The resurgence of Water Repellency Testing

We have seen an increase in athleisure for many years now. The sportswear industry has influenced mainstream fashion, and innovations in technology has led to improvements in functionality.

For outdoor wear in particular, the onset of a global pandemic has increased demand even further. With the long-term closure of gymnasiums, swimming pools and exercise classes, more and more of us are heading outdoors to exercise. More people are holidaying in their home country as well, which for a lot of us means swapping swimwear for raincoats and walking trousers. With this increase in demand comes more rigorous performance testing to ensure these garments perform as they should when exposed to the elements.

It is also becoming more common to select accessories such as backpacks, for their water repellent or waterproof qualities. Another consideration for brands and manufacturers can often involve more feature specific testing to establish, for example, what role seams, zips and pockets play.

Consumers expect comfort from their garments. Comfort is influenced by fit factors as well as fabric properties such as stretch and recovery, and thermal and moisture management properties. But for outdoor wear in particular, comfort is about finding a balance between keeping water out and letting sweat escape.

Safety is arguably the most important feature that users can expect from their performance garments. There are risks involved with getting the breathability of water repellent fabrics wrong, mainly that they can trap sweat and cause the wearer to overheat. This might not seem like an issue for a quick walk around the park, but for wearers on long hikes this could cause serious health risks.

To understand the testing we need to undertake, it is important to understand the make-up of a garment, and the role that layers play.

In sportswear, and especially outdoor wear, a three-layer clothing system is often advocated, with each layer in the system performing a different function that complements the whole for maximum comfort.

A layering system typically includes:

• Base layer 

• Mid layer

• Outer protective shell layer 

An effective outer layer should have a high level of water resistance as well as a high level of water vapour permeability (breathability). How this layer is constructed plays a significant part in this.

This is where the challenge of the outer layer comes in – creating a fabric which provides good water resistance is relatively simple, but doing this while maintaining breathability is a more complex process, as these two properties have an inverse relationship in typical textiles. A thorough testing regime can prove the balance between these properties have been met.

Testing water repellency

Water repellency is tested by spray methods, using instruments such as the Bundesmann or Spray Rate Tester, where water is run over the surface of the fabric and the repellency is visually graded.

For the Bundesmann method, in particular testing to ISO 9865, the test instrument generates artificial rainfall to simulate the real life conditions the end garment will be used in. Here three aspects of water repellency are measured:

• Surface water repellency is visually assessed,

• Resistance to water absorption is evaluated by weighing the specimen, and

• Resistance to water penetration is determined by collecting water that has passed through the sample.

As with any testing, there are certain parts of the process to look out for, which can have an impact on your results.

Professional tips in testing:

• Clamping the fabric incorrectly can cause a variance in results.

• Timing is everything – be ready to assess as soon as the test finishes.

• Condition your samples in accordance with the standard.

• Water temperature is important and should be recorded.

• The Bundesmann must be run for 15 minutes prior to testing to guarantee water flow is consistent.

Sustainability

Traditionally the Bundesmann test requires a lot of water, which can be an issue for apparel brands and manufacturers who are tackling issues of sustainability.

The UN Partnership on Sustainable Fashion found that fashion is responsible for nearly 20 per cent of the world’s wastewater, and 10 per cent of global carbon emissions, so there is a lot of pressure to be cleaner, more efficient, and ultimately sustainable. Although testing plays a small part in the process, there are significant savings to be made in water usage during testing.

We recently conducted a small research project into the efficacy of water recirculation on our Bundesmann testing instrument.

A typical Bundesmann water repellency tester that runs for 8 hours per day, five days per week, is consuming 3,360 litres of water. It is plumbed into the mains and drained directly after a single fall onto the specimen. Recirculating the water would reduce usage, but we had to establish there would be no detrimental effects to testing when doing this.

Concerns:

• If the fabric sheds when being washed, and synthetic fabrics in particular shed a lot of microplastics, would this shedding stay in the water and impact the next round of testing?

• Would it stick to the next specimen being tested and give a false impression of water repellency for a garment that would then fail when worn?

We conducted significant testing, in-house and using an external laboratory, to verify that the results would be accurate regardless. The test results concluded that there was consistency from start to end, and by confirming this, we were able to calculate the savings our recirculation unit could offer.

• An 8-hour working day’s use of the TruRain Bundesmann recirculation system sees 83 per cent total cost savings in energy consumption and total running costs.

• There is less waste: 99 per cent less water is used during testing alone – if you did 150 tests a week, your water consumption drops from 2,100 litres to just 23 litres.

• Additionally, it is accurate, safe, and reliable: Through the use of an effective Water Safety Plan, health and safety can be maintained.

We also found that by using the recirculation unit, we were able to maintain the temperature of the water much easier. The percentage of water absorbed by fabrics can increase as the temperature increases, so this is important to control for consistency of results.

Proving Water Repellency

With an increase in demand for water repellent clothing, and the subsequent increase in the popularity of Bundesmann testing, understanding and implementing repeatable testing is crucial to substantiate any claims made about a garment. The challenge for retailers and manufacturers is to meet and exceed consumers’ expectations for comfort and performance, and water repellency is one part of the puzzle for achieving this.

About James Heal, USA

James Heal USA is a leading supplier of premium textile testing instruments and test consumables in the North American market.

As a part of the Physical Properties Testers (PPT) Group, a multinational holding company, we are committed to innovation and the development of test instruments, which combine high quality and precision with innovation and industry-leading technical expertise.

This ensures our customers achieve test results with the highest levels of accuracy, reliability and reproducibility.

We have a high level of expertise and knowledge, from the people who design our instruments to our materials technologists who run our laboratories.