Shoe in water

Chemicals and Footwear: Just a whole heap of toxic stuff?

Synthetic chemistry has allowed footwear to perform better, but now that knowledge around the impact of the chemicals has grown – the whole subject area needs revisiting. It is NOT bad news: two outstanding schools of thought have demonstrated that with proper management there can be both performance and compliance to better practice before the regulations kick in. The two easy answers: the first was exampled by the Lowa boot at last Performance Days that had every component pass Oeko-tex; the second is to turn to better leather (namely Leather from Regenerative Agriculture – which will be planet beneficial in terms of carbon accounting, but be aware there is also RegenAG rubber, wool, cotton and bast fibres on the market too). The leather industry should be congratulated for formulating better tanning processes which have allowed the dropping of the dangerous and toxic chemicals. Just like with apparel textiles the finishing of fabrics comes under scrutiny – of which the water repellent finishes need addressing too.

The textile industry has moved away from Fluorine chemistry; this has affected the lighter weight fabric footwear twice over as PFAS was used in both the Durable Water Resistant finish, but it is also an Ingredient in the manufacturing process of microporous membranes. M/P membranes are those associated with the biggest Ingredient brand: Gore-tex; the good news is that the permeable waterproof membrane manufacturer has been able to swap to a different substrate that does not involve PFCs in its construction process; plus, the PFC-free DWRs are now the industry standard. Both of these swaps have happened before legislation comes in around SVHC/ RSLs/ REACH. Do not get depressed - the science of a material that is both waterproof and allows perspiration to escape is leading edge: every potential solution is a compromise. If there was a magical answer that solved this every brand would use it, perhaps the problem is the over-marketing of what is offered...

The swap over of membrane materials has also brought waterproof membranes into focus again. Essentially there are 3 mains types of membranes: microporous, hydrophilic, and electrospun – they all have their pros and cons. If you want the best permeability then electrospun is the solution, but the new PFC-free version is still in need of extended trial feedback – its downside: the hydrostatic head readings wear fastest so it will be the first membrane to get near the 1000mm waterproof level. In my opinion – a very good soft-shell solution, but yet to be proven for hardcore wet weather.

Microporous will give some of the best initial readings balancing between waterproofness and breathability; however the effect of the DWR needs returning to.

Hydrophilic is the third option – its Laboratory permeability readings do not seem the best, but they work (just not as well as the other two!).

The start point is footwear is worn for extended periods, plus DWRs are not perfect. The new generation of the water resistant finish have problems with adhesion to the fabrics, plus they can be over whelmed. In simple terms a cheap DWR can suffer from being wetted-out within half an hour; the best will be compromised within four hours. There are other factors than also help contaminate DWRs (like the detritus from perspiration, grass and mud, plus the physical wear-off from usage). To solve the latter, look out for solutions that pass the Bundesmann testing protocol.

The solution: perhaps revise the membrane technology. A wetted out micro-porous system can lose 50% of the permeability rate, whilst a hydrophilic system will only go down around 20% - which means that under extended conditions a hydrophilic system will produce the best breathability rate.

Whether this is flagging up a weakness in Laboratory testing or just the flaw of not being able to repeat real life conditions is not the point of this blog – nothing is perfect, but perhaps the concentration on DWRs in footwear has not been as open a view as it could have been. A compromised DWR does NOT make the membrane leak (the waterproof layer is still there; it just does not breath as well as the Lab test results hint).

Of course, there is a better solution: to use a well-conditioned leather will champion the results. Nature always has better solutions than most appreciate. In a perfect world use a one-piece construction (this minimises seams – areas that need to be taped to remain waterproof, but by the very nature of being taped the area is a zone that is more probable to wear out as well as not being as permeable as the material itself).

As with all things performance footwear related – the primary reason for buying the product is comfort in action alongside the aesthetic – unlike AthLeisure/ Gorpcore/ Sport Fashion, the appearance is not the main consideration, but it does have the influence to cancel a purchase if the item looks duff. Factors like price, material claims, plus the CSR factors associated with the brand come next.

However, if you want to have the product with the least environmental impact there is a simple solution: build the best product that lasts for the longest time (so the bits that wear out like soles can be repaired). The core focus of the Circular Economy is to enable the original shoe to keep going as long as possible…

Charles Ross

About the Author

Charles Ross

Royal College of Art- Lecturer in Performance Sportswear Design

Having exchanged being an Outward Bound Instructor for the warmth of indoors, Charles has helped teach the next generation of designers for two decades now. Sustainable through longevity is a core principle.

Go back

Exhibitor List March 2024