Membrane in shoes – does it make sense?

Although opinions are divided, the magic stamp attracts. How much marketing and how much truth? We try to explain the.

A membrane in boots provides waterproofing, and that’s its main advantage. However, it is worth noting right away that the life of the membrane is shorter than the rest of the shoe, and there is no possibility of repairing or waterproofing it (not the membrane itself), as in the case of leather. We have to expect that the membrane will one day stop working.

Modern and lightweight hiking boots, in which protection from getting wet is provided only by a mambrane (fot. Salomon)

In shoes designed to be lightweight, there is no other way to provide protection from getting wet. A membrane is an ultra-thin membrane, lined or pressed onto a fabric, which is then used to sew a lightweight and flexible “sock”. This is a solution that can be used in any model of shoes.

A more traditional hiking shoe with a nubuck leather upper, which together with the membrane provides better protection against soaking (photo. AKU)

Want to learn more about different types of outdoor footwear and see which one will best meet your requirements? welcome:

Breathability – principle of operation

Breathability, which is the colloquial term for wicking evaporating sweat to the outside of the boot (or jacket, pants, etc.), is an essential feature of shoes, since feet sweat even in low temperatures during intense exertion. A membrane, while protecting against soaking, is supposed to help solve this problem. At least that’s the assumption.

A microscopic image of the PTFE membrane from an SEM microscope. The size of the spears is about 10 microns / Membrane in boots – does it make sense? (fot. Gore-ex)

Membrane has micropores. These are holes small enough that a water vapor molecule can get through, but a single water molecule can’t anymore. Thanks to diffusion, or basically osmosis, sweat evaporating from the foot can escape to the outside, as the molecules of the substance in the gaseous phase (liquid and solid too) strive for thermodynamic equilibrium. The phenomenon of osmosis is the penetration of particles through semi-permeable membranes. The difference in the concentration of water vapor (perspiration in gaseous form) on two sides of the membrane creates osmotic pressure, which causes the transport of water vapor from a medium of higher concentration to a medium of lower concentration, i.e. from the inside of the shoe to the outside.

Gore-Tex membrane in Surroung technology, that is, with holes in the sole to improve water vapor removal / Membrane in shoes – does it make sense? (fot. Gore-Tex)

For the sake of simplicity, we can say that in the case of a shoe and a sweating, heated foot inside, we have two systems striving for equalization. First, the temperature: warm air and warm vapor “want” to go outside. Secondly, humidity: water molecules in the air will move toward an area of lower humidity.

In view of the above mechanisms, two basic conditions must be met for the shoes to breathe:

• The humidity outside must be lower than inside the shoe,
• The temperature outside should be lower than inside the shoe.

The greater the differences, the faster the diffusion. However, even in ideal conditions (very cold and dry) during very intense exertion, the membrane probably won’t “do a good job” of letting evaporating sweat pass outside. In addition, for it to work as it should, the membrane together with the base material should be:

• clean: micropores sealed with dirt have no right to work,
• dry: the “large” water molecules on the base material of the membrane, will block the water vapor molecules trying to get out.

The second point is particularly important. Here also comes the issue of “membrane impregnation”. By impregnating the jacket, we make the laminate (2, 3-layer construction of the material from which the jacket is sewn, and inside of which there is usually a membrane), does not get wet and thanks to this, the membrane can “breathe”. Shoes are exposed to soaking much more (friction, compression), if water penetrates the first layers and enters the membrane sock, we still have waterproofing, but the membrane stops breathing. Therefore, whether with or without a membrane, shoes need to be washed, cleaned and waterproofed from the outside.

One of the possibilities of layering and location of the membrane in shoes (fot. Gore-Tex Performance Comfort Footwear)

The shortcomings of a membrane in boots concern breathability. Any barrier, even the best, is worse than no barrier at all. Ultimately, however, most of us opt for boots with a membrane. First of all, everyone prefers to sweat than to get wet or soaked several times (sweat – warm, water – cold). Second, the choice among models with a membrane is much greater. For the time being, there is no better alternative either. Although the breathability of the membrane leaves a lot to be desired, if you want the shoes to be light and soft, yet waterproof (and therefore not made of thick leather), you reach for the membrane.

Even though I know the drawbacks of using a membrane in boots, I still chose approaches with a membrane. Where I use them, the weather changes quickly, so I’d rather sweat a little when it’s warm than freeze when I’m caught in a storm (phot. outdoormagazine.en) (fot. outdoormagazine.pl)

Michal Gurgul

PS. Membranes used in jackets and other garments perform very well, much better than in boots. Are more durable (socks and shoes wear out the fastest), are easier to clean and waterproof the material they are applied to, are more likely to provide a good level of breathability because they are not as „hidden” as with shoes.