Whenever you research outdoor gear, you will hear about Gore-Tex. But what is Gore-Tex, how does it work, and why do you need it?
Gore-Tex is a brand name for a waterproof, windproof, breathable, durable fabric, designed by WL Gore & Associates in 1969. A “breathable” fabric is one that stops liquid water getting in, but lets water vapour out. It's a mainstay amongst the best waterproof jackets, although a number of brands have their own versions.
GoreTex: why it matters
By dint of being waterproof, Gore-Tex is also windproof. But what’s the point of breathability?
As we move during hiking, skiing or other outdoor activity, we get warm and perspire. That means our bodies constantly emit water vapour. If we wear a fully impermeable outer layer, that water vapour gets trapped inside and condenses into water droplets.
That is exactly what happens when we wear a plastic pocket-poncho or similar. It keeps us dry from rain, but we quickly get sweaty, and our base layers become damp. This starts off as just being uncomfortable, but if we are somewhere remote, it can also become dangerous.
When the water vapour from perspiration cannot get out, the wearer cannot cool down, which creates a vicious cycle of increased perspiration. That leads to overheating (hyperthermia) and dehydration. Wet layers also tend to lose their insulating properties, so, if an active person stops moving and stops generating heat, they can get cold very quickly, leading to hypothermia.
As well as this breathability, Gore-Tex is durable, which stops it ripping like a poncho. It can be worked and shaped into different garments, and is even used for medical applications.
Lots of clothing companies use Gore-Tex in their products. But, since the original patent expired, some companies have created their own breathable, waterproof fabrics, using similar technology.
How does GoreTex work?
Gore-Tex is made from PTFE, which is better known by its trademark name: Teflon. When PTFE is stretched very quickly, it creates a microporous structure that is 70% air. The pores in this membrane are around 20,000 times smaller than a water droplet, so liquid water cannot pass through them. But the pores are 700 times larger than a water molecule, so water vapour can get out.
The Gore-Tex membrane is bonded to an anti-abrasion outer layer to protect it. This outer layer then has a Durable Water Repellent (DWR) applied to it. The DWR stops the outer layer becoming saturated with water, which would prevent water-vapour getting out, reducing the breathability and causing damp patches on the inside of the fabric.
This basic construction is a '2-layer' waterproof fabric. If an inner layer is also bonded to the Gore-Tex membrane, it creates a more durable '3-layer' fabric.
How to care for your GoreTex clothing
Over time, the outer-layer’s DWR can get worn down, leading to saturation, reduced breathability and damp patches. This makes it seem like your Gore-Tex fabric has lost its waterproofing. But if you tumble-dry or iron the garment, the DWR is re-invigorated, and your garment becomes breathable again.
Gore-Tex now has several sub-ranges, including Gore-Tex Pro and Gore-Tex Infinium. Check out this article to learn more about the different Gore-Tex fabrics.