DWR (Durable Water Repellent) Coatings, Ratings & Applications

When you’re shopping for outdoor gear, particularly camping and backpacking gear, it’s likely that “waterproof” is pretty high up on the list of qualities you’re after. Few things are less fun than a leaky tent… except maybe a backpack full of drenched supplies, or a rain jacket that doesn’t protect you from the rain. Today, we’re going to talk about some of the technology that keeps you dry even in the rainiest weather: durable water repellent (DWR).

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What is DWR? | How Do They Work? | DWR Ratings | Rejuvenation & Reapplying

 

What Is Durable Water Repellent (DWR)?

Durable Water Repellent (DWR) is a chemical application that manufacturers use to create rain-proof gear, like rain jackets, rain pants, and waterproof backpacks. DWRs make water bead up, then disperse, preventing surface moisture from accumulating on rainwear. Even in a waterproof jacket, it is important that the surface doesn’t just keep water out, but pushes water away. If you have a soggy surface, your skin feels clammy and wet, even if the water does not actually penetrate the surface.

Though the technology might sound very modern, it might be said that the first DWR was the oils that our hunter-gatherer ancestors worked into animal hides thousands of years ago to improve their durability. There is a long history of working a chemical compound into textiles to increase water resistance. Oilcloth, used by sailors, fishers, and whalers of old, used linseed or other oils to create a cloth surface that allowed water to roll right off. Animal fat rubbed into leather used by the Indigenous people of North and Central America did the same thing. What makes modern DWRs different is that the application is much longer-lasting and less labor-intensive.

The first modern DWRs were sold in 1969, shortly after the introduction of Gore-Tex. It was noted that if the outer layer had an exterior coating that could repel water, the whole garment would perform significantly better. Today, Gore-Tex still uses DWRs, as do many other businesses selling weatherproof products.

 

How Do DWRs Work?

While we’ve talked about waterproof ratings before, DWRs work a little differently than other types of waterproofing. DWRs are applied to fabric by chemical vapor deposition, dipping, or spraying at the factory. The application changes the surface texture of the fabric and allows water to collect in droplets or beads, that then roll away. If you’ve ever heard the phrase “like water off a duck’s back,” it’s the exact same concept. The combination of chemistry and physics produces a surface that water just can’t stick to, and it rolls away, keeping you dry.

It is important to remember that DWR improves water resistance and rain-proofing, but is only part of the waterproofing equation. For light rain exposure, fabric treated with DWR is fine on its own. For heavier weather conditions, you will want a multi-layer waterproof fabric to help keep you dry. DWR is an exterior coating, and when combined with multi-layer interior membranes, it helps create high-performance weather-resistant gear.

 

How Long Do DWRs Last?

Because DWRs are a surface treatment, they don’t last forever. If you don’t wash your gear, oil and dirt buildup can change the surface texture that lets water roll away. On the flip side, if you wash your gear with harsh detergents, that action can strip off the waterproof coating.

Abrasion can also rub off the DWR, so if you find yourself sliding down a hill, you might find that you need to give your jacket a refresh when you get home. But even if you don’t put that much wear and tear on your jacket, “hot spots” where there’s a lot of contact with your body or a lot of folding and movement can crop up and let water in. Your jacket’s shoulders are also going to lose DWR effectiveness quickly, thanks to the rubbing from your backpack’s straps.

There is no one formula to figure out exactly how long your DWR will last, but fortunately, there is an easy way to test your gear’s DWR capacity. We’ll go over that in a little bit.

 

DWR Ratings Explained

DWR ratings have two components. These numbers reflect how effective the treatment is and how durable the treatment is. When manufacturers test and rate their DWR-treated fabric, they spray water on it and look at how it performs.

The first number is a score out of 90. This shows that approximately 90% of the fabric has no water sticking to it after being sprayed because the water has beaded up and is ready to roll off when the fabric moves. The higher the number, the better the rating. For anything you’ll be wearing, like a jacket, you don’t want this number to be under 80. If you buy a jacket with a rating of 75, that means that 25% of the water is going to be left on the fabric and that often means that it’s going to spread out and soak into the fabric rather than roll-off.

The next step is to wash the fabric several times before repeating the test. Usually, the washes are repeated in groups of 10. You want this number to be as high as possible, too, because when taken together, the two numbers mean that the DWR maintains its original durability after that number of washes.

Of the two numbers, the first is more critical. You can extend the life of your DWR by rejuvenating or reapplying it, but if the first number is low, then the resistance isn’t that good, to begin with. In recent years, the wash durability number has trended downward. This is because DWRs have changed a lot in the past few years for environmental reasons. We’ll talk about that more later, and why it’s important to keep that in mind as you’re shopping.

Not all manufacturers publish their DWR ratings. That doesn’t necessarily mean they have something to hide, but if you see a rating, here are some guidelines for interpretation.

 

Why Use DWRs?

Whether you are surprised by showers or plan on hiking in a little light rain, being prepared for wet weather conditions can keep your hike fun and safe. Choosing fabrics that have been treated with DWRs is a great way to do that. If you don’t want to go out and buy new gear, you can also DIY DWR- if you have a favorite pair of hiking pants or other gear that wasn’t designed to be rain resistant, you can apply an at-home DWR coating to give yourself a little extra protection.

Speaking of protection, tents and sleeping bags are often coated with DWR. Not just to protect you from the rain, but to keep you dry when morning condensation forms. This is critical in cool weather, where unexpected wetness can bring your temperature down dangerously. DWRs are great for this because they’re so lightweight that they don’t really add anything to your load.

 

Pros of DWRs

• DWRs are lightweight and don’t do much to change the surface texture of your gear– they don’t feel “crunchy” like some protective sprays can
• DWRs keep long-term gear costs down. If your DWR-treated rainproof jacket starts letting water through, you can rejuvenate it or even retreat it!
• DWRs repel water, meaning that your skin won’t feel clammy due to a saturated outer layer

 

Cons of DWRs

• Some DWRs are toxic to the environment

There is one big problem with DWRs: most of them are not environmentally friendly. The chemical used in virtually all DWR predating 2010-2015 is a long-chain fluorocarbon-based treatment. This is an extraordinarily durable, highly effective treatment with toxic byproducts that persist in the environment. These byproducts are dangerous to humans, plants, and animals, and now many governments have banned the manufacture and use of these long-chain treatments, as well as their sale.

As hikers, fishers, and backpackers, we know just how important it is that we protect the environment. Leading outerwear manufacturers know this, too, and there is a lot of promising work on DWR solutions that are less toxic to the environment and people. While there are several potential solutions, none are quite as durable as the old long-chain fluorocarbons… yet. Science is still working on this one!

While many experimental DWR finishes, like silicone-based finishes, do have the same effect, they are not as durable and are easily contaminated by dirt and oils. The current leading solution is that companies have switched over to a shorter-chain fluorocarbon treatment with byproducts that break down faster. There’s lots of great research happening on DWR treatments that are durable and green. If you are looking for the greenest DWR, “PFOA-Free” is the term to look for when shopping.

 

Applications of DWRs

You can buy almost any gear with DWR coatings. Tents, backpacks, hats, pants, jackets, gaiters, the list goes on! If you can take it outside and it might get rained on, you can get a version of it that’s been treated with DWR.

If you’d like to try DWR coating for yourself, it’s important to remember that it prevents water from penetrating the fabric. This is great for outerwear, but not for innerwear. There’s a reason that nobody makes DWR-treated underwear! However, DWR will let you turn your favorite hat into a rain hat, and can improve the water-resistance of your comfiest windbreaker. You might also want to consider coating the family tent with it– it never hurts to be prepared for bad weather, especially if you’re camping with kids or in harsh environments.

 

How To Test Your Jacket’s DWR

If you want to test your jacket’s DWR, do what the manufacturers do. Get it wet! You can splash it with water, spray it with the hose, or use your kid’s Super Soaker to simulate a rain shower. Then, shake it off. If the water beads up and starts to roll off, and then if those beads fly off when you shake it, your DWR is good to go. If the water stays on or “wets out” (meaning that it soaks into the fabric, causing a wet spot), you need to first try rejuvenating your DWR. If that doesn’t work, it’s time to reapply.

 

How To Increase a Jacket’s Water Repellent Capabilities

There are two things you can do to increase your jacket’s water repellent capabilities regarding DWR: Rejuvenation and reapplication. Try them in that order, because many jackets just need their DWR reactivated, rather than fully reapplied.

It’s also good to remember that newer DWR coatings are more environmentally friendly, but this has come with a durability tradeoff. This just means that you will need to rejuvenate or reapply more regularly. The upside is that these new coatings are just as effective- remember those ratings we talked about? Even if the second number (the wash durability) is often lower than other coatings, the first number can be just as high. They’ll keep you dry, just like the older versions. You just need to take good care of them.

 

Rejuvenation

The first step in increasing your jacket’s water resistance is to clean it. Washing away dirt and oil can help restore DWR’s water-shedding abilities, but don’t just throw it in the washing machine without checking the care instructions! Those will be on the label or the manufacturer’s website. You should also use a technical fabric cleaner (like Nikwax’s Tech Wash) because they do not have additives that can interfere with the coating.

When you dry your jacket, be sure to use low or medium heat– and check before you put it in the dryer. Not all jackets can be machine-dried. You might need to put it on the line or just over the back of a chair somewhere until it dries.

After you wash it, you need to apply heat again. You need to do this every time you wash your DWR-treated gear. There are two ways to do this. First, once your jacket is dry, put it in the dryer for twenty minutes on medium heat to reactivate the finish. Only do this if it’s safe to do so, though!

If you can’t put it in the dryer, you can use an iron to revive the DWR. You need to set the iron to “no-steam” and have it on warm, not hot. Then, iron your jacket. Do not directly apply the iron to the jacket’s surface. Make sure you have a thin towel or cloth between it and the iron as you work. A clean bed sheet is perfect for this.

 

Reapplication

If rejuvenation didn’t work and water still soaks into your jacket, or if you want to add DWR to previously untreated fabric, this is how you do it. Even after rejuvenation, some jackets and gear will still need reapplication because DWR can be rubbed off, especially along the cuffs and collar. You can use either a spray-on or wash-in product, all of which are available in a variety of chemical types.

If you’re touching up a jacket or other article of clothing, we recommend spray-on DWRs. First, if you’re only reapplying to a small area, you will waste less product. Secondly, wash-in products can interfere with moisture wicking– so for garments that touch your skin (like pants), a spray-on is better.

However, if you’re reapplying DWR to something large, like a tent, then definitely go for the wash-in. This is more efficient and takes way less time! If you’re doing multiple articles of clothing at once, you might also want to use a wash-in product.

Most at-home DWR coatings are either short-chain fluorocarbon, silicone, or hydrocarbon coating. All have their pros and cons, but you do not have to use the same kind of DWR coating as the original on your jacket. You can use whichever coating you like best– they will not interfere with each other.

Every manufacturer will have instructions for reapplication. The process usually involves washing the gear with a special, additive-free technical wash first, and then simply applying the product as necessary. This could mean soaking the whole garment, or it could mean just spraying down the “bald spots.”

Finally, after you’ve reapplied, it’s good to apply more heat again using the dryer or the iron. That way older DWR gets touched up and reactivated, and entirely new coatings perform at their peak.

 

What We’ve Learned

• DWRs are great for keeping you dry, but you have to put in some maintenance to keep them working well
• DWRs are lighter than other waterproofing methods
• DWRs often work in tandem with other waterproofing methods like layering and membranes to keep you dry
• New DWRs have greatly improved the environmental side effects of old DWRs
• You can easily test your jacket or other rain gear’s DWR by spraying it with water and paying attention to what happens
• You can refresh DWR by washing, drying, and then applying heat from an iron

You can replace DWR with spray-on or wash-in products