Last Updated on 26/01/2022
It keeps you dry and lets you breathe, but what is Gore-Tex made of? Gore-Tex is a membrane made from a stretched polymer that has over 9 million pores per square inch. These pores are small enough that water droplets cannot fit through but large enough that condensation inside can evaporate.
If you spend enough time outside, you get used to battling the elements and braving the rain. A quality set of waterproofs is essential because when you’re really out in the wild, the weather can change in an instant. But with so many different brands to choose from how do you differentiate Gore-Tex from eVent fabric or the many others?
Gore-Tex has established itself as one of, if not the, highest quality waterproofing on the market. But just what is Gore-Tex and is it worth the money? In this article, we’ll take a look at how it’s made and what it is used for.
What is Gore-Tex?
Gore-Tex is a breathable, waterproof membrane that keeps you dry from the outside and from the inside. We will get into the technical details shortly, but for now, think of it as an advanced fabric layer that is glued between the lining and the outer of a waterproof garment.
Gore-Tex clothing is waterproof, windproof, and breathable. The membrane has more than 9 million pores per square inch, which we will look at further on in the article. In short, these pores allow steam and sweat to escape from your body without allowing water particles through the other way.
What is Gore-Tex Made of?
Gore-Tex is made from a stretched polymer. Well, what is a polymer, you might be wondering? Synthetic Polymers like polypropylene and PTFE’s are thermoplastics which means they soften when heated and all have similar chemical properties. By stretching polytetrafluoroethylene (PTFE), the original creator of Gore-Tex, Bob Gore, inadvertently invented a whole new polymer, ePTFE.
This expanded PTFE, also known as Teflon, is a porous material, though the pores are minuscule. Each square inch of ePTFE has more than 9 million pores in it. These pores are so small that raindrops cannot penetrate them, but moisture is able to pass through them in the other direction.
How is Gore-Tex Made?
But what about specific Gore-Tex fabric? How is that polymer turned into the waterproof and windproof jackets and pants we wear on the mountain? Gore-Tex fabric tends to come in three main styles, 2-layer, 3 layers, and Z-layer that all have different compositions and are made in slightly different ways.
2 layer Gore-Tex has the Gore-Tex layer bonded directly to the outer material of the jacket. With 2-layer Gore-Tex, the inner is free from the outer layer and can move independently. This means that you can add insulation or internal liners to the jacket and maintain a waterproof outer.
3-Layer garments sandwich the Gore-Tex layer between an outer and an inner fabric. This creates a garment that is hard-wearing in all weathers and can be lightweight and reduce bulk. It does often also mean that the jacket feels a little heavier duty, such as mountaineering shells.
By sandwiching the Gore-Tex layer, the fabrics are unable to move against one another. This increases the durability of the jacket as the different layers don’t rub against one another, which causes wear points.
For Z-layer Gore-Tex, the membrane layer is bonded to a lightweight fabric and allowed to float between the inner and outer layers of the jacket. This reduces the number of seams needed through the membrane, which we will discuss shortly.
Z-layer Gore-Tex is often used in winter jackets. Fewer seams allow for more design freedom and the floating membrane layer works well with insulation or liners.
Regardless of how effectively you try to use your waterproof membrane, a jacket or waterproof pants require some stitching. The holes that a sewing machine makes are enormous when compared with those in the membrane.
Okay, so a thread will fill some of that space, but a thread isn’t waterproof. Companies will tape the inside of a seam with waterproof tape, usually heat-treated into place, to stop water from entering through the seams.
How Does Gore-Tex Work?
Gore-Tex is a membrane that has more than 9 million tiny pores in a square inch. These perforations are almost 2000 times smaller than your average water droplet molecule, but 700 times larger than those of water vapor.
This means that while raindrops can’t get through the membrane, your jacket or pants will breathe as you sweat on the trail. Most outer layers of Gore-Tex jackets are treated with a Durable Waterproof Repellant (DWR) coating. This means that water beads and runs off, improving the breathability of your jacket.
If your DWR layer wears off, the outer layer of your jacket will become clogged with water droplets and breathe less effectively. In this scenario, you may end up soaked from the inside out if you don’t replace the DWR coating.