Durable Water Repellent (DWR)
The first line of defense for rainwear is not a laminate or coating but the durable water repellent (DWR) applied to the fabric's outer surface.
All waterproof/breathable garments are treated with a DWR finish (as are most water-resistant soft shells). DWRs do not inhibit breathability because they do not coat the textile surface; instead they bond to the textile's fibers and do not fill in the interstitial spaces between those fibers.
The purpose of DWR finish: Allow a garment's face fabric to shed water, prevent saturation and keep water from sitting atop a WP/BR membrane. Garments remain light when they avoid becoming waterlogged.
Randy Verniers, a technology specialist at Marmot, explains that DWRs work by increasing the "contact angle" or "surface tension" created when water contacts a textile. An optimized DWR forms a chemical chain of microscopic, tightly packed vertical "spikes" on the outermost fringe of a garment's exterior. This dense, spiky buffer leaves no room for water to spread out, forcing it to form in round droplets. As such it beads up and swiftly slides off the fabric, having no opportunity to flatten out and seep into the textile.
Fluorocarbons (sometimes called fluoropolymers) can create the steepest angle and are the most common DWRs. Silicone and hydrocarbons are also used. Non-chemical DWRs are being studied, though none offers the performance standards achieved by chemical DWRs.
DWRs are at their best when new, but their performance can diminish with use. Their molecular chain, says Verniers, is masked by dirt and oils and can also be affected by abrasion. Such things reduce the surface tension and allow water droplets to flatten, spread out and penetrate the textile.
Regular laundering and a brief spin a clothes dryer (about 10 to 15 minutes at medium heat) can revive a DWR. After prolonged or rugged use, though, rainwear will likely need to have its DWR reapplied. Spray-on and wash-in reapplication products from companies such as Granger's, Nikwax, ReviveX or Sport-Wash accomplish this goal. Verniers prefers spray-on products, since wash-in products may impact a garment's breathability.
Additional details on maintaining and reviving a DWR is explained in a separate article, Rainwear: DWR Care.
- Read and follow care instructions included with your garment, usually printed on a tag and stitched into a seam. Manufacturer instructions supersede any tips offered here.
- Rainwear manufacturers usually encourage people to wash their garments regularly. A clean rain jacket outperforms a dirty or smoky garment.
- Despite the expense, specialized cleaning products created specifically for WP/BR rainwear are often recommended by manufacturers. The key reason: They rinse away cleanly. Mass-market detergents include additives (optical brighteners, foaming agents and more) that leave behind surfactant residues that can impact performance. Specialized products are available from Granger's, Nikwax, ReviveX or Sport-Wash.
- If a grocery-store detergent is your only choice, select a variety labeled "free" or "clear." Typically they include fewer additives.
- Whatever cleaning product is used, always rinse thoroughly; 2 rinses cycles are usually advised to remove all soap reside.
- Hand-washing or front-loading washers are preferred; top-loaders can potentially snag a garment on its agitator.
- Close any zippers, empty pockets and fasten any rip-and-stick (aka hook-and-loop) closures to prevent possible abrasion while garments tumble. Turn garments inside-out.
- Prewash stain removers such as Shout and Spray 'n' Wash are usually acceptable. Check instructions for your particular product.
- Things to avoid (unless otherwise specified):
- Fabric softener and dryer sheets. They contain waxes, oils and fragrances that diminish WP/BR performance in fabrics.
- Chlorine bleach.
- Dry cleaning.
- Open flames or intense heat (synthetic WP/BR materials can melt).
- Rain jacket or rain pants may not last a lifetime. Some reasons why:
- Hard use can cause snags, rips and tears on the face fabric; this makes a garment vulnerable to leakage.
- Even if the face fabric does not rip, a hard fall on rock or ice can cause a shearing effect on laminate or coating, which can permit leakage.
- Basic DWR revival and reapplication advice was mentioned earlier in this article. For a more detailed explanation of durable water repellents, please refer to our companion article,Rainwear: DWR Care.
- We offer more elaborate fabric care advice in another article,Cleaning Technical Fabrics.
Rainwear: Durable Water Repellent (DWR) Care
When Do DWRs Need Maintenance?
Test your rainwear by sprinkling or spraying some drops on its exterior. Does it bead up and roll off? Your DWR is in good shape. If you give the fabric a single strong shake, does most of the moisture fly off? Ditto.
If, however, the water sits on the fabric and that section begins to darken slightly, water is making its way to the fibers and wetting the fabric. This indicates your rainwear needs attention.
The performance of DWRs can be diminished by:
- Dirt and body oils:Fix it by laundering the item, then giving it a 10- to 15-minute spin in a clothes dryer at medium heat.
- Multiple laundering:Keeping a rainwear item (and its DWR) clean is universally recommended, but after dozen or two washings, a frequently laundered DWR may need revival. If not badly soiled, all a garment may need is a short spin in a clothes dryer at medium heat. Yet if the fabric continues to show blotches of wetness, the next fix is to reapply a DWR with a spray-in or wash-in product.
- Abrasion:Lab tests at REI have shown DWRs can withstand a lot of abuse, but constant abrasion against rocks can scrape away the finish. This is fixable by reapplying a DWR with a spray-in or wash-in product. (Some textiles pros tell us they favor spray-on products; wash-in products may impact linings.) Contact with a pack's hipbelt and shoulder straps will not likely wear away a DWR, but such rubbing can diminish performance by breaking down the surface tension water when it contacts the fabric (as explained in the next section). A 10-minute spin in a dryer (medium heat) may be all that's needed to improve performance.
How to Revive DWRs
First step: Cleaning. Follow the cleaning instructions described above for the type of rainwear you own. Washing away dirt and oils does much to restore a DWR's water-shedding abilities.
Next step: Apply heat. After washing, exposure to heat does the most to bring a DWR back to life. Generally speaking, you should place the garment in a dryer set for medium heat for up to 15 minutes.
Some Subjective Observations
Other factors beyond rainwear's WP/BR technology should influence a purchasing decision: Weight; packability; appropriateness of the face fabric (Burly for bushwhacking? Wispy for high-speed ultralight travel?) for your primary activity. These and other considerations are discussed in our companion article How to Choose Rainwear.
Other factors beyond rainwear's WP/BR technology will impact wearer comfort: Lots of good, breathable rainwear choices exist, and some (particularly 3-layer laminates) tend to consistently outperform others in breathability. But even their performance expectations can be overwhelmed by overly aggressive use. A key objective when wearing rainwear during exertion is to avoid moisture build-up inside the garment. The best defence: Be alert and actively manage your comfort level.
- Personal metabolism:If you heat up easily, modify the pace of your activity.
- Exertion level:Same principle; slow down or speed up as needed.
- Weather conditions:If it's warm and steamy out, no rainwear feels comfortable; if it's cool and dry, keep a light insulating layer handy for rest stops; in other words, be alert and nimble; adapt as conditions dictate.
- Clothing worn underneath:Shed a layer if you're uncomfortably warm.
- Use of vents:If you rainwear has underarm zips, core vents, use them (in addition to your main front zip) to speed sweat's evaporation.
Polyurethane and polyester laminates: Beyond eVent, PU and, to a lesser extent, polyester laminates are also challenging the dominance of Gore-Tex. The bi-component Gore-Tex membrane includes an anti-contaminant polyurethane layer but for years has outpaced PU competitors because its PU layer was the thinnest around (due to the structural support provided by its ePTFE layer). Yet newer PU membranes claim to offer comparable performance.
Coatings: Casual explorers, weight-conscious travelers or budget-minded shoppers are usually quite happy with lower-cost WP/BR coated rainwear. Just be aware that if you are in one of those groups and you evolve into a high-energy adventurer, most likely you will want to upgrade to a higher-performing WP/BR technology.
Maintenance: Clean your rainwear regularly to keep it performing at its best. If you notice wet blotches on the face of a rain jacket, you need to revive its DWR.
The future: Textile technology is a fascinating field. Ideas and innovations are being hatched all the time. Accept the fact that today's whiz-bang technology may become tomorrow's dinosaur.