As a detail obsessed, outdoor enthusiast, card carrying gear nerd, I find myself writing about GORE-TEX a lot. It's quite possibly one of the most common materials in the products I've used, abused, and reviewed. While there is deep appreciation for what this product does and how it either improves the performance of apparel or how it even makes some activities possible, it's quite surprising how many misconceptions or misunderstandings there are about what GORE-TEX actually is. So for that reason I thought there may be a need to write about it and clarify exact "What is GORE-TEX?"
First, why are there so many misconceptions about GORE-TEX? The foremost reason has to be that W.L. Gore and Associates, who manufacture GORE-TEX, have done such an amazing job of branding their product. This is evidenced by the way people use the brand name in reference to products which it is used in. This is similar to when people say 'Rollerblades' when they are referring to inline skates, or Kleenex when speaking about tissue paper. The official term for this phenomenon is called a proprietary eponym. When this happens with GORE-TEX, it's usually someone saying "my GORE-TEX jacket", or "my GORE-TEX gloves" and so on, and so on. It's become so prevalent a habit that even if it's not exactly a proprietary eponym, it may as well be.
What is GORE-TEX?
In the quest to clarify what it really is, let's first clear up what GORE-TEX is not. It is not a;
- Material, fabric or a textile
- Knit, or a weave
- Chemical treatment
- Boot, jacket, glove, or hat. In fact it is not any piece of apparel or equipment
Alright then, so what exactly is GORE-TEX? It is;
- A brand
- A Product first introduced to the market in 1978
- A membrane
- UV Resistant
What is GORE-TEX made of?
A somewhat basic but still technical answer to this question is that at the heart of GORE-TEX is a 0.01mm thick microporous membrane that is made of expanded Teflon (polytetrafluoroethylene) more formally known as ePTFE. This is a linear polymer, a large single chain molecule, that consists of flourine (atomic no. 9) together with carbon (atomic no. 6). Carbon is the 15th more universally abundant element and Flourine is the 24th most abundant.
Resources: GORE Brand's 'What is GORE-TEX
What does GORE-TEX look like?
My best description would be that it looks a bit like a plastic film. The best way to directly see GORE-TEX is to look on the inside of a GORE-TEX 2L such as the GORE-TEX Pro Shell where a single outer layer has the ePTFE membrane laminated to the inside. It looks like a plasticy coating.
How is GORE-TEX made?
What makes GORE-TEX really special is the 'e' in ePTFE. This refers to the expansion process in which the fibers are rapidly and forcefully stretched to create their linear formation. The expansion process which was discovered by, Bob Gore, and then innovated by W.L. Gore & Associates, is what lead to their signature polymer. The resulting chemical bond between the flourine and carbon is remarkably strong and is resistant to harmful chemical contact (ie. bug spray.) When the GORE-TEX membrane is laminated to an inner and or outer material it then becomes a Gore Fabric.
Are the different types of Gore Fabrics?
Yes, there are 3 basic types of Gore Fabric. What is common between all three types is that they each begin with the breathable membrane and then are bonded, through lamination, with an inner and or outer fabric.
The first type of Gore Fabric is a 2-layer construction consisting of the GORE-TEX membrane and an outer fabric. This is the simplest and generally the lightest of the current types. A new variation of this first type is now available in the market with the membrane on the outside of the garment. The 2-layer GORE-TEX is in lightweight applications or for warm weather activities.
The second type is the 3-layer construction with the GORE-TEX membrane bonded to a soft faced inner lining as well as a more durable outer material. The 3-layer construction is most often found in equipment for colder activities.
Finally, the third type is called "Z-liner" This type is similar to the 3-layer in that it has both and inner and outer layer as well as the GORE-TEX membrane in between, but the inner layer is free floating and not bonded to the membrane. This is a good choice for constructing garments like winter outerwear where you want to place down or insulation between the inner layer and the membrane for warmth.
How does GORE-TEX work?
When the PTFE is expanded, the space between the polymer strands expand to create pores. These pores are small enough to allow water vapour such as perspiration to pass through, but are far too small for water drops such as rain to pass through. To help put that into context, think of it this way. Imagine water vapour is like sand and if you pour that over a screen mesh it will flow through. Now imagine water drops are like pebbles which are small, but still too big to pass through screen mesh. So in a sense, GORE-TEX works like a one way door that allows water vapour to pass through but prevents rain from making its way through. This is the reason why GORE-TEX can be water proof but remain breathable* at the same time.
Tip: Remember, breathability of a fabric is not the ability to flow air but actually the ability to move water vapour.
How is GORE-TEX different than WINDSTOPPER?
This is a bit of trick question because both of these W.L. Gore products are PTFE membranes made through an expansion process. But the key difference is that WINDSTOPPER is stretched further to create larger pores than those in GORE-TEX.
WINDSTOPPER allows larger water vapour or greater volumes of smaller water molecules to move through. This increases its breathability while still maintaining its windproof'ness. WINDSTOPPER is simply a variation created to server different functional applications.
Resource: What is WINDSTOPPER?
Can you buy GORE-TEX or Gore fabric?
The simple answer is no. Only approved and licensed partners can buy Gore Fabrics from Gore. These licensed manufacturers purchase the fabric direct from W.L. Gore & Associates and then must have their products tested and approved before going to market.
Are there environmental or health impact concerns to PTFE based products?
According to W.L. Gore and Associates, the PTFE polymer which is used to make the ePTFE membrane is non-toxic, bio-compatible, non soluble (will not end up in water ways and oceans), and does not degrade to become perfluorinated chemicals/compounds (PFC.) Any claims to environmental impacts due to the manufacturing of the ePTFE membrane are countered by W.L. Gore & Associates by reason that the membranes help extend the lifespan and performance of the products they are used in, therefore balancing the environmental impacts of production.
But it should be fairly stated that while yes the ePTFE membrane is both highly breathable and waterproof, the water repellency of the outer material is actually thanks to Durable Water Repellency (DWR) treatments made from PFCs.
Since DWRs are commonly used in Gore fabrics, the topic of PFCs is important to explore. PFCs, particularly C8 long-chain PFCs, are considered harmful to the environment. These DWR chemical treatments have been identified as source of environmental contamination through off-gasing which can be bio-accumulating. Led by the Chemicals Management Working Group (CMWG), of which W.L. Gore & Associates is a founding member, many outdoor brands have put action plans in place to transition from C8 long-chain PFCs to much lower impacting C6 short-chain PCFs.
Resource: Arc'Teryx PCF in Outdoor Products
So that's what the research literature says. While researching this article I wanted to provide a fair and balanced report so I reached out to a former climbing partner, Craig Butt, who is now Product Application Specialist at Sciex, and former Research Scientist at Duke University and whom holds a PhD in Environmental Chemistry from the University of Toronto. Here is his take... Definitely a balanced perspective to spark conversation and consideration.
"Waterproof clothing is made with fluoropolymers to provide that water resistant & breathable property that we desire. However, the fluoropolymers contains volatile chemicals (e.g. FTOHs, FTACs) that off-gas from the clothing. We know that these volatile chemicals can break down in the body and the atmosphere to form chemicals that are very persistent in the body (i.e. half-life is 3-5 yrs). What's the human health effects of these chemicals? Hard to say but there is some evidence that they cause immune system suppression (specifically they reduce the efficacy of vaccines). However, one significant unknown is if these chemicals in the waterproof clothing are major sources of fluorochemicals to the body. In other words, how much of these chemicals travel from the clothing into the body and is this sufficiently high to cause harm."