The testing methon of Spray Rating Tester

Textile water resistance property test is a wide concept which is involved with 3 types of different testing methods: Surface water-repellent test (spray test method), Water permeability resistance test method (hydrostatic pressure), Simulate the rain test (horizontal injection method). Also it requires different manufacturing craft and requirements accordingly.  
This article will introduce first test method: Surface water-repellent test (spray test method) 
Surface wetting resistance(spray rating) of fabrics, is to spray on fabrics’ surface by a certain amount of water ( usually 250ml) through standard spray nozzle (with 19 holes with bore diameter in about 0.86 ), and within predetermined time 25-30 seconds, so as to observe the spray rating. This method only assess the surface spray rate, not including fabric contrary water penetration state, also not available for checking fabric rain - proof permeability. 
The common test standards include AATCC 22, ISO 4920, GB/T 4745, JIS L1092, etc. 
Standard spray rating as follows(The bigger number is, the better spray resistance effect is). 
AATCC 100 (ISO 5 Grade): Sample surface without drop of water or wet situation 
AATCC 90 (ISO 4 Grade): A little wet at the spray point on surface of sample 
AATCC 80 (ISO 3 Grade): Wetting of sample surface at spray point 
AATCC 70 (ISO 2 Grade): Partial wetting of sample face beyond the spray points 
AATCC 50 (ISO 1 Grade): Complete wetting of entire sample face beyond the spray points 
AATCC 0 (ISO 0 Grade): Complete wetting of the entire face of the sample. 
In the process of rating, the sample is rated 0.5; This is clearly defined and rated in GB/T 4745. 
The surface of the fabric repellent effect is mainly from the surface tension of the fabric, when the fabric surface tension is less than the surface tension of the water, the water will not be absorbed by the fabric, and on the surface of the fabric to form granular water droplets or slip out of the fabric surface directly, and not wet fabric.