The story of cork

THERE´S SO MUCH TO KNOW ABOUT CORK!

Cork is a natural material derived from the cork oak tree. It has a history of use dating back for thousands of years, and as with so many natural products, it is proving to have a wide range of applications in the modern world.

What Exactly is Cork Anyway?

Simply put, cork is the outermost layer of bark of two different species of oak tree that grow in the Mediterranean and Iberian region. It is harvested when the tree reaches 20 years, and then every 9 years after that. The productive life of the tree averages about 150 years.

What Makes it so Useful?

Cork’s honeycomb like structure is full of empty cells, which makes it very lightweight. With its low density, it floats on water, and it is also excellent for cushioning as well as shock and sound absorption. It is fire resistant, flexible and not affected by rot or insects. It can be molded into virtually any shape, and is harvested using environmentally sustainable methods. With all these features, it truly is an amazing material.

Cork Through the Ages:

Cork has been used for thousands of years as a stopper in bottles. It has even been found in the tombs dating back to ancient Egypt. Ancient Greeks and Romans also made good use of it, and it was found use as floats for fishing nets, sandals, wine bottle stoppers and even personal flotation devices for fishermen. Villagers used it to build their homes, as its insulative properties kept them warm in winter and cool in summer. It also made the floors soft and comfortable to walk on and was resistant to attack from insects and other pests.

As the years went on, cork continued to find its main use as a bottle stopper, and at a time when wine or beer was safer to drink than most water, this was vital. Up until the mid 1700’s, it was usually harvested from where it was growing naturally, but its increasing use led to it being purposefully cultivated. Starting in 1688, Pierre Perignon used corks held in place with wire to seal bottles of his latest creation, champagne.

In 1892, the mass produced cork lined crown cap lid ( better known as a bottle cap) was invented by American William Painter, who became very wealthy from his invention. It was the industry standard until 1955, when it was replaced by the plastic stopper.

A German company developed a method in 1890 for using waste cork. They combined it with a binding agent so that it could be rolled into sheets to be cut into whatever shape was desired. This is called agglomerated or compound cork. John Smith discovered that, by using heat and pressure to release the naturally occurring resins, he could create a conglomerate of cork particles that didn’t need any binder. Charles McManus found a method of producing agglomerated cork that could be used to line bottle caps, and since then, others have carried on in his footsteps and found new and innovative ways of reusing waste cork and the byproducts of its production.

How is Cork Harvested?

Cork is harvested from the oak trees using a specially designed hatchet. Vertical and horizontal cuts are made through the bark, being careful not to hurt the living part of the tree. Usually, this is done on the trunk, but on some larger trees, the lower branches are also utilized. The layer is then gently removed using the wedge shaped side of the hatchet.

The slabs are the left to cure outside in the sun and rain for up to 6 months. This strengthens and flattens them. After that, they are treated using heat and water to remove dirt and unwanted chemicals. This leaves the cork more flexible and soft.

Once it is ready, the poorer quality cork is scraped away, and the remaining portion is left to cure and dry in darkness and with controlled humidity. This high quality material will be made into wine stoppers, while the lower quality cork will be ground and made into agglomerated cork.

The fact that cork trees aren’t harmed when the cork is collected, and that better quality cork is produced on older trees means that producers are best served by allowing the trees to grow undisturbed in large stands. This provides excellent habitat for local wildlife, some of which, like the Iberian lynx, is in danger of extinction.

How is the Cork Made Into Wine Stoppers?

The cork is placed in a steam chamber to soften it, then the slabs are cut into strips as wide as the intended bottle stoppers. The corks are then punched from the slab using hollow tubes. If a tapered shape is desired, they will be pared down using a machine with a blade that rotates at a very high speed. The corks washed, bleached and sterilized. They are then dried and stamped with an identifying label and may be treated with paraffin or silicone and packed into airtight bags.

What About Agglomerated Cork?

The cork is broken into small pieces, then ground to the desired consistency. It is screened and packed into a mold, Pressure and high temperature steam cause the release of natural biding agents, which hold it together once it is removed. Compound agglomerated cork uses a similar process, but an additional binding agent is used and it is heated more slowly in the mold.

Once removed form the mold, the blocks are allowed to dry and cure before being cut to shape for its intended use. It may be shaped into disks, tubes, sheets or any other shape that is desired.

What Happens to the Leftovers?

The manufacture of cork is quite environmentally friendly, and any waste products can be re-purposed. Any waste cork is ground up for use in agglomerated cork, and any cork powder can be used as fuel in the factory. Chemical by products such as tannins, hard wax, resins and phonic acid all have uses in the tanning, paint and cosmetics/toiletries industries.

In a modern world of synthetic materials, cork continues to lead the way. This amazing and natural material has a wide range of applications far beyond the oft thought of wine bottle stopper. With new ways to use it being thought of all the time, it is sure to continue to be an environmentally friendly favorite of manufactures and designers for many years to come.