Cork and rubber are natural materials widely used in shoe-sole construction. Both materials are ideally suited for this application, given their inherent properties and renewable nature. In some shoes, both materials are combined to enhance and augment one another, making for safe and comfortable footwear.
Old Rubber Tree
Rubber and cork are derived from trees. Rubber trees produce latex sap, which is converted into rubber shoe soles through various processes. Rubber is waterproof, provides good traction on a variety of surfaces and is relatively tough. Rubber content is often melded with leather on nicer dress shoes for increased comfort, while allowing the shoe to maintain the sleek lines imparted by a thinner leather sole. On some shoes, rubber is used in lieu of leather, molded to mimic the appearance of the traditional sole material while adding slip and moisture resistance.
Cork is found under the uppermost layer of cork trees. The material offers excellent rebound capacity given its spongy attributes. Cork is naturally odor-resistant and moisture wicking, making it a solid selection for shoe insoles as well. On many occasions, the natural benefits of cork is combined with the toughness and durability of rubber to make shoes that have a little extra life and slip resistance.
Since both cork and rubber are naturally occurring materials, they are also able to be recycled. Cork and rubber are purified and turned into new shoe soles, as well as other important everyday items made from materials such as flooring and tires. Both materials are naturally biodegradable, so even if the shoes make it into a landfill, they won’t take long to break down.
On Solid Footing
Cork, when used as a shoe insole, thermoforms to the wearer’s feet over time, i.e., heat and pressure from standing and walking in the shoe causes the insole to mold to the natural shape of the foot, reducing stress on legs, joints and backs. Rubber’s natural tendency to absorb shock also makes it a preferred sole material for those on their feet for long hours such as retail workers, nurses and military personnel. When both are used together, very little impact from normal walking transfers into the wearer’s legs and back, reducing pain from a long day.
References and ResourcesRainforest Alliance: Rubber Tree
Birkenstock USA: The Foot Health Benefits of Birkenstock Sandals, Shoes and Clogs
Cork Institute of America: Cork Properties
Woman's Day: 8 Secrets from Shoe Repair Shops
Financial Times: The Rubber Sole Is On the Rise
Orvis: Clearwater Navigator Rubber Sole Shoe