Rain jackets aren’t as ‘waterproof’ as they once were and why that’s a good thing

Posted by Trek and Travel Staff on

Written by Sean Janda, Translation by Jemima


Our resident gear geek and physics fanatic, Sean Janda, breaks down the DWR technology behind wet weather jackets. Jemima’s on hand to translate his findings.


We all know that a hard shell jacket is a must for any adventure. It keeps the rain off you, in tough conditions it will significantly reducing the risk of hypothermia and at the very least it will improve your walk by keeping you dry and comfy. What’s less known is how the jacket keeps you dry. The best jackets will use multiple technologies to keep the rain out and almost all of them will have a DWR treatment on the outside.


The ability of a waterproof fabric to prevent the transport of liquid water through the membrane while allowing the transport of water vapour away from the wearer relies heavily on a durable water repellent (DWR) treatment. This DWR coating when applied to the outer layers of a garment causes water to ‘bead up’ and allow more surface area for water vapour to move through.


This means that when you’ve bought your new rain jacket you’ll find that the coating (DWR) on the outside makes the water bead and run off the jacket rather than soaking into the fabric.


After a while however the coating will rub off through normal use and regular washing. This will cause the water to adhere to the outer surface as well as to itself by surface tension and breathability will be reduced.


Basically this means that when you wear it and use it (which you should be doing) the DWR treatment will rub off eventually. When your jacket loses its DWR and the water looks like its soaking in to the fabric rather than beading off it isn’t going to be as breathable so you’re going to feel colder and damper.


In the past manufacturers used the most common type of DWR treatment which is a fluoropolymer chemical called perfluorooctanoic acid (aka C8). C8 was great because it stuck well to fabric, it took many years and a lot of abrasion for the DWR to come off. Manufacturers were quick to get rid of C8 as a DWR because it was discovered that the chemical was carcinogenic, a selective reproductive or developmental toxicant, and disruptive to endocrine activity. C8 is known to cause all the previously mentioned health issues in very low concentrations (mere parts per billion) and persists in soil and drinking water.


So far there aren’t many fabrics that keep the DWR on forever. The older jackets had C8 DWR which performed better but wasn’t great for the environment or the people making the garments.


Pros of C8 – DWR treatment lasted longer so the consumer didn’t need to reproof as often

Cons of C8 – Not good for the environment or for the workers putting the garment together.


When manufactures learned about the negative impacts and effects of C8 they were quick to replace it with an alternative perfluorohexanoic acid (aka C6) which was found not to be carcinogenic, not a selective reproductive or developmental toxicant nor was it found to have the same hormonal negative effects that C8 had.

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This new alternative C6 was certainly not as bad as C8 however it doesn’t have the durability that C8 had. This means that you’ll find that your newer hard shell jackets will ‘wet out’, aka lose that water beading quality, faster than jackets you may have had in the past.


Basically this means – the old system of DWR or C8 was better at keeping the water beading for longer but wasn’t good for the people applying it or the environment. The new system of DWR or C6 doesn’t have the negative qualities at C8 had but it doesn’t keep your jacket feeling as waterproof for as long.


FEAR NOT! Buying a wet weather jacket that loses its beading more frequently isn’t the end the world there is an easy remedy. Just like you have to grease the chains on your push bike or check the oil in your car, you just have to tend to your jacket more often. Give it a good wash and reproof every few months to ensure that gorgeous beading keeps water running off you on all your adventures. Hard shell jackets are just like everything you own, show it some love and care and it will love and care for you back.

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