Cork (material)

It is the phellem layer of bark tissue which is harvested for commercial use primarily from Quercus suber (the cork oak), which is native to southwest Europe and northwest Africa.

The montado landscape of Portugal produces approximately half of the cork harvested annually worldwide, with Corticeira Amorim being the leading company in the industry.

It is a material whose applications have been known since antiquity, especially in floating devices and as stopper for beverages, mainly wine, whose market, from the early twentieth century, had a massive expansion, particularly due to the development of several cork-based agglomerates.

[4] In China, Egypt, Babylon, and Persia from about 3000 BC, cork was already used for sealing containers, fishing equipment, and domestic applications.

[5][6] In the second century AD, a Greek physician, Dioscorides, noted several medical applications of cork, mainly for hair loss treatment.

The innovation of using cork as stopper can be traced back to the late 17th century, attributed to Dom Pierre Pérignon.

[3] There are about 2,200,000 hectares of cork oak (Quercus suber) forest in the Mediterranean basin, the native area of the species.

Cork oak forests also prevent desertification and are a particular habitat in the Iberian Peninsula and the refuge of various endangered species.

The Corticeira Amorim's study, in particular ("Analysis of the life cycle of Cork, Aluminum and Plastic Wine Closures"), was developed by PricewaterhouseCoopers, according to ISO 14040.

This is the most delicate phase of the work because, even though cutting the cork requires significant force, the extractor must not damage the underlying phellogen or the tree will be harmed.

A good extractor needs to use a firm but precise touch in order to free a large amount of cork without damaging the product or tree.

The cork is stacked in piles in the forest or in yards at a factory and traditionally left to dry, after which it can be loaded onto a truck and shipped to a processor.

[19] Cork's bubble-form structure and natural fire retardant make it suitable for acoustic and thermal insulation in house walls, floors, ceilings, and facades.

[21] As late as the mid-17th century, French vintners did not use cork stoppers, using instead oil-soaked rags stuffed into the necks of bottles.

[24] Because of the cellular structure of cork, it is easily compressed upon insertion into a bottle and will expand to form a tight seal.

The interior diameter of the neck of glass bottles tends to be inconsistent, making this ability to seal through variable contraction and expansion an important attribute.

For example, screwtops are generally considered to offer a trichloroanisole (TCA) free seal, but they also reduce the oxygen transfer rate between the bottle and the atmosphere to almost zero, which can lead to a reduction in the quality of the wine.