Gore-Tex is a name synonymous with waterproof-breathable jackets. But if you’ve wondered What does Gore-Tex actually do? … this Explainer is a good place to start.
![gore tex jacket](https://s3.amazonaws.com/images.gearjunkie.com/uploads/2016/07/gore-tex-jacket-700x700.jpg)
In 1969, Bob Gore was experimenting with a chemical compound called polytetrafluoroethylene by rapidly heat-stretching the polymer. Rather than snapping, the material unexpectedly stretched 800%, forming billions of micropores per square inch, each about 1/20,000 the size of a water droplet but 700 times the size of water vapor.
Turns out, the porous structure blocked water but allowed vapor to pass through. The invention, patented as Gore-Tex by W. L. Gore and Associates, became a juggernaut and standard in the outdoor market, popularizing a whole new category of jackets called waterproof/breathable (they keep water drops out, including rain and snow, but let vapor from sweat escape from the inside).
With booming popularity over many decades, the name Gore-Tex became synonymous with waterproof/breathable as many new players entered the field. Even today, the Gore-Tex brand is often used to refer to waterproof/breathable jackets in the same way Kleenex refers to facial tissue.
![Gore-Tex membrane viewed with an electron microscope](https://s3.amazonaws.com/images.gearjunkie.com/uploads/2016/07/gore-tex-membrane.jpg)
Waterproof Breathable
Waterproof/Breathable Limitations
![Water beading on Gore-Tex fabric](https://s3.amazonaws.com/images.gearjunkie.com/uploads/2016/07/water-beading-on-gore-tex-fabric.jpg)
Waterproof/Breathable Fabrics, Quantified
- Hydrostatic head is the measurement of a material’s waterproofness. It measures in mm how tall a 1-inch2 column of water must be to breach the material. We recommend a minimum waterproof rating of 5,000mm to be considered truly waterproof.
- Moisture Vapor Transmission Rate (MVTR) measures the rate at which moisture moves across the material in grams/meter/day. We recommend looking for an MVTR rating of 10,000 or higher for more active pursuits.
- Resistance to Evaporative Heat Transfer (RET) measures how breathable a garment is, with lower being better for more aerobic activities. Gore-Tex Pro has a RET of less than 6; Gore-Tex Active, which is more breathable, is less than 3 RET.