In this blog post, we’ll explore the principles, structure, pros, and cons of Gore-Tex—which blocks rain while allowing sweat and water vapor generated by the body to escape—as well as recent technological advancements.
Have you ever gotten soaked in sweat while trying to stay dry in the rain? Imagine walking in a raincoat on a rainy day. It’s raining, but it’s hot, so you start to sweat. You put on the raincoat to stay dry, but the sweat ends up soaking your clothes anyway. Haven’t you experienced this ironic situation before? But now, you don’t have to deal with it anymore—thanks to Gore-Tex. Gore-Tex, commonly found not only in specialty hiking stores but also in a wide variety of outdoor products, how does it solve this problem?
First, let’s take a look at what Gore-Tex actually is. Gore-Tex is a high-performance material—both the name of the material developed by Dr. Gore and the brand name itself. To be precise, the core technology behind Gore-Tex was born in 1969 when Bob Gore discovered expanded polytetrafluoroethylene (ePTFE)—a material with microscopic pores—while rapidly stretching polytetrafluoroethylene (PTFE). Since then, Gore-Tex has evolved into a leading functional material that combines the distinct properties of waterproofing, windproofing, and breathability within a single product. Recently, new Gore-Tex membranes using not only ePTFE but also expanded polyethylene (ePE) have emerged, and products featuring ePE membranes began hitting the market starting with the Fall/Winter 2022 season.
To understand the characteristics of Gore-Tex, it is necessary to examine the structure of its core component: the membrane. Traditional Gore-Tex membranes consist of an extremely thin and fine porous structure, reportedly containing approximately 9 billion pores per square inch. These pores are too small for water droplets to pass through but large enough for water vapor to escape. Generally, Gore-Tex describes the pore size as approximately 0.2 micrometers—much smaller than a water droplet but much larger than a water vapor molecule. Therefore, liquid water from the outside cannot easily pass through, but water vapor generated by the body can pass through the membrane. However, it would not be accurate to simply explain this as “it’s the same water, just in different sizes.” Raindrops consist of countless water molecules aggregated into a liquid state and, due to factors such as surface tension, cannot easily pass through the pores; in contrast, when sweat evaporates, it moves in the form of individual water vapor molecules, allowing it to pass through the membrane’s microscopic pores. This principle is similar to how, when a fisherman hauls in a net, the seawater drains out but the fish remain trapped inside.
However, the fine porous structure of the Gore-Tex membrane alone is not sufficient to fully deliver both waterproofing and breathability. In fact, Gore-Tex garments are constructed using a laminate structure that bonds the membrane to multiple layers of fabric, and various elements work together—such as the use of seam-sealing tape to prevent water from penetrating through the seams. In particular, the outer fabric is often treated with DWR (Durable Water Repellent), a durable water-repellent finish. DWR utilizes the fabric’s hydrophobic properties to help raindrops form beads that roll off rather than soaking into the fabric. Since the garment can feel cold and damp if the outer fabric becomes thoroughly saturated—even if the membrane maintains its waterproof function—DWR plays a crucial role in maintaining comfort. On the other hand, the Gore-Tex membrane itself acts as the core layer responsible for waterproofing and breathability. Therefore, rather than simply explaining—as was done in the past—that Gore-Tex’s functionality is achieved only by applying Teflon to the outer shell and using a hydrophilic material for the inner lining, it is more accurate to understand that waterproofing and breathability are achieved through the combined action of the membrane, the outer fabric, the lining, and the water-repellent treatment.
As such, Gore-Tex offers numerous advantages befitting a high-performance fabric. It is not only waterproof and windproof but also features breathability that allows moisture generated by the body to escape. However, Gore-Tex is not without its drawbacks. Gore-Tex products are often more expensive than standard functional clothing, which can be a burden for consumers. Furthermore, the performance of Gore-Tex products is not permanently maintained in all situations. In particular, the DWR applied to the outer fabric is not a permanent treatment, so its water-repellent properties can gradually weaken due to wear, friction, dirt, and detergents. However, this should not be equated with the loss of the Gore-Tex membrane’s inherent waterproofing capability. Even if the DWR weakens, the membrane can still maintain its waterproofing capability; however, if the outer fabric absorbs water, the garment may feel heavy and cold, or it may seem as though its breathability has decreased. Therefore, it is important not to avoid washing Gore-Tex products, but rather to wash and dry them properly according to the manufacturer’s care instructions. Currently, Gore-Tex recommends washing standard outerwear in water around 40°C and, after drying, reactivating the DWR by using a dryer on a low heat setting for about 20 minutes if necessary. If the water-repellent properties are not restored through washing and drying alone, the garment can be retreated using a separate DWR product.
As alternatives to expensive Gore-Tex, various companies have developed a range of materials that offer breathability and waterproofing similar to Gore-Tex. Notable examples include functional materials such as Sympatex and Hipora. These materials achieve waterproofing and breathability using membrane structures and manufacturing technologies different from those of Gore-Tex, and their price, performance, and durability vary depending on the product and intended use. Therefore, rather than simply assuming that a cheaper alternative to Gore-Tex offers the same performance at a lower price, it is necessary to examine the specific structures and technologies used by each material, as well as the actual performance they deliver in finished products. Furthermore, Gore-Tex is not resting on its laurels but continues to develop new membranes. Recently, products incorporating membranes made from expanded polyethylene (ePE) have emerged; this technology is leading to the development of products that are lightweight and thin while maintaining waterproofness, breathability, and wind resistance—all without the intentional addition of PFAS.
As we have seen, the core principle behind Gore-Tex—which keeps you dry in the rain while allowing water vapor from sweat to escape—lies in the membrane’s structure, which features extremely small pores. The microscopic pores in traditional ePTFE membranes prevent liquid water from passing through easily while allowing water vapor to escape. Combined with the DWR treatment on the outer fabric, a multi-layered fiber structure, and waterproof seam sealing, these features enable Gore-Tex products to deliver waterproof and breathable performance even more effectively. Among the drawbacks of Gore-Tex are its relatively high price and the fact that the performance of external treatments, such as DWR, is not permanent. However, performance can be maintained through proper washing, drying, and DWR reapplication, and the membrane itself continues to evolve, with technology expanding from ePTFE to ePE.
Even at this very moment, many people—from hikers to sports enthusiasts—are wearing clothing made with Gore-Tex. Just as Gore-Tex has become deeply embedded in our daily lives, the ability of a simple scientific principle to evolve into a useful technology for everyday use is likely due to the power of engineering—the discipline that understands scientific principles and applies them to real-world situations. Even the functional clothing we use without a second thought in our daily lives is underpinned by scientific principles such as the structure and properties of materials, moisture transport, and surface tension. Ultimately, Gore-Tex stands as a prime example of how scientific discoveries, when combined with engineering expertise, can make our lives more convenient and comfortable.
