Hydrolysis is the ageing process that occurs in all footwear with a cushioned PU mid-sole, independent of the manufacturer.

Hydrolysis is the ageing process that occurs in all footwear with a cushioned PU mid-sole, independent of the manufacturer.

For years, fly fishermen have encountered delamination issues with wading boots and blamed it on the quality of the boots. Yes, there are many brands of wading boots that are of inferior quality. But there are also wading boots of the highest quality (like Simms wading boots) that experience what many anglers perceive to be quality issues. When in fact, the boots are going through a process known in the footwear industry as hydrolysis. So what exactly is hydrolysis?

The Process of Hydrolysis

Hydrolysis is a normal material aging process that occurs in all footwear with a cushioned PU midsole. This process is independent of the manufacturer. It also occurs in motor vehicles, tyres, ski boots or helmets. It does not represent lower quality or even a quality issue in materials or workmanship. Hydrolysis is an ageing process which occurs over a number of years but which can be accelerated by certain factors. Damp conditions are specific catalysts for hydrolysis as they increase the amount of contact the PU has with water molecules. Hydrolysis is therefor more likely to occur in boots which are worn in wet conditions without being cleaned afterwards.

Even if wading boots are cleaned after use, the effects of hydrolysis will at some point in time effect the glues used during the manufacturing of the boots. However, one of the most common factors accelerating hydrolysis in wading boots is actually lack of use. By leaving your wading boots at the back of a dark cupboard or in your garage for too long without using them, you’re increasing their exposure to moisture absorption and consequently hydrolysis.

The Invisible Culprit

When you witness the ‘sole-destroying’ moment the soles of your wading boots start to fall apart, your first thought might be to blame the manufacturer. You might question if you have a faulty pair, particularly if the boots have only been worn a few times. Unfortunately, this scenario is far more common than you might think and hydrolysis is the invisible culprit to blame. Whilst your wading boots are in the cupboard or garage, hydrolysis is likely to be hard at work. As the PU in the wading boots is exposed to increasing amounts of moisture over time, it becomes more porous allowing hydrolysis to get to work at destroying the PU in the soles. As the process of hydrolysis is invisible it is only when you notice the sole disintegrating and falling off the boot upper that you can physically see its effects.

Storage and Care

As durable as your wading boots are manufactured to be, it is crucial that they are cared for in the correct way to ensure this level of quality is maintained. To prevent the effects of hydrolysis there is a shoebox of tricks on how to store and care for your wading boots. In order to successfully combat the damaging effects of hydrolysis we recommend that you keep your wading boots clean and cool by doing the following:

  • Store your wading boots in a dry and well-ventilated space
  • Keep your wading boots away from sources of heat and avoid exposing them to high temperatures
  • Clean your wading boots after a fishing trip


Providing the correct storage and care for your wading boots is crucial to ensuring they live a long and happy life. However, the wisest piece of advice which we can really give to keep your wading boots healthy is to get outdoors and fish more regularly. Before longer trips take your wading boots on a short test run to check for signs of hydrolysis. This is particularly important if you know your boots have been hidden at the back of the cupboard or in the garage for a while.

It’s crucial to remember that wading boots are designed to be worn in outdoor terrain and so the easiest way to prevent hydrolysis is to keep your boots moving in the open air and in the water. This way hydrolysis doesn’t have the right conditions to wreak its usual havoc, allowing the soles of your wading boots to remain intact. Whether it’s a day out on the Vaal or your nearest mountain stream, or a month long trip to New Zealand, any regular fishing trip will be doing your wading boots a massive favour.