Waterproofing is simple: if water on the outside of the garment/shoes/tent doesn't get inside, the thing is waterproof, right? Well, yes and no. There are degrees of waterproofness in outdoor clothing, and here's why.
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We all know that waterproof garments are nothing without their breathability. After all, a black bin bag is waterproof but you wouldn't wear one hiking as you'd sweat like a sumo wrestler taking a spinning class in the jungles of Borneo. So what is this mystical breathability and from whence does it come?
Simply put, a waterproof/breathable membrane is a very thin layer of expanded polytetrafluoroethylene (PTFE), a synthetic polymer (i.e. a plastic sheet) containing holes that are too small for water molecules to pass through yet large enough to allow water vapour to pass through. So, the raindrops can't get in but the evaporated sweat coming off your hard-working body can get out. Getting the size of the holes perfect to maximise both operations is tricky, plus expensive. Generally, the more breathable a fully waterproof membrane is, the more expensive it will be to produce.
Measuring Waterproofness.
Hydrostatic head, measured in millimeters (mm), is a measure of how waterproof a fabric is. In the case of a 10k or 10,000 mm fabric, if you put a cylinder with inner dimensions of 1” x 1” over a piece of said fabric, you could fill it with water to a height of 10,000 mm (10m) before water would begin to leak through. The higher the number, or 'water column', the more waterproof the fabric.
Measuring Breathability
Breathability is normally expressed in terms of how many grams (g) of water vapor can pass through a square meter (m2) of the fabric from the inside to the outside in a 24 hour period. In the case of a 20k (20,000 g/m2) fabric, this would be 20,000 grams of moisture transfer. The larger the number, the more breathable the fabric. Simple.
Except that this figure is only for the membrane, not the finished article. The construction of the jacket will also have an effect. In a three layer jacket (3L), the membrane (the middle layer) is bonded to the outer face fabric and a protective internal woven layer. In a 2.5 layer jacket the woven layer is replaced by a screen printed 'half' layer to protect the membrane. This is a lighter solution but doesn't protect the membrane as well and also doesn't have such a nice feeling against the skin, often being described as 'clammy'. Generally three layer garments are more breathable.
The last thing to consider is DWR, or Durable Water Repellency, the chemical treatment that is applied to the outside of waterproof garments to make water bead up and roll off. This treatment wears off over time and although its disappearance in no way affects the performance of the membrane, without it rain will sink into the face fabric and significantly impair the breathability of the garment. Therefore in order to maximise the breathability of your jacket you should wash it in special soft detergent to maintain the DWR and reproof it regularly.
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Now that you know what's going on, the following table lists some common membrane brands that you may come across in Australia, along with their waterproof and breathability ratings. Hopefully this will give you an idea of what to look for next time you are replacing a jacket, pants or boots.
Whether you are hiking through a torrential downpour, skiing in the mountains, or navigating a rainy urban commute, having the right outerwear can make all the difference. Waterproof breathable fabric is the unsung hero in outerwear, offering protection from the elements while keeping you comfortable. In this comprehensive guide, we will delve into everything you need to know about waterproof breathable fabric, from its construction to care.
Waterproof breathable fabric is a specially engineerted textile designed to repel water while allowign moisture vapor (like sweat) to escape from inside, keeping you dry and comfortable in various weather conditions. This type of fabric is commonly used in outdoor clothing, including rain jackets, ski pants, hiking gear, and in various industrial and military applications.
Contact us to discuss your requirements of Waterproof Breathable Membrane. Our experienced sales team can help you identify the options that best suit your needs.
A fabric’s waterproof rating is determind by its ability to resist the penetration of water. This resistance is achieved through the combination of the outer shell material, DWR finish, and waterproof membrane. The key factor that make fabric waterproof include:
A durable water repellent (DWR) coating is a treatment applied to the outer shell of waterproof fabric. It works by reducing the surface tension of water droplets, causing them to bead up and roll off the fabric rather than being absorbed like when raindrops hit the finish on a car or a plant leaf. Over time, DWR treatments can wear off dur to regular wear, exposure to dirt and oils, and repeated washing. To maintain optimal performance, it is essential to regularly wash your outerwear and periodically reapply DWR using products specfically designed for this purpose.
Hydrophobic membranes play a crucial role in the functionality of outerwear by providing waterproof and breathable properties. These membranes are typically made of polymers or synthetic materials with hydrophobic characteristics, meaning they repel water. When integrated into outerwear, these membranes function as a barrier that prevents external moisture, like rain or snow, from penetrating while allowing internal moisture, such as sweat vapor, to escape. The hydrophobic nature of these membranes ensures that water droplets bead up on the fabric’s surface and slide off, rather than being absorbed. This dual-action mechanism maintains the wearer’s comfort by keeping them dry from external elements and allowing their body heat and moisture to dissipate, resulting in a more breathable and comfortable outdoor experience. Additionally, advanced hydrophobic membranes often include microscopic pores that facilitate water vapor molecules’ movement while blocking larger liquid water molecules, further enhancing the breathability and waterproofing of the outerwear.
Hydrophilic membranes in outerwear function by utilizing a specialized material that exhibits inherently affinity for water. These membranes are typically integrated into the fabric layers of outdoor garments to provide waterproof and breathable properties. The hydrophilic membrane is engineered to have microscopic pores that are smaller than a water droplet but larger than water vapor molecules. When snow, rain, water, or any liquid contacts the outer surface of the garment, the hydrophilic membrane actively attracts and absorbs the water, preventing it from penetrating the inner layers.
Simultaneously, the moisture vapor produced by the body’s perspiration is allowed to escape through these pores due to the difference in pressure and the membrane’s hydrophilic nature, ensuring breathability. This combination of repelling external moisture while permitting internal moisture transfer helps keep the wearer dry and comfortable, making hydrophilic membranes a fundamental technology in waterproof and breathable outdoor apparel.
Waterproof breathable fabrics are produced with the construction of layers of fabric and membrane, fused together with heat and glue, creating a fabric laminate. The most common fabric laminates consist of the top fabric (the outer shell fabric), or face fabric, a membrane layer, and a backer (or liner) fabric. The number of layers in a fabric laminate creates the expectation for durability, breathability, and overall function of the laminate. The most common laminate types are:
When waterproof fabric laminates are constructed into garments, footwear, and accessories, different components are used to lock out moisture and help increase breathability. These components help reinforce any potential weak points, while still maintaining the intended structure and design:
Even if a garment is constructed using a waterproof membrane with a DWR-treated face fabric, the waterproof and breathability ratings can vary depending on the materials used and how the garment is constructed. By reviewing the waterproof and breathability ratings in waterproof outerwear and footwear, you can find the right piece for your favority activity, lifestyle, or region.
Waterproofness (or in industry terms water column) measures the level of water pressure that a fabric can withstand before water penetrates it. Waterproofness is measured in millimeters and is tested by putting a 1”x1” cylinder over a piece of fabric and filling it with water until the water leaks through. As the material withstands a greater amount of water presure, illustrating a greater water pressure, the measured water column increases.
Water column ratings give you a roadmap as to what garment works best in the conditions you face. If you need a waterproof jacket for protection as you go for a run outdoors, you don’t need as high of a waterproof rating as someone in more rainy conditions carrying a heavy backpack. The below chart can help you determine what level of waterproofness is the best match for your activities:
Much like how waterproofness keeps you comfortable and dry on the outside, breathability keeps you comfortable and dry on the inside of your garment. By selecting the appropriate level of breathability in your garment, you can help regulate your body’s temperature and help prevent overheating. Breathability is measured by the moisture vapor transfer rate, or MVTR. MVTR measures the rate in which moisture permeates through a fabric in grams/meter2 in a 24-hour period. The higher the MVTR is in a fabric, the more breathable the fabric is, helping you stay dry and comfortable.
Technical outerwear benefits from regular washing to keep it performing at its best. Before washing, carefully review and follow the manufacturer’s care instructions. Most waterproof garments can be cleaned with the following instructions:
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