Understand the difference between Water repellency/Water resistance/Water penetration/Waterproofness

When it comes to water-related performance testing of footwear and apparel products, it is inevitable to be inundated by “water repellence”, “water penetration”, “water resistance”, and “waterproofness”. What do they mean, and what is the difference? Let’s dive in.

Definition by standards
  1. Definitions by national and international standards:
● Water repellency: the characteristic of fiber, yarn, or fabric to resist wetting
  • ASTM D1566-15
  • AATCC manual
  • ISO 18696:2006 3.2
● Water penetration: the passage of water from one surface to the other surface
  • ISO 5633:1983 4
● Water resistance: the characteristic to resist wetting and penetration by water
  • ASTM D1566
  • AATCC manual
  • ISO 22958:2021 3.1
● Waterproofness: property of impenetrability by liquid water
  • ASTM D1566
  1. Definitions by test standard methods for footwear and apparel testing
● Water repellency:
  • AATCC 22-2014 Water Repellency: Spray Test
  • AATCC 70-2014 Water Repellency: Tumble Jar Dynamic Absorption Test
  • ISO 17231-2017 Leather – Physical and mechanical tests – Determination of water repellency of garment leather
● Water penetration:
  • ISO 811-2018 Textiles — Determination of resistance to water penetration — Hydrostatic pressure test
  • ISO 17230-2006 Leather – Physical and mechanical tests – Determination of water penetration pressure
● Water resistance:
  • AATCC 35-2013 Water Resistance: Rain Test
  • AATCC 127-2014 Water Resistance: Hydrostatic Pressure Test
  • ISO 17702:2003 Footwear – Test methods for uppers – Water resistance
  • ISO 5403-1/2:2011 Leather – Determination of water resistance of flexible leather
● Waterproofness
  • ASTM D3393-1991(2022) Standard Specification for Coated Fabrics — Waterproofness
  • GB/T 16641-2019 Footwear – Test methods for whole shoe – Dynamic waterproofness)
  • DIN SPEC 53264-2017 Footwear – Test methods – Determination of water passage(waterproofness)
  • ISO 20344:2021 5.7 Personal protective equipment – Test methods for footwear – Leak proofness

Water repellence refers to the degree to which the material is resistant to wetting by water. The emphasis is on the effect of water on the material itself, rather than its ability to resist water penetration.

Resistance to wetting and resistance to water penetration have different meanings. Strong resistance to wetting does not mean that the material is impervious to water. However, in the case that the water droplets cannot moisten at all (such as the lotus leaf effect), it also literally has certain waterproofness.

There are more than one test methods and evaluation methods for the wettability of materials, mainly as follows:

Test method:

  • Spray test: AATCC 22, ISO 17231
  • Absorption test: AATCC 70

Evaluation method:

  • The water level of the material surface (appearance change) : such as AATCC22 (Including ISO 4920, GB/T 4745),ISO 17231 section 7.4
  • Calculate the water absorption of the sample: AATCC70, ISO 17231 section 8

Water penetration refers to the ability of water to penetrate a material or finished product.

Through the amount of water permeating through the material (quantity, quality, area, etc.) , it evaluates the strength of the material’s waterproofness. It is to clearly assess the waterproofness of a single material. It is also quite different from resistance to wetting. Strong permeability resistance does not mean that it also has the ability to resist wetting.

Water resistance refers to the material’s ability to resist wetting and penetration by water.

In standards such as ISO, ASTM, AATCC, GB, there are basically two parts: anti-wetting and penetration. That means examining both water repellency and water penetration. However, wetting is usually measured by the amount of water absorbed rather than the level of wetting. For example, the indicators of ISO 17702:2003 assessment are water absorption (wetting) and water transmission (penetration).

But in some cases, water resistance means penetration. In the AATCC standard system, the definition of water resistance also includes two parts: wetting and penetration. In fact, the water resistance parameter in the AATCC standard only evaluates water penetration (standards include AATCC TM35, AATCC TM42, AATCC TM127).

Waterproofness refers to the ability of a material or finished product to prevent water penetration.

It is generally measured by whether water is not allowed to penetrate at all. Its role, and that of water penetration, is to examine whether the material or finished product is waterproof. The most striking difference is that assessing water penetration is by the amount of water, while waterproofness is by whether it is permeable.

Note: The above analysis is only based on ISO, ASTM, AATCC, GB standards, though buyer standards are generally consistent with the above rules.

Practical application

While there are different meanings with these terms, the use of these terms in the market may be muddled and arbitrary.

Take water repellency as an example. Although repellency is defined in the standard to evaluate the resistance to wetting of materials, in shoe material testing, two different testing requirements exist, namely, resistance to wetting and penetration. Such significance varies from different materials, processes and post-treatment methods on shoe materials.

Therefore, when your products are required to meet the water repellency requirement, you should first understand their underlying purpose to match quality needs.  Conversely, water resistance is the way to go when assessing the penetration of finished products.

The safest bet is to consider both the requirements and test standards, especially when the product market is so awash with the claims of water repellency, water penetration, water resistance and Waterproofness.

Share this article

Other Articles