TÜV Rheinland Blog - Insights from Asia and Africa

The Hidden Journey Behind a Pair of High Heels

Posted by TUV Rheinland on May 1, 2017 10:48:03 PM
TUV Rheinland

Every woman’s wardrobe is always short one pair of shoes. Be it for business meetings or for window shopping, for many women matching footwear is an essential part of their attire. However, did you know that there is a hidden journey behind every pair of beautiful heels that you see?

Good high heels must not only look good and go well with any attire. What’s more important is how comfortable they are to wear. Beauty and risk often go hand in hand. High heels have become a fixture in reports on recalls issued by Western governments every year. These high heels were all recalled for potential or proven risks to human safety.

The recall reports mention the presence of the chemical substance Hexavalent Chromium in the leather and soles of the high heels. Hexavalent Chromium can not only trigger allergies in the user but is also a recognized carcinogen. Such products do not conform to the EU's REACH (Registration, Evaluation, Authorisation and restriction of Chemicals) regulations.

The number of high heels recalls is quite significant. What high heels design and production processes may contain safety issues? According to experts at TÜV Rheinland, the safety of high heels can be divided into two areas: chemical and physical. Chemical looks at the materials used in footwear while physical focuses on the design and quality of the footwear.


Chemical is the main reason for high heels recalls

Generally, the materials used in footwear include leather, textiles, soles, PVC, and metal. The purpose of chemical testing is to ensure that products do not contain substances harmful to the human body or those that can trigger allergies or cause cancer.

  • Leather: Targeted chemicals include azo dyes, Pentachlorophenol, Formaldehyde, Hexavalent Chromium, and dimethylfumarate.
  • Textiles: Similar to leather. Basically azo dyes and Formaldehyde.
  • Metal: Refers mostly to the metal fittings on high heels. Nickel or lead content can cause allergic reactions and poisoning.
  • Soles and PVC: Testing looks for high-risk materials such as Total Cadmium, Phthalates, Organic Tin, and Polycyclic Aromatic Hydrocarbons. Sometimes, this is due to contamination from the adhesive used to attach the soles.



Physical is the Key to Comfortable High Heels

The harm caused by chemicals is something that consumers can’t see and is therefore less likely to notice (except those prone to allergies). The design and quality of the footwear itself has a direct impact on consumer purchasing decision. Factors include how the heel is secured, the appropriateness of heel height, how easily the soles become detached, and their wear-resistance. All of these factors are critical to the comfort of the high heels. High heels place a certain amount of torque on the knee and ankles. They squeeze the tip of the foot while also having an effect on the tendons, ligaments and spine. Over time, this can lead to rheumatism, bunions, back pain and spine problems. It is therefore important for high heels to pass the physical design standards. What are the physical quality tests that high heels must undergo?

1. Heel durability testing

Materials differ in their brittleness and plasticity. Testing is generally based on BS EN ISO 19956, SATRA TM21 and BS 5131 4.9 (Footwear - Test Methods for heels - Fatigue Resistance). These simulate the continuous impact energy on the heels from people walking at a normal pace and are suitable for all types of heels. The tip of the heel is tested with impacts that have a force of 0.68J each. Testing of the sample continues until the amount of damage makes it impossible (record the number of impacts required until write-off). Ultimately, the heel is subjected to 20,000 impacts and then assessed on overall wear.

2. Heel impact testing

High heels can sometimes be subjected to accidental impacts when worn. Applicable standards include BS EN ISO 19953, SATRA TM20 and BS 5131 4.8 (Footwear – Test Methods for heels - Resistance to Lateral Impact). These standards test how much force high heels can withstand from accidental impacts. Testing involves subjecting the tip of the heel to increasing levels of force up to a maximum impact energy of 18.3J. The amount of energy at which the heel breaks or becomes too bent for testing to continue is then recorded.

3. Dynamic stability testing of the entire high heel

TÜV Rheinland has its own specialized testing method. A fixed amount of force is applied to the heel each time along with a certain amount of lateral movement. The process is repeated 100,000 times. At the end of testing, wear to the heel and how well it remains attached to the sole is assessed to determine whether the footwear remains serviceable.

4. Heel and sole attachment strength test

Our testing standard is based on BS EN 12785 and SATRA TM113 (Measurement of the strength of attachment of heels to footwear and the backpack rigidity of such footwear). A tensile-testing machine is used to pull on the heel and sole at a fixed rate. The maximum force required to pull the heel from the sole as well as level of permanent deformation to the footwear is then recorded.

You had no idea that so much chemical and physical testing is involved behind every pair of beautiful and safe high heels? Wearing high heels is not a very comfortable experience for many women. It can also lead to back pain. Fashion or comfort? You should start by choosing safe footwear.

Topics: Products