Rao and I are literally scouring the earth seeking eco-friendly and sustainable materials to use in constructing Common Soles footwear.  We’ve come across all sorts of incredible product as well as some down-right scary stuff.  We’re finding materials both here in Massachusetts as well as across the ocean. Building on our Oct 22nd blog post on Making Eco-Friendly Flip-Flops here is an update on some of the materials and construction techniques we hope to be working into our line moving forward. This post is also essentially Part 3 of a series I am writing on sustainable footwear here on our blog. Enjoy!

Rice Rubber Outsole: This stuff is amazing. The outsole is the very bottom of footwear, the part that connects with the ground. Most traditional outsoles are made from rubber or PU (polyurethane). Rice Rubber is a blend of several happier ingredients. It’s a base of natural latex rubber mixed with SBR or Styrene Butadiene Rubber. SBR has been used for over 60 years in all sorts of applications such as tires, shoes, and gaskets. The blend is necessary for durability and longevity (Remember – durable footwear has a longer useful life = fewer pairs need to be manufactured). Rice husks which are a byproduct of the food industry and typically discarded after harvesting are then mixed in with the rubber. The rice husks displace a good portion of the rubber needed as well as add strength to the mixture. Similar to how gravel is added to cement to form concrete. The resulting product is not only a more eco-friendly alternative to traditional rubber soles, but it looks darn cool!

Cork Blend Footbed: Another amazing product for footwear. Cork is wonderful. It is a sustainable product of the Cork Oak tree, and as I’m sure you know used in a myriad of applications from footwear – floor tiles – wine stoppers!  This footbed material we found is incredible. It’s consists of a cork top-sheet mounted onto a layer of foam that is mixed with bits of cork. The resulting product is both kind to your foot and the environment. The cork top-sheet is the portion of the footbed in contact with your skin. Having this natural material in contact with your skin is good.  It’s all natural as well as hydrophilic, which means it wicks the moisture (sweat) away. This nets a more comfortable wearing experience than what other materials can offer. Using cork in footwear or flip-flops is not anything new – its how it’s used is what we are looking to innovate around. The foam sheet the cork is mounted on is a cork infused foam. The foam is recycled PU foam. I mention PU above. The cork bits displace a good amount of foam needed just as the rice husks do. Same deal as the concrete example. 

Leather: Leather is the tanned skin of an animal. The skin itself is quite sustainable as we eat quite a few animals such as cows, pigs and goats that all produce skin suitable for shoe leather. Let’s put the whole eating animals debate aside for now because I know not all of you eat animals, and many of you think it’s cruel. What many of us do agree on however is that animal skin is sustainable and a good alternative to synthetics for the use in footwear uppers, or in the case of a flip-flop or sandal, the straps.  

It’s the tanning process that we need to pay attention to here. Traditional industrial leather tanning involves the uses of all sorts of polluting and heavy chemicals and processes. Minerals such as chromium are used which eventually leach into water supplies and thus pollute. Vegetable tanning is the original method and involves using tannin which is where the root of the word “tanning” originates. Tannin is made from the bark and leaves of many naturally occurring plants. Tanning is the process that alters the physical state of the skin turning it from rapidly degrading rawhide into long-living leather that can be re-used. Rao is quickly becoming a leather expert during his travels throughout India. Here is a pic of some of the goods he’s come across that we plan to integrate into our line moving forward.

So that’s three big ones for your reading pleasure. We’re also working on the footwear assembling process which involves the use of petroleum based rubber cement. Water based cement is the clear choice for us moving forward. Further, it’s reducing the total amount of cement needed without taking away from the overall quality of the finished product. I’ll write more on that later. 

Loving the learning process this has become!
-Dave