For the traditional producers of Spain and Portugal, the death knell of the industry really would spell the end of life as it has been known for many centuries. The two countries together contribute 80% of the world’s production and export of cork – Spain accounting for 26% and Portugal a whopping 54% – more than anywhere else on earth. And, although cork is material with many other uses than plugging wine bottles, the fact remains that some 60% of all cork production goes into stoppers for wine bottles.

It comes as little surprise, therefore, that intense argument rages over the advantages and disadvantages of the traditional material for stopping wine bottles and the benefits of a growing list of alternatives.

The traditional stopper has just that advantage, of course. It has a tradition stretching back many thousands of years – with records of cork’s use to seal containers by the Egyptians. It was similarly used by the Greeks and the Romans also. It wasn’t until the 1600s, however, that the real milestone was set for using cork as a bottle-stopper. This was when the French monk, Dom Pérignon, hit on the idea of using the material as a wine closure. Previously, casks containing sparkling wine traditionally had been plugged by wooden stoppers wrapped in olive oil-soaked hemp. Dom Pérignon observed that these stoppers often popped out. He successfully swapped the conical plugs for cork stoppers and cork soon became essential for wine bottling.

So successful was the idea, in fact, that a whole industry blossomed in the wake of Dom Pérignon’s innovation and, fuelled by a rapidly growing wine industry, demand for cork increased, sending ripples into Catalonia in Spain. The world’s first cork stopper factory opened in around 1750, in Anguine in Spain, marking the beginning of the industrial application of cork. Cork stoppers arrived in Portugal around 1700. Some 70 years later they were used in cylindrical bottles in Oporto, allowing the wine to mature slowly in a glass receptacle for the first time. The spread of mass-produced glass bottles with a uniform neck and opening helped to advance the acceptance of cork stoppers, not just for wine but a wide range of liquids.

Production boomed in the last quarter of the nineteenth century. Between 1890 and 1917, the industry’s workforce more than doubled and by 1930 it had increased fivefold, to a total of 10,000 workers. By this time Portugal had become the world’s leading cork producer, a position it holds to this day. Today, however, the industry is estimated to employ some 100,000 people, 37,000 of whom are directly involved in harvesting.

The harvesting of cork is, in fact, a long term affair. It is, of course, the bark of the cork oak tree that is harvested to make cork products and the harvesting is done without killing the tree. Although this process allows the cork oak a productive life of some 150 years, the tree is not ready for its first harvest until it is about 20 years old. The first harvest yields a poor quality cork, which can only be used for agglomerated cork products. Subsequent harvests occur at nine-year intervals, when the useable bark reaches a thickness of about 1-2 inches (2-5 cm). The harvest from a young tree yields about 35 lb (16 kg) of cork, while the yield from mature trees can reach 500 lb (225 kg).

Currently, the promotional campaigns directed at saving the cork industry concentrate largely on the ecological sustainability of the production methods. They are promoted as being environmentally because production is entirely organic and its products and by-products are recyclable.

Demand for cork saw a significant resurgence when more wine began to be bottled and sealed with cork, rather than being sold in bulk. Ironically, though, it was just such a resurgence in demand that has helped fuel the search for alternative materials for wine stoppers. Because the long supply-cycle makes the supply curve especially inelastic and top-quality cork very expensive, many producers turned to offering a poor-quality product to meet the demand. This, in turn, increased the incidence of TCA contamination of the cork (and, therefore, the wine in the bottle). TCA – or trichloroanisole – is a harmless and naturally-occurring but foul-smelling ingredient of cork and has rapidly become one of the primary causes of cork taint in wine.

Frantic efforts have therefore been made by the cork industry to reassure its customers with tighter quality-control measures. Governments have also stepped in to try to avert the collapse of the industry. In March 2006, for example, the Spanish government outlawed the use of alternative wine closures in 11 of Spain’s wine producing regions as part of their (Denominacion de Origen) D.O. regulations.

Nevertheless, the costs and risks inherent in continuing to use the traditional, natural product continue to fuel the search for alternatives that are acceptable to wineries and customers alike.

Synthetic corks, for example, are made from plastic compounds that are designed to look and “pop” like natural cork, but without the risk of TCA contamination. The US company Supreme Corq is the world’s largest producer of synthetic corks. As anyone who has struggled with this type of stopper can testify, however, these can be difficult to extract and difficult to put back in again to reseal the bottle. Some wine-tasters report that synthetic corks can impart a slight chemical flavor to the wine. What is more, some studies have shown that synthetic corks allow the highest levels of oxygen permeation compared to natural cork and other stoppers, thus offering the lowest protection against oxidation of the wine. Finally, of course, most synthetic corks are environmentally unfriendly, in that they are made from non-biogradeable materials.

Screw caps or “Stelvin caps” are the familiar tops made from tin or aluminum that threads onto the bottleneck. They are most popularly used by New Zealand wineries, where an industry-wide initiative promotes the use of screw caps instead of cork. Screw caps form a tighter seal and can keep out oxygen for a longer time than either natural or synthetic cork. Their key drawback, however, is that consumers still tend to pereceive screwcaps as being for ‘cheap’ wines (regardless of the price tag).”

Vino-Seal is a plastic or glass stopper made by Alcoa. Since its introduction into the European market (under the name Vino-Lok) in 2003, over 300 wineries have utilized Vino-Seal. Although the glass stopper and seal prevent oxidation and TCA contamination, they are relatively expensive (each plug costs about 70 cents) and manual bottling is needed anywhere outside Europe, because of the lack of compatible bottling equipment. Nevertheless, the design has won a Worldstar Award for Packing Excellence from the World Packaging Organization.

Zork will probably be the least familiar name and is a closure from South Australia invented by Conor McKenna and developed by industrial designer John Brooks. Zork creates the “popping” sensation that natural cork has when opening but with protection against TCA similar to a screw cap. Made from recyclable food grade polymers, Zork can be removed without the need for additional tools and can be easily resealed.

The Zork stopper is made up of three parts. A robust outer cap provides a tamper-proof clamp that locks onto the the lip of a standard bottle, an inner metal foil that provides an oxygen barrier similar to a screw cap, and an inner plunger which creates the ‘pop’ on extraction and reseals after use. Zork can be applied by hand, or at high speed using standard capping equipment with minimal low cost modifications. Several American, Australian and European contract and mobile bottlers now have the capability of bottling with Zork.

Even the traditional crowned bottle cap has been used in the sparkling wine industry as a stopper during the bottle fermentation process (méthode champenoise). Usually the cap is replaced with a cork before shipping, though recently some producers have been releasing wines using the crown cap as their closure. The crown caps provide a tight seal without risking cork-taint. Although easier to open, crown caps eliminate part of the ceremony and mystique of opening a sparkling wine and – as with the screw-top – immediately tend to brand the contents as “cheap”.