How Membranes Work

In hunting and mountain wear, it’s widely understood that garments need to withstand cold winds and heavy rain. That’s why such gear is equipped with membranes – protective barriers designed to keep you dry. But how exactly do these “barriers” work?

 

It’s simple: membranes are made with microscopic pores that are many times smaller than a water droplet, so liquid water can’t pass through. However, these pores are still large enough to allow body vapor (sweat in gaseous form) to escape.

Wondering how small these pores are? Smaller than a single micron – that’s one-millionth of a meter.

 

Types of Membranes

Membrane fabrics are generally classified as 2-layer, 2.5-layer, or 3-layer constructions:

 

2-layer: A membrane is bonded to the inner side of an outer fabric.

 

2.5-layer: Similar to the 2-layer but includes a thin protective film on the inner side of the membrane, applied by spray or print. This improves durability and water resistance.

 

3-layer: Combines the outer fabric, the membrane, and a third inner layer – often a mesh or woven fabric. This inner layer protects the membrane from abrasion (especially at elbows, knees, shoulders) and enhances breathability. More on that in a moment.

 

Membranes can also be made from different materials. The most common are:

 

ePTFE (Expanded Polytetrafluoroethylene)

 

PU (Polyurethane)

Others are PU-based blends with materials like polyamide, polyester, or elastane.

 

Often, the fabric is treated with a Durable Water Repellent (DWR) coating. This is not a membrane, but an outer treatment that helps the surface repel water more effectively.

 

How Membranes Perform in Rain

When it rains or snows, water on the garment surface can block the pores, trapping moisture inside. In 2-layer and 2.5-layer garments, this can cause sweating or condensation when the body heats up.

 

3-layer membranes behave differently. Their inner fabric holds moisture temporarily until it can be wicked outwards once the rain stops or the fabric dries. This design reduces the risk of overheating and improves comfort in wet conditions.

 

Waterproof Ratings – Explained

To measure waterproofness, manufacturers test fabrics in labs by placing them under a column of water under pressure for 24 hours.

 

For example, a fabric rated at 10,000 mm can withstand the pressure of a 10-meter column of water over 24 hours without leaking.


Water Column (mm)  Protection Level Suitable For
0 – 5,000 mm  Low water resistance Light rain, dew, dry snow, no pressure
6,000 – 10,000 mm Moderate resistance  Light rain/snow, low pressure
11,000 – 15,000 mm  Good resistanceModerate rain/snow, moderate pressure
16,000 – 20,000 mm  High resistanceHeavy rain/wet snow, high pressure
20,000 mm +Maximum resistance Prolonged exposure to heavy rain/snow, extreme pressure
   

Breathability Ratings

Breathability is measured in grams per square meter over 24 hours (g/m²/24h). Similar to waterproof tests, breathability is tested from the membrane side to see how much water vapor can pass through.

 

Seam Taping

Most technical garments have taped seams using a waterproof tape to seal the needle holes and prevent leaks.

 

Membrane Performance After Washing

After washing, a membrane’s performance may decrease. This can be due to:

 

Cracks or abrasions in the membrane

 

Peeling of seam tape

 

Delamination (the membrane separating from the fabric)

 

Each membrane type reacts differently to wear and washing. That’s why proper garment care is critical to extend its life. Always follow the manufacturer’s care instructions.

 

The CSXP Membrane by Chameleon Hunting

At Chameleon Hunting, we use a high-performance 3-layer membrane with 20,000 mm+ waterproof rating. The CSXP membrane is a blend of polyurethane, elastane, polyester, and polyamide.

 

Thanks to its high elasticity, it won’t crack during intense movement or stretching. The third layer is a hygroscopic, quick-drying polyester that helps move vapor away from the body and protects the membrane from damage in high-stress areas (elbows, knees, shoulders).

 

All seams in our garments are taped for maximum waterproof protection.