The natural rubber crepe sole comes from an indigenous South American tradition. The sole is not so common anymore because of its complex manufacturing that involves a handcrafted process, and requires expert knowledge and lots of experience.
The Natural Crepe Sole
The process of creating a natural crepe sole
The production of the natural crepe sole is a process free of chemical substances with a low environmental impact. First, sap from the tropical rainforest Hevea-tree is collected. Thin stripes are cut into the tree’s bark enabling it to release a latex substance, which serves as the raw material for the sole. Don’t worry, this process does not exploit the tree. On the contrary, this method of harvesting sap helps the tree thrive and makes it stronger. The next step consists of filtering the rubber latex. Then acetic acid (a naturally occurring, bio-degradable substance) is added so the latex can curdle and be sliced into blocks. This cheese-like mass still contains excess water, so it is pressed in between rollers to help squeeze out the liquid. This results in a 1cm thick crepe rubber sheet that is continuously pressed and rolled until it becomes 1mm thick. The final step is to put 12 of these sheets together into a mold… And there we have our sole!
How to take care of a natural crepe sole
Crepe soles are self-sufficient and low maintenance. If you want to enjoy them for a long time, you can opt for some easy-care tips such as avoiding exposing them to extremely hot temperatures and cleaning them once in a while. You can mix some water and a few drops of clear detergent (preferably an eco-friendly option to avoid extra water pollution). Make some foam and gently apply with a sponge or brush, if the dirt is hard to remove. You can also use curd soap and apply it directly into the sole. Wash it off with clean, cold water and let it dry. That's it! Do not use abrasive solvents, as they might permanently damage the sole.
- Rubber crepe is incredibly flexible and resistant, offering support for long walks
- The cushioning bubbles in the crepe sole absorb shocks in every step, so they are very comfortable
- Natural crepe is an open-pored material that offers excellent grip on slippery surfaces
- Thanks to its compressed structure, these soles provide longlasting durability
- Crepe soles are also biodegradable
- The production process of natural rubber is more costly
- Natural rubber has poor resistance to hydrocarbons, fat, oils, and greases
The Rubber Sole
When we first started with our first huaraches, we used rubber soles as they are very cheap and easily available. However, we quickly switched to natural materials to make sure our shoes are biodegradable. In rare cases, we do use normal rubber soles. But these are made of upcycled airplane tires and are not produced with virgin materials.
The process of creating a rubber sole
Rubber soles are made through a process called vulcanization. It consists of mixing natural rubber with curing agents, such as sulfur or peroxide. The mixture is placed into two shoe molds to create the insole and outsole. The molds are heated for a short time. Once out of the oven, the excess rubber is cut away. Then the insole and outsole are fused to form the finished product.
Rubber sole manufacturing can lead to air, water, and odor pollution. Shockingly, the production process of synthetic rubber results in more waste than the volume of rubber produced, according to the WWF. And this waste includes forms of eruptive organic compounds, some of which are suspected to cause cancer.
How to take care of a rubber sole
Rubber soles don't require as much care as natural and leather soles since they are water-resistant by nature. You can clean them with soap and water to keep them looking clean and to avoid tracking dirt into your home. As with all soles, it's best to keep them away from heat sources to avoid the material cracking.
- Rubber is often quite flexible off the bat. This results in a minimal break-in period, making your shoes comfy from the start
- The water-resistant aspect of rubber soles are handy for rainy days or muddy terrain
- Rubber soles are anti-slip, making them ideal for walking on slippery surfaces and wet surfaces
- Most shoes with rubber soles are slightly heavier than shoes with leather soles
- Once discarded, the soles will not biodegrade
- Shoes with rubber soles are generally thrown away when the sole wears out
The Leather Sole
Just like our shoes' upper material, our leather soles are made of vegetable tanned leather.
The process of creating a leather sole
Leather soles are made by salting and tanning animal hides, which turns them into leather. Leather can be vegetable-tanned or tanned using chemicals, like chromium. You can read more about the difference and their environmental impact in this blog post. After the leather is cleaned and dried, the soles can be cut by hand or laser to different shoe shapes and sizes.
Generally, leather production requires a lot of water and can lead to water pollution.
How to take care of a leather sole
With a leather sole, you must take care not to step in puddles, as it wears out much faster when wet. However, when the sole leather is too dry, it also wears out more quickly. You can address this by applying a mild polish to the sole once a month. This will keep it moistured. To finish off, you can also apply a leather-conditioning cream. Read more about leather care here.
- With use, the leather sole molds to your foot, making the shoe increasingly comfortable
- Vegetable-tanned leather is biodegradable
- Leather is a breathable material, allowing your feet to keep cool and dry
- In terms of thermal regulation, leather soles are great for summer shoes as they protect your feet from heat better than rubber soles
- Leather soles can be resoled, which extends the life of the shoe
- Leather is more rigid and will take more time to break-in
- The material may wear out more quickly and need replacement more often than (natural) rubber soles
- In conditions of high humidity, leather does less well than its components
Which sole is right for you?
What sole fits you best depends on your personal needs and values. Natural rubber soles are great walking shoes as they are very flexible, shock-absorbent, and offer grip on slippery surfaces. Rubber soles have great water resisting properties. And leather soles are especially great for warmer weather, as they are very breathable and regulate temperatures well.
If you are concerned with the environment, we recommend going for a biodegradable natural rubber, leather sole, or a rubber sole made of upcycled materials. But whatever you choose - the most important is to choose high-quality products and give them the care they need to make them last and enjoy them for years to come.
Written by Jessica Teeuw