost-effectiveness and environmental compliance are priorities.

Industry Applications and Requirements

Water-repellent fabrics serve diverse market segments with specific performance thresholds:

1. Sportswear and activewear: Spray rating 70–90 required; durability through 20–30 wash cycles; must maintain breathability
2. Military and tactical apparel: Spray rating 80–100; must withstand 50+ wash cycles; often combined with flame-retardant finishes
3. Home textiles (upholstery, awnings): Spray rating 70–80; high UV and mildew resistance required; 3–5 year outdoor durability
4. Medical bandages: Must prevent both water ingress and biological fluid wicking; cytotoxicity testing mandatory
5. Automotive interiors: Spray rating 70+; resistance to skin oils, sun lotions, and food stains; colorfastness required

Remarks

The AATCC Test Method 22 — Water Repellency: Spray Test is one of the most widely adopted quality control procedures in the textile industry. Laboratories, manufacturers, and brand quality assurance teams use it to verify that water-repellent treatments meet specified performance thresholds. The spray test is particularly valued for its speed, reproducibility, and low equipment cost.

Equivalent standards include ISO 4920:1981 (confirmed current in 2026) and BS EN 24920, both of which use the same spray principle and rating methodology. When a fabric specification calls for “spray rating of 70” or higher, any of these three standards may be used for compliance testing.

References

• American Association of Textile Chemists and Colorists. (AATCC). AATCC Test Method 22 — Water Repellency: Spray Test. AATCC Technical Manual, current edition. https://www.aatcc.org/
• International Organization for Standardization. (1981). ISO 4920: Textile fabrics — Determination of resistance to surface wetting (spray test). ISO. https://www.iso.org/
• British Standards Institution. BS EN 24920 — Textile fabrics: Determination of resistance to surface wetting (spray test). BSI. https://www.bsi.org.uk/
• Schindler, W. D., & Hauser, P. J. (2004). Chemical Finishing of Textiles. Woodhead Publishing. In: ScienceDirect Topics — Repellency. https://www.sciencedirect.com/topics/engineering/repellency
• Hill, P. J., Taylor, M., Goswami, P., & Blackburn, R. S. (2017). Substitution of PFAS chemistry in outdoor apparel and the impact on repellency performance. Chemosphere, 181, 500–507. https://doi.org/10.1016/j.chemosphere.2017.04.122
• Schellenberger, S., Hill, P. J., Levenstam, O., Gillgard, P., Cousins, I. T., Taylor, M., & Blackburn, R. S. (2019). Highly fluorinated chemicals in functional textiles can be replaced by re-evaluating liquid repellency and end-user requirements. Journal of Cleaner Production, 217, 134–143. https://doi.org/10.1016/j.jclepro.2019.01.160