The Science of Water Resistant Fabrics

MANY people use the phrases ‘waterproof’ and ‘water resistant’ interchangeably but the two do not mean exactly the same thing.

And this is important when it comes to choosing the right fabrics for the purpose you need them for, such as upholstery.

Waterproof is easier to explain as it means literally what it says – the fabric is impervious to water. Water – or other liquids like coffee or wine or soda – will simply run off the fabric and be absorbed in any way.

This can be ideal for things such as outdoor furniture or upholstery in places where it is going to get wet such as a boat. It is also very easy to clean as it can simply be wiped down and your cleaning product is not going to get absorbed or leave traces.

But for a fabric to be completely waterproof it is also going to be completely airproof – the textile is simply solid, and nothing can pass through it under normal conditions, such as rubber or plastics. This means there is no breathability in the fabric at all, so if water does penetrate through a weak spot such as stitching in a seam, where holes have been made, then it is going to stay there.

That means the little water that does get through into an under layer like foam is going to stay damp, and that dampness can quickly become a breeding ground for bacteria or molds.

The other key issue with a completely impervious barrier fabric is one of comfort – without an element of breathability it can become uncomfortable to sit on for long, especially with bare skin in contact and in more humid climates as your own body’s moisture is going to pool on it and you are going to become sweat and sticky quickly.

For these reasons, many fabrics used in upholstery – especially in outdoor furniture but also indoor or commercial furnishings – people often prefer a water-resistant or water repellant fabric.

These fabrics are not entirely waterproof – if they get saturated water will pass through the surface, but with the technology behind many of the fabrics, under normal use, the liquid is more likely to not be absorbed or at least give you a good time interval to clean it up before it is absorbed.

The extent to which a fabric is water-resistant depends on the technology of the fabric and the make-up of its fibers, especially with modern synthetic polymer-based material – some fabrics will offer more resistance to liquids than others.

The key factor behind resistant fabrics is that they are breathable – which is a two-way process, as although some moisture could pass through the fabric, it can also pass out again as it dries.

Water-resistant fabric does not get damaged by water. If a fabric is truly water repellant, the liquid will bead on the surface and runoff, but if it is water-resistant the fabric will dry off.

There are several characteristics of fabrics that help determine whether it is water-resistant, the key one being the material itself. Man-made fibers are especially noted to be very good at resisting water with very low absorbency rates as they prevent water soaking in at a molecular level, but some natural fabrics can also be good at stopping water ingress, and of course, they can often be blended to combine different characteristics.

Further, some fabrics themselves may not be especially good at resisting water but can be treated with chemical solutions after being woven, and it is the solution rather than the fabric that goes to work, filling the natural gaps in the weave and forming a protective coating on the fabric to act as a barrier. These solutions are often made from mixtures of rubbers, waxes, and polyvinyl chloride.

And the weave of the fabric itself will add a degree of water resistance – the closer and tighter the weave, and the higher the thread count, the smaller the holes and the more resistant it is – this is measured in units called a denier.