Using preferred test methods

Why SATRA has ‘preferred test methods’ and how these can be used to produce the most realistic assessments of materials, components and whole footwear.

SATRA currently has over 270 published test methods that form the staple of footwear testing across the globe. Many are further interpreted and included in international standards. For nearly every method, associated performance guidelines have been developed. Both methods and guidelines are regularly revised in light of new innovation in shoemaking technology, new designs and new materials.

Occasionally, a completely new test method is developed for specific reasons through considered and diligent SATRA research responding to new requirements from members. There is, however, a subset of these – known within SATRA as ‘preferred methods’. Members that work particularly closely with SATRA will be aware that there are preferred methods that we recommend above all others.

What are they and why are they important?

There is wide variety of test methods across the globe. Some of these – but not all – measure the same property and persist in some footwear specifications. Specifically in this case, methods are used for the analysis of leather and textiles and other sheet or moulded materials, and the products made from them. However, shoemaking is very different from garments, upholstery and accessories such as bags.

Materials selection

The choice of materials for shoemaking is critical. Materials used in footwear must endure completely different conditions and requirements to those used for the aforementioned garments, upholstery and fashionable bags. The upper components will be cut with knives, are irregular and must not fray at the edges. They also need to hold stitching in every direction firmly and need to be durable.

Footwear is often damp, from the environment and from perspiration. This weakens the materials and, of course, the resulting product is in contact with the ground, so is subjected to walking or running forces and abrasion. Above all, they need to be formable into a three-dimensional (3D) shape, hold that shape to maintain their fitting and comfort, even while being flexed – possibly for many years – and not fall apart.

The shoemaking process is also quite harsh for a product that is essentially made of limp materials sewn (or closed) together and formed. Temperatures – in some cases up to 150°C – as well as extreme pressure and strain are common in shoemaking processes. Thus, the materials need to perform functionally, as well as being immune to this physical abuse. The grain, the surface, and even the aesthetics, will have to deal with quite harsh processes long before it reaches the retail phase and the wearer.

Some styles such – such as welted footwear – may be restitched many times as they are repaired, restored and resoled to extend their life, in order to preserve a favourite pair of shoes, or simply to extend its life for sustainability.

With regards to innovation, it is worth considering the growing innovation of including electronic components in footwear. Of course, electronic components are often tested intensively, so what about when their application is footwear? This introduces the special circumstances that footwear delivers.

Moisture is almost always present in variable amounts, whether from perspiration (which is corrosive) or simply from the environment, through rain and puddles. In fact, even rain contains small abrasive particles washed from the atmosphere as it falls.

Normal gait is not simply vertical load. Walking is locomotion, which also requires a horizontal force to create a sheer force, normally on the soling. When turning, there is a torsional force unless this is not attenuated by the sole unit (for example is the ground is slippery). These forces are transmitted through the upper. The foot will be contained by the upper and apply increased pressure on the upper sideways. This is the nature of footwear and often a surprise to innovators.

Testing specific to footwear

Accordingly, then, materials used in footwear should be tested in the context of their use specifically for this product – the demands made by the manufacturing processes and during wear. SATRA has spent over 106 years specialising in producing test methods that are specific and applicable to footwear. This article will delve into and highlight just a few examples of such specific preferred tests.

Water vapour permeability and absorption

SATRA TM47:2019 – ‘Water vapour permeability and absorption’ (figure 1) acts as a very good initial example of why SATRA has preferred test methods for footwear applications. SATRA TM47 is one of a vast array of tests available to assess breathability and therefore their selection of materials for use in footwear.

Many of the tests available around the world will give conflicting results, and in some cases even rank materials in a different order. This is as a result of the difference in the test methods between the temperature used inside and outside the shoe, as well as variations in humidity inside and out (these differences are called ‘gradients’). There needs to be a gradient, as that is what drives the permeability (commonly referred to as the ‘breathability’).

Permeability tests mostly rely on a passive physical concept that vapours (in this case the gas phase of water), strive to reach a dynamic equilibrium in the environment. This comes down to the energy of the water vapour molecules (temperature) and the absolute humidity of adjacent environments.

Therefore, at a higher temperature, and a higher humidity in a certain location on a shoe, the water vapour will travel and equalise with an adjacent environment. If the test is designed to measure water vapour permeability, it must be ensured that the test itself replicates the conditions present in the intended application.

In the vast majority of instances with regards to footwear, the internal microclimate will be warmer and more humid than the environment in which the footwear is being worn. Even if the outside temperature is warmer than inside the footwear, the likelihood of the humidity usually being overwhelmingly lower outside the upper is high, thus creating a gradient favourable to breathability. There are exceptions which are discussed later.

SATRA TM47 is specifically designed to recreate the conditions present in the majority of footwear items. This is 32°C and saturated underneath the material, with a standard controlled ambient of 23°C/50 per cent relative humidity (RH) above the sample, the ambient air being circulated to prevent a build-up of humidified air above the sample.

The sample can consist of a single layer of upper or lining, or a combination which may be laminated and include a membrane. Below this composite is normally a layer of hose – the sock. Each layer should be weighed before and after the test to assess the actual mass absorption of moisture. This has the objective of determining whether short-term or long-term comfort is afforded. If the hose has low mass gain following the test, this is indicative that the base layer against the skin is being kept dry and thereby comfortable.

As already mentioned, there are exceptions to the rule. Climates exist where the outside ambient conditions are warmer and more humid than inside the footwear, and innovative materials have been developed to deal with this scenario. In this case, SATRA TM47 is called upon with some special modifications.

SATRA’s innovation team produced a special machine. The standard SATRA STM 175 permeability and absorption test machine was modified with an active system so that the water bath could be either heated or cooled. In this way, the water bath could be placed in a climate chamber with ambient temperatures of 45°C and yet still hold its temperature to 32°C. SATRA TM47 has been used to measure the breathability of advanced active materials in environmental conditions that exceed normal in-shoe environments.

Incidentally, the predecessor of SATRA TM47 was used as part of the selection process of candidate materials for the footwear that was worn during the first recorded successful accent of Mount Everest in 1953. Therefore, there is quite some heritage attached to this test method.

Upper flexing

The previous example is somewhat critical of the conditions used in some other breathability tests. In the following examples, there are alternative SATRA methods discussed as they linger throughout the industry in various specifications. The purpose of the following information is to explain why there are preferred alternatives that may be suggested by our experts.

Essentially, there are two types of flex tests: i) to examine damage to leather grain and finishes on textiles, and ii) to examine the water resistance of materials.

For material damage as a result of flexing, there are two main tests. These are SATRA TM25:2020 – ‘Vamp flex test’ (shown in figure 2) and SATRA TM55:1999 – ‘Flexing resistance of upper materials – Bally flexometer’. While SATRA TM55 has persisted in specifications and standards, SATRA TM25 is recommended. Why is this?

Footwear flexes in a very unique way, as it is a unique product. This occurs in the vamp region when during walking and is quite different from the flexing conditions that SATRA TM55 reproduces.

SATRA TM25 is specifically designed to recreate a vamp flex event around the joint region of the footwear, over and over again. This method is primarily intended to determine the propensity for materials to crack or otherwise fail at flexing creases. However, it can also be used to assess if leathers are likely to produce salt spue.

The test can be conducted with either wet or dry specimens at room temperature, or with dry specimens at sub-zero temperatures. The method is applicable to all flexible materials – in particular those used to manufacture uppers and linings of footwear such as leathers, coated fabrics and textiles.

In terms of water resistance testing on materials, the contrast between the two main tests is very similar. SATRA TM171:2017 – ‘Resistance to water penetration – penetrometer test’ is conducted in many laboratories around the world. This uses, essentially, a ‘crumple action’ flex machine, with the sample mounted in a tray of water. There is also a means of detecting penetration – visual or electronic. SATRA TM171 is required in many safety footwear specifications. However, the shape of the flex creasing formed is different to a natural vamp flex that is used in SATRA TM25.

In a similar way to SATRA TM25, SATRA TM34:2019 – ‘Resistance to water penetration – Maeser test’ (figure 3) is designed to specifically recreate the flexing that occurs in vamp uppers and gives a far greater correlation to actual footwear. Hence, it is our preferred test.

Sole flexing

There are two popular tests to determine sole flexing characteristics. The first of these is SATRA TM161:2004 – ‘Bennewart flex test – resistance to cut growth on flexing’ which is mentioned in many safety footwear specifications. In this method, a sole is repeatedly flexed over a mandrel. One of the features of this test is that the sole is only flexed at one specific point. This means that only a very small area is tested rather than the whole sole, with all the additional stresses that would induce.

Alternatively, SATRA TM133:2017 – ‘Resistance to crack initiation and growth – belt flex method’ is SATRA’s preferred method. In this test, multiple samples/specimens can be affixed, either with adhesive or sewn, to a continuous belt. The belt is stretched between two mandrels (much larger than in SATRA TM161) and the belt is driven. The smaller of the mandrels is of a diameter that replicates footwear flexing. In fact, several diameters are available.

Whole footwear water resistance

The SATRA preferred test to evaluate whole footwear water resistance is SATRA TM230:2017 – ‘Dynamic footwear water penetration test’ (see figure 4). While there are more rapid tests, such as the alternative SATRA TM77:2017 – ‘Flexing machine – water penetration test’, SATRA TM230 creates much preferred conditions.

It combines a flexing action which is gentle on startup if the sole is particularly stiff and the flexing takes place at a normal walking pace. This allows immersion time to feature as part of the testing. Long immersion times often reveal flaws and weaknesses, leading to failure that more rapid testing will miss.

Light fastness

Another preferred footwear test is SATRA TM160:2025 – ‘Colour fastness to light from a xenon arc’. Although there are many alternatives, SATRA TM160 – rather than use just one wavelength of light (ultraviolet) – is designed to replicate the full spectrum (for instance, as would be expected after prolonged exposure to sunlight in a shop window display).

If you request a particular test, do not be surprised if the technologist asks why you have chosen that one. Of course, it may be that the method is included in a standard or a specification. However, if it is not, a more appropriate alternative might be available. SATRA technologists have access to a knowledge base stretching back over a century and will recommend the most relevant and applicable test that should be used for your individual application.

Publishing Data

This article was originally published on page 14 of the January 2026 issue of SATRA Bulletin.

Other articles from this issue »

---