DWR coatings – Blessing or a curse?

23. October 2018

Category

DWR stands for “Durable Water Repellent” and refers to a coating that is added to fabrics used for functional clothing and footwear. Thus, DWR is not a name for a specific material or system, but merely a description of a certain property. However, there are chemical and technological differences between the various treatments that manufacturers provide.

What properties does a DWR have?

If you feel like water is entering your rain coat, firstly check the DWR coating before you do anything else.

If your barrier against water seems to have failed you, check the DWR coating first.

For quite a long time, I had been under the impression that clothing sold as breathable and waterproof automatically had a durable water repellent coating. But, reality set in pretty quickly when I noticed the outer fabric of my Gore-Tex jacket had become saturated with water, leaving me to feel cold and clammy after relatively few uses. I immediately thought the membrane had been damaged, leaving the jacket leaky and no longer waterproof.

Fortunately, I was wrong – the jacket was still completely waterproof and otherwise in tip-top shape. The only thing was that the DWR treatment had lost its integrity, as these coatings are known to do over time. The reason why these coatings are so important is that they form the very first exterior barrier against water on the majority of functional garments. True, laminates and membranes do keep water at bay, but what they cannot do is keep water from penetrating into the outer layer of fabric. Once the water has coated the outside of the fabric, the material not only becomes wet but also loses its breathability. This is known as “wet out”.

A DWR treatment prevents the water from flowing together by keeping the fibres and the surface of the fabric very smooth. It then forces water to bead up and roll off the surface of the fabric instead of being absorbed by it. This can be achieved in a variety of ways. For example, in Gore-Tex materials, the treatment penetrates the fibres and reduces the surface tension of the outer fabric, causing the water to bead up and roll off rather than be absorbed.

However, these treatments quickly lose their effectiveness as a result of general wear and tear caused by dirt, oil, detergents and frequent use. The term “durable” should thus be taken with a grain of salt. The good news is that DWR treatments can be reactivated or restored quickly and easily, but we’ll talk about this in more detail a little later.

It’s worth mentioning that DWR treatments are not “waterproof”, but only “water-repellent”. It cannot withstand heavy or continuous rain by itself – it needs the support of a membrane and taped seams.

What is a DWR treatment?

You can find out how a DWR works just about anywhere, but it’s rare to find any info on what kind of substances and technologies are used for it. The lack of info is most likely due to the simple fact that you would have to do a deep dive into the world of industrial processes and technology and deal with a large number chemical substances:

Depending on the requirements for washing, cleaning and weather resistance, paraffin and wax emulsions as well as film-forming silicones and fluorocarbons, which provide durable protection, are used as DWRs. (…)”

For the most part, the finishes have been mainly polyfluorinated or fluorocarbon-based (PFC) because fluorocarbons are the most effective at repelling dirt and water. In the outdoor industry, there are two fluorinated compounds worth mentioning, namely perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA). Since not just PFOA and PFOS, but all fluorocarbons are now considered to be harmful to the human body and the environment, more and more manufacturers are looking for alternatives. Some alternatives work – simply put – on the basis of hydro and fatty acids (aliphatic carbon acids). You’ll find more about PFCs and the search for alternatives in the section on the environment.

Applying a water repellent to a fabric can done using various methods. The best known is the wash-in method by which the fabric is soaked in the DWR treatment. A new, more precise method is the spray method.

Reactivating or renewing a DWR treatment

A close-up of the DWR water-shedding ability.

A prime example of a DWR’s water-shedding abilities.

As already mentioned, “durable” does not mean “eternal”, so a DWR will inevitably have to be reactivated or replaced with a new one after frequent use. It’s really easy to find out which route you should take: sprinkle a few drops of water on the garment and see if they bead up. If it does, your DWR is in tip-top shape.

If the water is partially absorbed, one should first try to reactivate the old treatment. After washing your garment according to the manufacturer’s instructions, dry your garment using warm air only. You can do this either by tumble drying it on a warm gentle cycle at 60°C, by using an iron (no steam; no direct contact with the garment, but with a cloth in between) or by using a hair dryer. The heat should be applied for about 20 – 30 minutes. Afterwards, test your garment’s DWR again as described above. If it works, you won’t have to reactivate until the next wash.

If the water droplets are absorbed by the fabric, it’s time to apply a new DWR treatment. You have two options: either the wash-in or spray-on method. Regardless of the method you choose, the garment should be dry and clean before you apply the treatment.

If you opt for the wash-in method, it is important to be sure that the detergent drawer in your washing machine is clean. Then add the manufacturer’s recommended dose of the wash-in product and wash the clothing at 40°C on a gentle cycle. Then, depending on what the manufacturer recommends (see tag), either line dry or tumble dry at the lowest level.

The problem with the wash-in method is that the inside of the garment is coated as well, which can have a negative effect on the breathability of the fabric. There are different reactions depending on the membrane and the textile blends. Sometimes, manufacturers recommend having the garment treated by a professional cleaning service. Although this has the advantage that you don’t have to handle with any chemicals and it may result in a durable coating, the breathability problem remains.

The spray-on option may expose you to chemicals, but it has the huge upside that you can distribute the treatment only on the outside of the garment. In addition to treating the outer fabric, you can also apply it to particularly sensitive areas such as the seams, cuffs and shoulders. In the world of water-repellent sprays, only pump sprays do not use harmful aerosols as a propellant. Still, you should only use these sprays outside in a well-ventilated area and try to inhale as little as possible.

Soft shells are another garment with DWR coatings that need to be renewed from time to time. For this purpose, you can use Toko and Nikwax water repellent sprays. These wrap around the fibres like a water-repellent tube without stiffening the fibres.

You can find out more about wash-in vs. spray-on products as well as renewing the DWR finish on your garment in our guide to properly reproofing your waterproof jacket.

Also for shoes a DWR coating is neccessary.

Did your shoes take a dip in a river or did they land in mud? Well, hopefully the DWR is still in good shape!

When it comes to applying a new DWR to shoes, your only option is the spray-on method. Grease, oil and wax almost always ruin the breathability of the fabric. However, not every spray is suitable for every shoe, so once again, it’s definitely worth consulting the manufacturer’s care instructions and following them as closely as possible.

Here’s one more tip: Don’t get your hopes up. The newly applied DWR will rarely be as good as the original. And, if you apply a lot, the breathability of the fabric will suffer as a result.

Are DWRs harmful to the environment

Let’s put it this way: DWR treatments and the environment don’t really see eye to eye. The focal point of the discussion are PFCs, which, simply put, remain in organisms for years and don’t degrade in the environment. Traces of PFC can be found in the remotest corners of the earth. For a long time, we had been under the assumption that there were no direct health risks associated with these compounds and that “only” producing, washing and disposing of outdoor products were the problems. Hmm. But, a growing number of studies on both humans and animals have suggested that there are indeed health risks associated with PFC, with adverse effects on vital areas of the human body, such as the immune system, hormonal balance and reproduction.

Just how significant these risks are has been a topic of heated debates. There has been a lot of speculation as to where which PFCs accumulate and to what degree and as to which degrade and how quickly they do so. For this reason, C6 PFC based fluorocarbon water repellents were deemed safe, while C8 DWRs were not. However, critics, such as the founder of Nikwax Nick Brown called this a “fairy tale”. Brown believes that only the complete elimination of PFCs could really reduce the health and environmental risks.

Frequently water repellen coatings are generated by chemical substances that can harm your health.

Protection from rain without any risk to your health or the environment will put a smile on anyone’s face – even in the rain!

Due to Brown’s convictions, Nikwax became the first company to refuse to use PFCs and has continued to do so to this very day. Because scientific research has repeatedly demonstrated that all PFC compounds really are harmful to our health and the environment, more and more manufacturers are beginning to follow suit. In addition to Nikwax, Toko also offers PFC-free care and proofing products, but do so more to accommodate the increased interests of their customers than because of pressure from lawmakers.

It had been long regarded as “technically impossible to produce an equally efficient DWR without PFCs“, that is, a treatment that not only repels water but dirt as well, thereby maintaining the breathability of the fabric. PU or silicone treatments may be environmentally friendlier, but they pale in comparison to PFC when it comes to functionality.

But, as the pioneer in all things sustainability, Vaude, states in their 2016 sustainability report: “Thanks to today’s innovative technologies, this is now no longer a problem.“ The only “drawback” to PFC-free DWR treatments is that they’re not oil-repellent, but Vaude claims that this is not really necessary. And, it’s kinda true. Think about it: how often do you have problems with oil being on your functional clothing in the forest or up in the mountains? Probably pretty rarely.

Like in so many other areas, Vaude is paving the way with its DWR Eco-Finish. There are several more fully functional environmentally friendly alternatives currently in research and development, so hopefully there will be a few others that reach market maturity at some point.

Whilst Vaude plans to manufacture its entire collection completely PFC-free by 2020, other manufacturers already have one or more PFC-free collections. A real milestone could soon be achieved by Gore-Tex, whose materials are known to be used as precursors in many garments from numerous outdoor brands. Gore-Tex has announced that they will eliminate PFCs by the end of 2023.

Until then, you can turn to the following PFC-free and environmentally friendly alternatives:

  • Bionic-Finish Eco is based on hyper-branched hydrophobic polymers, which significantly improve the water and dirt-repellent effect and are even highly wear-resistant and hold up when washed as well. Plus, a Bionic Finish Eco will not ruin the breathability of a fabric. Eco Finish is Vaude’s DWR finish made of biodegradable substances.
  • Ceplex and Dermizax can be regarded as alternatives to DWR treatments as well but work in a different way. Ceplex is a PU coating, and Dermizax is a kind of PU membrane with moving molecules.

Water repellents are an extremely important part of your arsenal against wet weather. So, if you don’t want to walk around soaking wet, you better make sure you have one and keep it in tip-top shape! But, don’t use any old thing – be sure to go environmentally friendly! Your health and the environment will thank you for it!

Comments on this post

  1. Mikael said on 13. March 2019 at 16:07

    Hi, thank you for the great article. One question, do we know what e.g. Vaude uses? In chemical point of view I mean. Some information should be available shouldn’t? Not saying that this is the case but in industry there have been many incidents during years and decades than when something is banned and new substitute enters the market then after some period there is finding that new substitute was sometimes worse than original one or just subtly better. And round starts once again. Luckily EU REACH is state of the art for civilization and we are spoiled to have far safer products but of course that regulation is not that speedy. So do we know CAS numbers for new alternatives or are those trade secrets as way too many times?

  2. Expert Marco said on 29. March 2019 at 08:31

    Hello Mikael,

    unfortunately even Vaude doesn´t provide detailed information about the cemicals they use in the DWR coatings. The only thing they promise is, that every garment they produce will be completety PFC-free until 2020, thanks to their ECO-finish.

    Kind regards,

    Marco

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