Reproofing your waterproof

Why do you need to keep fabrics/ membranes clean?

Essentially, technical fabrics work best when they are clean. Dirt and contaminants (which could be mud, sweat, body oils, insect repellent, food or even detergent residue) reduce the ability of a fabric to repel water or transport moisture. Regular detergents often have additives including surfactants that attract water (to help loosen dirt), which work in exact opposition to DWR if not rinsed thoroughly. Washing with pure soap or a specialist cleaner e.g. Nikwax Tech Wash will avoid this issue. Just remember never to use fabric softeners or conditioners on your technical clothing, as this will destroy any wicking, repellency and breathability it once had!

What does a re-proofer do at a chemical/microscopic level?

At a microscopic level, the chain-like molecules of the DWR treatment bind to the surface of the fabric and act like a fringe of spikes which makes water bead up and roll off the surface. When these spikes or fronds get abraded or contaminated their orientation gets disrupted and that is what stops them from working. The DWR treatment applied to the face fabric during manufacture won’t last forever, and will become less effective over time. Abrasion (from pack straps or even just the fabric rubbing against itself) and dirt inhibits the action of the DWR. If your garment stops beading up it doesn’t necessarily mean the DWR has worn off; it may just have been masked temporarily and can be revived. Often just washing and then applying heat either by cool ironing (which can be done over a tea towel if you are nervous about the fabric) or tumble drying on low will help realign the molecules, and make the fabric bead up again.

If after washing and heat treating your garment the DWR is still not working, then it’s time to re-proof. This is effectively topping up the factory applied DWR with an off the shelf re-proofer product such as Nikwax TX Direct. The re-proofer works partly by binding to the existing DWR molecules, so it’s best not to wait until the whole of the garment is wetting out straight away; re-proof when key areas like the cuffs, sleeves and shoulders stop beading and you’ll get better results. Spray on re-proofers are best for waterproof shells as they allow you to target problem areas, and treat only the outer surface of the fabric (which is what you want), whereas wash-in re-proofers are better for insulated or down garments as they will treat the whole garment. The key is to re-proof when the garment is clean, and to use heat to reactivate any remaining C6 DWR.

Why do we have to apply heat after treatment?

The factory applied DWR used on current Alpkit products uses C6 technology, which is re-activated by heat. Depending what re-proofer you use, the manufacture may state that it does not need heat curing to be effective; however we would say that it won’t do any harm to the re-proofer by heat treating it as well, and it will help revive any remaining C6 DWR on your garment. You can use a tumble dry on low setting, but bear in mind the mechanical action of a tumble dryer will cause wear and tear to the whole garment each time you do it. Tumble drying is the best option for insulated and down jackets, as it will help dry out the insulation at the same time. For waterproof shells then a cool iron allows you to be more precise with your heat application and limits the mechanical wear and tear. If you are concerned about the fabric you can always place a tea towel between the face of your garment and the iron.

How often do you need to re-proof?

This very much depends on how much you are using your gear. The simplest advice is: wash it when it is dirty (and at least 6 monthly) and  re-proof it when water starts failing to bead up. You don’t need to re-proof every time you wash, but if in doubt act sooner rather than later. If you don’t wash the garment soon enough and leave re-proofing until the whole garment is wetting out, you’ll have a hard time re-storing the DWR performance.

An environmental aside:

DWR treatments used to be made with C8 fluorocarbons (PFC), but evidence has shown that this can break down into PFOA and PFOS which can accumulate in the environment, with negative effects. Several years ago the outdoor industry moved away from using C8 in favour of C6, which does not breakdown into PFOA and PFOS. However, the down side of C6 DWR treatments is that stain resistance and durability are slightly reduced compared to C8. Neither is it perfect from an environmental point of view. There are PFC-free DWR treatments available (‘C0’), but they often have zero stain resistance and even less durability. Why does stain resistance matter? Because dirt and oils (including those from your own body) inhibit the action of DWR. It seems there is a conflict between more environmentally friendly DWR formulations and performance level; the reality is that DWR performance has been reduced in recent years, and may continue to be until some clever scientists (of which many are working on this precise problem) come up with something better.