By Ella Brown
Reading time: 5 minutes
What is waterproof?
When a garment is waterproof, it means water cannot penetrate through the fabric. Waterproof garments have impermeable and breathable qualities obtained by integrating a 2-3 layer "sandwich" of fabric: a DWR treated outer layer, a breathable waterproof membrane, and sometimes, a fabric backer.
The waterproofness of a textile depends on:
- The water-repellent and impermeability of its textile;
- The breathability of the textile;
- The waterproofness of its seams.
Water repellency and waterproofness work together but are not the same. Learn more about water repellency here and breathability here.
Textile and Design
Waterproofness doesn't depend on the fabric alone, it also depends hevily on the desidn and conceptualization of the garmet in question. For example, the waterproofness of a rain jacket would deoend on the impermeability and breathability of the fabric, the junctions, and the design of the jacket:
- Is the fabric waterproof? Does it have a DWR treated outer layer and a waterproof membrane? How heavy is it?
- Are the seams thermo-welded or thermo-glued with sealing strips?
- Are the zippers waterproof? If not, is there a piping beneath the zipper? (A piping is an extra inch or so of fabric that is sewn under the zipper with a little fold to prevent water from actually entering your coat through the zipper)
- How is the overall desgin of the coat? Is the coat fitted in a way where water rolls down and off the jacket instead of pooling near the collar or near the seams?
- How are the pockets designed? Do they have waterproof zippers? Do they have a flap covering them to prevent water from entering?
If you said no to any of these questions, your jacket isn't completely waterproof.
What is the composition of a waterproof textile?
The outermost layer (the colorful one that you see) is called the face layer. The face layer – usually nylon or plyester – is treated with a thin layer of DWR (Durable Water Treatment) which reduces the surface tension of the fabric, forcing the water droplets to bead and roll off instead of seeping into the fabric. DWR treatments are made of a chemical called Polytetrafluoroethylene (PTFE ) that is rubbed into the fabric to ensure that all the fibers are coated.
The DWR treated face layer also ensures breathability because it still allows for the tiny water vapor particles to escape from the inside, leaving the bigger water dropples on the outside. The pores on the outer layer of the fabric are 0.0002-0.0003mm big, while the pores on the membrane are even smaller at 0.0002-0.0003mm big. The average size of a water droplet ranges between 0.02-0.30mm in diameter, making it impossible for the water droplet to fit through the tiny pores in the fabric. On the other hand, the tiny particles of perspiration are small enough to fit through the pores, therefore letting the water vapor on the inside of your coat dissipate.
The second – or middle layer – is a tightly woven waterproof membrane with billions of tiny pores that acts as an impermeable layer while simultaneuously allowing the ventilation of bodily water vapors and perspiration.
The third layer is an optional layer called a backer fabric. The addition of a backer fabric is usually made of gives the waterproof material a more comfortable skin-to-skin feel and also protects the membrane from body oils and perspiration. However, the addition of a backer fabric does make the waterproof material have a slightly heavier feel. Waterproof garmets that have the addition of a third layer are especially good for cooler climates as it also gives an extra layer of breatheable insulation.
A textile can thus be, for example:
- Water-repellent but not waterproof (as are often softshells), in which case water glides on the garment in fine and / or short rain, but enters the garment in intense and / or long rain;
- Non-water-repellent but waterproof (membrane), in which case the outer layer of the textile gorges with water regardless of the intensity and duration of the rain (which can cause a feeling of freshness if the waterproof membrane is in contact with the skin), but does not penetrate the raincoat;
- Water-repellent and waterproof (membrane), in which case the outer layer of the textile is gorged with water only in intense and / or long rain, and does not penetrate the rain poncho under any circumstances.
How do you measure waterproofness?
The Schmerber Test measures the impermeability of fabric on a scale of EN ISO 811. EN ISO 811 is a hydrostatic pressure test that determined the level of resistance a product has against water penetration.
*EN ISO 811 GRAPH / VISUAL*
A textile alone cannot be completely impermeable without waterproof seams because the water will leak through the holes drilled in the textile during manufacturing. We, therefore, advise you to choose a garment whose seams exposed to rain are thermo-welded or thermo-glued with sealing strips.
Like all products, the waterproofness of a material fades with the duration the textile is exposed to rain and its intensity, but also with the wear and washing of rain equipment.
What is the link between waterproofness and breathability?
The breathability of a waterproof material is extrememly important to the overall comfort and function of the garmet.
Say you have a rubber raincoat that is 100% waterproof. If you are standing still outside in a rainstorm, the rubber raincoat will do its job and keep the water from seeping from the outside to the inside of the coat. However, the second you start to sweat, the raincoat will no longer be doing its job if there isn't a way for the water on the inside of the coat escape. Without breathability, you will be wet on the inside of your coat, which is never fun.
If you have a waterproof raincoat made out of breathable material such as GORE-TEX, Dermizax, Polartec Neo Shell, or Sympatx, you could exert energy in the rain or snow and stay dry at the same time. GORE-TEX is considered to be the best waterproof material on the market currently becaise of how breathable and impermeable it is.
If you are one that tends to bike or walk in the rain while wearing a backpack, it's important to wear a higher-quality waterproof jacket if you intend to stay dry for longer periods of time. If you wear a backpack over your rain jacket, the pressure from the backpack will eventually force the material to leak over time. Higher-quality materials will be more durable against pressure and degradation.
What is the difference between waterproofness and water repellency?
The difference between waterproofness and water repellency