What is Gore-Tex really all about?
If you have ever tried to fix a leaking tap you have probably used what is commonly called ‘Plumbers tape’ or ‘Teflon tape’. This thin, pliable white material that blocks moisture escaping through plumbing thread is made of a substance known as Polytetrafluoroethylene (PTFE). This substance is the same building block that makes the magic of Gore-Tex happen.
Bill Gore, an American chemist realised as early as the 1950s that when rapidly stretched under the right conditions, PTFE took on some amazing properties (and in this state the material is said to be ‘expanded’ hence ‘ePTFE’). This led to the development of Gore-Tex fabric (patented in 1978) as well as numerous other applications for ePTFE including guitar strings, vacuum cleaner filters, air sacs for bagpipes, linings for casts on broken limbs, electrical cables, dental floss, sewing thread, organic waste treatment membranes, industrial ropes, insect screens, filtration units, gaskets and sealants, even heart valves, skin grafts and space suits.
In Gore-Tex fabric the ePTFE layer, known as a ‘membrane’ acts like a second skin by preventing wind and water (rain) from getting through whilst allowing moisture vapour (sweat) to escape. Garments made from Gore-Tex are therefore termed ‘windproof’, ‘waterproof’ and ‘breathable’. The rigourous testing and quality controls imposed by the company ensure that all garments are totally sealed and thereby apply an unique guarantee on any product made with Gore-Tex fabric - “Guaranteed to Keep You Dry”.
Despite the fact that there are now many alternative fabrics that claim similar properties, the excellence in quality control, combined with a highly functional product has led to the name Gore-Tex being widely used as a layperson’s synonym for almost any high quality rainwear.
How does it really work?
Nowadays there are many different forms of Gore-Tex fabric available such as Paclite, Soft Shell and XCR but all follow the same basic principles.
When examined under a microscope the ePTFE membrane resembles a three-dimensional net constructed of rough, interconnected fibres. The spaces between the fibres are called ‘pores’ and because the pores are so small the material is known to be ‘microporous’. One square centimetre contains 1.4 billion pores (give or take 3 or 4) and it is the size of the pores that is the key to the membrane’s ‘breathability’. The pores are thousands of times too small to allow liquid water to pass through yet hundreds of times larger than a water vapour molecule. Heat generated by the body creates a slight pressure differential that forces water vapour (sweat) through the fabric with such efficiency that this will occur even when the outside of the fabric is fully submerged in water. To prevent pores in the ePTFE membrane clogging with oils such as sunscreen and body oils a permanent oleophobic (oil-resistant) coating is applied to the membrane during its manufacture.
In Gore-Tex fabric the ePTFE membrane, which is very thin and fragile, is protected from puncture and abrasion on both sides like the meat in a sandwich. The outer ‘shell’ fabric is a lightweight but strong synthetic material (usually nylon) that is laminated to the membrane and does not impede the breathability of the material. (Note: in some Gore-Tex products such as LTD-Liner and Z-Liner the shell fabric is not laminated). In a ‘3-Layer’ fabric a lightweight nylon, or ‘Tricot’ mesh is laminated to the inner side of the membrane completing the sandwich. ‘2-Layer’ garments still have a liner material but it is not laminated to the ePTFE membrane so it is not quite as durable as, but usually cheaper than, a 3-layer garment. Various other coatings and fabrics are applied to the inner face of different types of Gore-Tex materials, but all with the function of protecting the membrane.
Even a puncture the size of a pin jeopardises the integrity of the membrane but a garment must be stitched together (or in some cases it can be welded) creating lines of holes from the needle. To prevent moisture entering these holes and the gap between the two pieces of fabric, Gore-Tex waterproof garments are ‘tape-sealed’ on the inside of the fabric. This time-consuming process ensures you stay dry while undoubtedly adding to the price tag.
When doesn’t it work?
Your skin is always releasing moisture, whether you are underwater, running a marathon or reading this page. If you wrap cling-wrap on your body you will feel clammy almost immediately. When your skin releases more moisture than can evaporate you feel like you are ‘sweating’. Most of the time a cotton t-shirt will allow your sweat to pass through it and evaporate but even a cotton t-shirt can become saturated. It is no wonder then, that a ‘breathable’ fabric like Gore-Tex, just like your skin, has its limitations.
Gore-Tex garments will keep you comfortable in a wide range of climatic conditions but it is important to note that Gore-Tex is not an air conditioning system and by stopping the wind from evaporating the sweat from your skin moisture will build up between your skin and the garment. Cleverly manufactured (and marketed) clothing ‘layers’ are designed to allow the moisture to easily ‘wick’ or move through the clothes you are wearing and pass through the Gore-Tex.
When exercising - walking, running, skiing, climbing et cetera - even in cold conditions it is possible to ‘max out’ Gore-Tex’s ability to wick moisture. Many Gore-Tex jackets allow for increased ventilation with features such as zips under the arms or vents built into the back. Ultimately, like the cotton t-shirt, Gore-Tex can ‘wet out’ or not be able to keep up with amount of sweat your body is generating. If you are wearing Gore-Tex while walking in a tropical downpour you may end up just as wet with sweat as you would from the rain.
Will it work for you?
Given its position in the market, the manufacturing techniques and the quality of the product, Gore-Tex will always be a relatively expensive product. There are many other ‘waterproof and breathable’ garments available so is it really worth your hard-earned cash?
Gore-Tex garments tend to last a long time if well cared for - many jackets are still going after 20 years which is much longer than most people would own a car. They are covered by a warranty and back-up service (internationally) that is hard to beat.
If you are likely to need protection from rain and wind then Gore-Tex garments are probably the most efficient solution to your problem. Be flexible enough with your entire clothing system that you can add or remove layers to increase or decrease insulation and accept the fact that if it is hot or you are exercising you may need to ventilate or simply remove your Gore-Tex.
If you would like to know more about how Gore-Tex products can work for you contact Outdoor Link and we’ll help you sort through which type of Gore-Tex and which garment will suit your needs best.
