Short Story of Wine Closures
Cork stoppers, made from the bark of the cork tree, has been in use since the time of the ancient Egyptians, where they were used to seal amphorae. An amphora is a vessel, usually a large pottery container, with two handles. Evidence suggests that amphorae were widely used in classical antiquity from the ancient Greeks and Romans to the Celts.
In medieval times, barrels were sealed using wooden stoppers, often with cloth between the barrel and the stopper to provide a better seal. Pitch and wax were also used to provide extra protection. With the advent of glass bottles during the 17th Century, glass stoppers were developed, individually shaped to fit the bottle and tied with thread. A far less expensive stopper, made from cork, soon regained popularity, although this time it required the invention of the corkscrew to help unseal the bottle. Modern closures, using a range of substances and techniques have all been developed with the aim of providing a consistently reliable, easily removable, low cost seal.
What is a Wine Closure?
A stopper or closure on a wine container is necessary to prevent the wine from coming into harmful contact with oxygen. A corked wine is the result of using a cork that has been affected by the action of mold combined with traces of chloride compounds from the environment. Cork taint manifests itself as a smell of a musty cellar, wet carpet or a wet towel, generally not a pleasant aroma.
Cork trees, a species of oak, live on average for 170 years. From the age of 25 years, the cork bark can be stripped or 'harvested' every nine years. The strips are then boiled to kill off any contaminants and corks are punched out at right angles. Corks are then hygienically treated, graded, branded and often coated with a substance to aid extraction (such as paraffin or silicon) before use.
Made from natural cork, ProCork has a permeable (porous) membrane applied to each end of the cork. This reduces the amount of chemicals entering the wine and regulating the way oxygen passes through the cork.
Corks made from synthetic substances, usually a polymer derivative, provide an alternative bottle closure free from the problems of breakage and crumbling. Synthetic corks are manufactured to achieve a consistent cell structure, which reduces the risk of leakage whichever way the bottle is stored.
The screw cap closure has been around in the Australian wine industry since the mid-1970s. It provides a perfect, inert seal. The external part of the cap is made of non-corroding metal, usually an alloy of aluminum. The screw cap liner is made up of expanded polyethylene, tin (to stop oxygen) and PVDC to provide an inert seal with the wine. The closure is corrosion-resistant. To remove the cap, small metal bridges must be broken to separate the top part of the cap and the lower skirt, which remains on the bottle. The bottle can be re-sealed by screwing the cap back on to the bottle. The broken seal indicates that the bottle has been opened, thus providing a tamper proof feature.
Stelvin is a brand name of the most popular screw cap and has become the generic term within the wine industry for all brands of screw cap.