Cork Fishing Float

This characterful, warm and tactile Mediterranean material may be most familiar as the chewy, beige bung that stands in between you and a glass of wine, the insulating coaster that stops your hot tea from cracking a varnished table, or the bulletin board where you pin up that important reminder to feed the neighbour’s cat. Without cork we would be a sober, heat-crazed and forgetful bunch!

Cork’s versatile repertoire spans applications as varied as life jackets, fishing floats, anti-ageing creams and orthopaedic shoes. What’s more, cork oak acorns make an excellent foodstuff for growing goats, and are particularly beloved by Spanish pigs, contributing to the sweet flavour of Iberico ham. 

Cork is the bark of the cork oak tree (Quercus suber); a slow-growing, long-lived oak that mainly grows in the savannahs of southwest Europe and north Africa. All trees have a thin layer of cork in their bark, developed as an adaptation to protect against fires, but in this particular oak it grows to form layers up to 30 centimetres thick. The cork oak tree can live for up to 250 years, whilst the material we know and love is skilfully and carefully harvested from the stem every nine years or so, without harming the tree. This renewable, spongy coat has a honeycomb structure that consists of billions of tiny, hollow, pentagonal or hexagonal cells. The cell walls are made from a fatty biopolymer called suberin (which is also responsible for the tough skin and long storage life of the potato) and are filled with an air-like gas that makes up 90% of the material’s volume. This waxy, hollow, honeycomb structure gives cork its unusual array of properties: impermeability to liquids and gases, strength and light weight, flexibility, compressibility and excellent thermal and acoustic insulation. 

These extraordinary properties are revealed by cork’s long catalogue of uses from antiquity to today. For example, Roman soldiers made the most of its ability to thermally insulate by using cork in their helmets to protect them from the sun, and small Roman women are thought to have made the most of its strength, light weight and compressibility by fashioning some of the earliest platform shoes. It’s still employed in wearable items today in the soles of Birkenstocks and combined with cloth to make everything from couture handbags to neck ties. Cork’s architectural career also began with the Romans, when it was used as insulating roof covering. Fast-forwarding to today, it features domestically in the form of linoleum flooring (whose retro charms are thanks to a composite of cork, oxidised linseed oil and gum pressed onto flax sheets), and on the international stage in Herzog & de Meuron and Ai Wei Wei’s 2012 Serpentine Pavilion, Superflex’s 2018 installation of a forest of cork swings in the turbine hall at Tate Modern, and most recently, an entirely cork house that was designed and prototyped here at UCL’s Bartlett School of Architecture.

Cork’s water-repelling tendencies, floating power and durability make it ideal for marine applications where buoyancy is vital. This trustworthy and uplifting natural foam was first used in 3000 BC for early Chinese fishing floats, and was still in service at the end of the 1700s, surpassing rivals such as horse hair and balsa wood to become the filling for the first life jackets. Cork has long-proven its worth to sailors and naval types, finding use as floats to mark the position of an anchor, as ‘tampions’ to stopper the barrels of guns and prevent dust and salt water getting in, and as a filling for barricades to protect against enemy fire. To this day, cork is still a favourite of fishing folk: cork bobbers slosh around on the surface to attract the fish, whilst also adding more life to the attached artificial lure dangling below.

For much more on cork, check out our long-form blog post on this quietly competent natural foam that has been supporting sailors, scientists, architects, fishing folk, medics and monks for millenia.