Plastic has become ubiquitous in the material world, thanks much in part to its low cost and durability. Unfortunately, those attributes are also the problem. Plastic takes centuries to decompose and is polluting every realm of the planet.
For textiles, non-plastic options are easy enough to come by. For more durable goods where leather is generally used, consumers have a choice between vegan leather, generally made of plastic—or an animal product. For many of us, neither option is desirable. Enter cork leather!
Cork fabric is a natural material or leather substitute that is made from the cork oak tree. The bark harvested from the oak tree regenerates after the cork is stripped, making it a sustainable and biodegradable resource, and almost all cork products can be recycled.
Cork fabric is light, impermeable, compressible, and has low thermal conductivity. Cork material is used as a building material, in musical instruments, in rockets as insulation, packaging, shoes, furniture, and more recently, clothing and accessories.
The cork oak species (Quercus Suber) is native to the western Mediterranean basin. Portugal and Spain are the largest producers of cork. Portugal produces around 100,000 tons of cork per year, while Spain produces almost 62,000 tons.
How Is Cork Fabric Made?
The process of harvesting cork begins with the stripping stage. The stripping is done manually with a specially designed axe. The first stripping takes place when the tree is between 20 and 30 years old and does not meet the quality requirements to be used industrially. The next stripping is done nine years after the first.
The cork is boiled, marked, and cut. Afterward, cork planks are separated by quality. The cork will also go through a drying phase and be further washed and then treated for the industry in which it will be used. For cork fabric, the cork is left to dry for almost six weeks and is then boiled in water and flattened to create cork sheets. Cork fabric is produced from fine laminated sheets of natural cork or by gluing the cork to a textile or other base. Since cork is a fragile material, this second layer is necessary for the fabric to be used as a textile.
History and Uses
Though used in footwear thousands of years ago, the cork industry only started creating new materials out of cork for things such as furniture and coverings in the late 20th century, and cork fabric that is used in accessories and clothing has only gained attention during the 21st century.
Companies can create cork leather to replace animal leather in bags, backpacks, wallets, belts, shoes, and dresses or use the fabric for upholstery. According to one study looking at cork as a material in fashion, cork itself is not considered a true textile since an additive or second layer has to be added to the fabric since cork can be fragile. However, the bonding of cork with other fibers allows for thin layers of the material, which allows for the fabric to be easily sewn.
Is Cork Waterproof?
Yes, cork is waterproof. Cork is mainly composed of suberin and lignin, with each respectively representing 43% and 22% of the cork’s dry mass, and both polymers are highly hydrophobic, according to a study on cork quality.
Cork vs. Leather
Cork leather is favored over animal leather because of its sustainability and low environmental impact. Notably, cork can be used as a humane, plastic-free alternative to an animal product.
At the harvesting stage, which is done manually and with specialty tools, the cork industry has a low environmental impact because cork oak trees regenerate their bark after it is stripped. The trees are debarked in around another nine years to allow for enough growth time.
According to research comparing cork and leather, laminated cork has been shown to have lower water vapor permeability, lower air permeability, a higher abrasion resistance, and almost the same thermal abilities as animal leather. Leather was shown to be almost two times thicker than laminated cork, but the thermal resistance and thermal conductivity between the two materials were practically the same. A low air permeability means the fabric can protect from the wind, while a low water permeability protects from water. A higher abrasion resistance means that the material is able to resist wear.
Is Cork Fabric Durable?
Yes, cork fabric has high tensile strength in warp direction, and high abrasion resistance, according to a paper on the application of cork substrate in clothing.
Sustainability and Environmental Impact
Cork is a renewable resource; it is recyclable and also sequesters carbon dioxide. The Portuguese forest alone, which holds 32% of the global cork oak forest area, has sequestered 4.8 million tons of carbon dioxide, according to a study on cork sustainability. In addition, when the bark from a cork oak tree is harvested, it will produce between 250% and 450% more cork than a tree that hasn’t been harvested. This cork harvest stimulates growth, which will continue to sequester more carbon dioxide. The same study found that around 182,000 tons of carbon dioxide will be fixed with the production of 350,000 tons of cork.
The cycle of cork oak forests can be divided into four stages, according to an analysis of cork extraction in Catalonia.
- The first stage is planting, but this does not happen in Catalonia because of the natural regeneration of the trees.
- Cork stripping is the second stage; the biggest environmental impact occurs at this stage because of the transportation of workers and the cork. The contribution is to the global warming potential (GWP) of the environmental impact assessment, and in total, can contribute 145 kg of carbon dioxide equivalent for one ton of cork extracted.
- The third stage is scratching, which happens three years after the cork is stripped and is done to promote future cork extraction. However, some areas do not do this to reduce costs. The impact here is transportation, but it is less than that of cork stripping.
- The final stage is shrub clearance and road management. This prevents interspecies competition, reduces fire risks, and, if needed, opens new roads for access to the forest. This final stage will contribute to the GWP of the environmental impact assessment at 33 kg of carbon dioxide equivalent.
Broadly speaking, cork is sustainable, but the specific materials and techniques used in creating cork fabric vary widely. For example, some companies use Global Organic Textile Standard (GOTS) certified cotton to create their fabric. GOTS is a worldwide textile processing standard that is used for organic fibers and incorporates social and ecological criteria in the process.
Meanwhile, some companies treat their fabric with water and stain repellents that may contain perfluorinated compounds (PFAS), which are known as “forever chemicals” in the environment. The United States Environmental Protection Agency (EPA) notes that “scientific studies have shown that exposure to some PFAS in the environment may be linked to harmful health effects in humans and animals.” (Other sources are more conclusively negative.)
Cork products should list whether or not they use fabric repellent and what backing is used in their products.
There is no certification system yet for cork fabrics, but Rainforest Alliance is attempting to certify cork forests in Spain and Portugal and certified its first cork forest in Morocco in 2007. The sustainable forest certification promotes environmental and socially responsible management of forests.
Pros and Cons of Cork Fabric
Durable and sustainable: Laminated cork has a higher abrasion resistance in comparison to leather.
Water resistant: The properties of cork allow it to be water resistant and have low water vapor permeability.
Environmentally friendly: Cork forests can sequester 5.7 tons of CO2 per hectare per year, and cork is a renewable source. Cork trees also maintain carbon stocks for a long period of time.
Treatment: Depending on the type of fabric, cork fabric can be treated with harmful chemicals. It can also be backed with textiles that make it hard to recycle.
When done right, cork fabrics and cork leathers hit all the right notes. Cork offers a high-performance, plant-based material as a sustainable alternative to animal leather and planet-polluting plastics. We’ll pop the cork to that!