Wine corks

Excuse me waiter, this wine is ‘plasticked’..’Quack’ open another bottle.

A romantic candlelit dinner for two, a single rose adorning the table, soft music in the background. The impeccably attired wine waiter proffers the bottle and, receiving a barely discernable nod of approval, carefully removes the cork. It ‘quacks’.

It is not inconceivable that the romantic sound of a ‘popping’ wine cork will be replaced by the not-quite-so-endearing sound of a ‘quacking’ plastic one. The revolution has already started, and you may not have even noticed!

So, what are those cylindrical things that keep the wine in the bottle and why do we use them? What is ‘corking’? Where does cork come from, and what are the pros and cons of plastic corks?

The ancient Egyptians knew that wine must be stored in airtight and waterproof containers and used wax or a resin-like substance to seal their amphora jars. In the Middle Ages, wines were kept in casks and wooden stoppers wrapped in cloth ensured a better seal.

With the introduction of the glass bottle in the 17th century, wine producers were forced to become more imaginative. Glass stoppers were used in some areas, but they were expensive and impractical.

Then a certain Benedictine Monk called Dom Perignon came up with the idea of using cork to seal his bottles of sparkling wine and, slowly, corks became the standard way to seal bottles and ensure the easy storage of wine in glass.

What is cork?

Cork is the bark of the Cork Oak (Quercus suber), grown in plantations in Spain, Portugal and Algeria. All Mediterranean cork is sold to Portugal, where a small number of manufacturers produce about 80% of the world’s annual supply of wine corks (13 billion or so) and this industry accounts for roughly 3% of their GDP.

Why cork?

Natural cork is a material with an unusual property in that it does not expand laterally when compressed. In other words, it stays more or less the same width when it is squashed lengthways, thus making it possible to push it into the neck of a bottle. Most other materials swell outwards when compressed and would, therefore, jam in the neck. There is just enough outward expansion in a cork to make a good seal. In scientific jargon, cork has a Poisson’s Ratio very close to zero.

How is a cork made?

The bark is stripped from the tree and used to make the corks. This process does not damage the tree, in fact the trees become so accustomed to it that they can have serious problems if the bark is not removed. The bark re-grows, and after nine years it is ready to be stripped again. A mature tree can produce about 200kg of cork every nine years and for as long as 200 years.

Normal corks are just cylinders cut from the bark. It is first seasoned for six months or so, then boiled to kill any mould and insects. The corks are dried for three weeks then sliced into strips. From these processed strips, corks are punched out and polished.

Sparkling wine corks, by the way, are much more complicated. They need to be much stronger than normal wine corks in order to withstand the pressure created by all those fizzy bubbles. They are still cylinders, but appreciably wider. The cork is layered to provide extra strength and compressed laterally before being inserted into the bottle.

What is ‘Corked’ Wine?

Traditionally corks are bleached in chlorine, both to kill bacteria and to improve the cork’s appearance. However, a special mould (trichloranisole or TCA for short) can grow from the leftover chlorine. It obviously doesn’t affect all corks, and the exact reason for this is still not known, but it does affect up to 8% of wine bottles. I say ‘up to’ because there is some divergence of opinion on this matter.

Wine critics tend to suggest a ‘contamination’ figure of between 5% and 8%, whilst a study by the Wine and Spirit Association came up with 1.2%. They also suggested that more problems are caused by oxidization, air getting to the wine. Be that as it may, it is the TCA tainted bottles that are referred to as ‘corked’.

Although the cork is the prime source of TCA taint in bottled wines, it is not the only source. TCA contamination can occur at all levels of wine production from harvesting the cork (fungus in the pores of the bark) to wine storage to bottling.

Small amounts of TCA result in a flat, flavourless wine, larger amounts make the wine totally undrinkable. The taste has been likened to chewing a ‘wet carpet’, but not being into such things I can’t comment, except to say there are obviously some very strange people about.

Corked wine is the prime reason for the tasting ‘ritual’ in restaurants. You will certainly know if your wine is corked and you should never be afraid to send it back and request another bottle. It is also one of the main reasons for the increase in popularity of the plastic cork, as wine manufacturers have to bear the cost of the, up to 8%, ‘undrinkability’ factor.

Plastic corks

One solution to the problem of corked wine is to use corks made of plastic. These are becoming increasingly popular with wine manufacturers, since they do not suffer as much from the problem of TCA and are cheaper.

Although they are slowly catching on, it will probably be quite some time before the old-fashioned cork bites the dust. In general, one bottle in twenty now has a plastic cork.

In the UK, the world’s largest wine importer, the figure is one in three! This came about, in the main, when Safeways Inc UK and Marks and Spencer initiated a natural cork ban and signed a deal with an American company to supply plastic stoppers.

Reaction from the cork industry

Portuguese cork manufacturers have responded by promoting cork’s unique properties and spending an estimated 400 million euros on improving quality. They plan to invest a further 500 million in their attempts to save the cork. There are now factories with more computers than workers.

Corks are gauged by a dozen lasers and checked for flaws by electronic cameras before being hermetically packed in sulphur dioxide to prevent mustiness.

A German researcher has developed a process that essentially microwaves corks to kill internal moulds and a firm called Italcork claims its new cork-washing procedure results in a 99.9 percent taint-free product.

In the fields, great care is now taken to cut off the lower part of the bark, a source of contamination by fungi and parasites that can taint the wine.

The Cork Wars

There is a non-violent, but nonetheless voracious war raging between proponents of ‘cork’ and ‘plastic’ wine stoppers. Environmentalists, backed by cork farmers and the government of Portugal, have claimed that cork farming is a sustainable industry in which the ‘art’ is passed down from generation to generation, something that would be threatened if plastic takes over.

They also state that, in many cases, wine taint, which is still not fully understood, is far too readily blamed on the cork farmers and that it is no coincidence that the US plastics industry is pushing hard for the replacement of cork as the US is the prime producer of plastic stoppers.

The multi-million-dollar industry leader is a Seattle-based private firm called Supremecorq, which is rumoured to have Microsoft monopolist Bill Gates as its star investor.

A consortium of California wine makers is backing Neocork, a plastic cork research and development group headed up by the Dow Chemical Company, makers of Agent Orange, pesticides and PVC plastics. Neocork expanded into Europe in 2004, building a (plastic) cork printing and finishing facility in Austria.

On the other side of the coin are claims by the pro-plastic lobby that this is all just ‘disinformation’ put out by greedy cork manufacturers who have brought about the present situation upon themselves.

They say that the problems are being caused by the over-stripping of cork trees and the indiscriminate use of pesticides and chemicals at all stages of farming and production, especially during the 1960’s and 1970’s.

The biggest ‘coup’ for the plastics industry was almost certainly the decision of Marks and Spencer and Safeways to instigate their natural cork ‘ban’ in the UK.

There are wine producers all over the world who are now using plastic corks, even for some of their ‘vintage’ wines. Whatever the truth, and both sides appear to have been guilty of ‘mis’ or ‘dis’ information in their efforts to win, the war will rage on for quite some time to come.

The Pros and Cons

Some (polite) things to do with that pulled cork

1. Take it fishing! It can be used as an impromptu float, bite indicator, holder for hooks so you don’t stab yourself.. and probably numerous other things.
2. Use it as a pin-cushion.
3. Use it as a door-stopper.
4. Put it on the end of sticks and canes in the garden. How many people manage to injure themselves because they don’t see the sticks once they have put them in?
5. Have fun with the kids by making things like boats, animals, mobiles etc.
6. Burnt cork is great (and cheap) make-up for Carnival, Halloween etc.
7. Use it to make old razor blades, Stanley knife blades etc safe by pushing them into the cork before disposing of them in the rubbish bin.
8. Make a cork mosaic.
9. Hang them from your hat, like a real Oz, to keep the flies away! Bear in mind, though, that if you are not actually an Australian or in Australia, you will more than likely just be labeled a ‘prat in a hat’.

One final thought: if you are a regular wine drinker, and given that one bottle in twenty now has a plastic cork, have you ever spotted one? And does it really matter as long as the wine tastes OK? After all, the ‘box of wine’ has been around for a long time.