USES FOR SCRAP CORK

Once the bottle stoppers have been punched out of the cork slabs, there is some leftover cork scrap. This scrap is ground up, molded into large blocks and baked in ovens to make other cork products, such as cork tile flooring and cork message boards.

Cork has been used as bottle stoppers for more than 400 years. It is possibly the best suited material to use as a bottle stopper because it contains a natural waxy substance, called suberin. This substance makes cork impermeable to liquids and gas, and prevents the cork from rotting.

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

Wine corks can be made of either a single piece of cork, or composed of particles, as in champagne corks; corks made of granular particles are called "agglomerated corks".

Natural cork closures are used for about 80% of the 20 billion bottles of wine produced each year. After a decline in use as wine-stoppers due to the increase in the use of cheaper synthetic alternatives, cork wine-stoppers are making a comeback and currently represent approximately 60% of wine-stoppers today.

High-speed flash image of a champagne bottle being uncorked

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. However, unavoidable natural flaws, channels, and cracks in the bark make the cork itself highly inconsistent. In a 2005 closure study, 45% of corks showed gas leakage during pressure testing both from the sides of the cork as well as through the cork body itself.

Since the mid-1990s, a number of wine brands have switched to alternative wine closures such as synthetic plastic stoppers, screw caps, or other closures. In some countries, screw caps are often seen as a cheap alternative destined only for the low grade wines; however, in Australia, for example, much of the non-sparkling wine production now uses these caps as a cork alternative, although some have recently switched back to cork citing issues using screw caps. These alternatives to real cork have both advantageous and controversial properties. For example, while screw tops are generally considered to offer a trichloroanisole (TCA) free seal, it is possible to find TCA contamination in a screw cap bottle.  Additionally, they reduce the oxygen transfer rate to almost zero, which can lead to reductive qualities in the wine. TCA is one of the primary causes of cork taint in wine. However, in recent years major cork producers (Amorim, Álvaro Coelho & Irmãos, Ganau, Cork Supply Group, and Oeneo) have developed methods that remove most TCA from natural wine corks. Natural cork stoppers are important because they allow oxygen to interact with wine for proper aging, and are best suited for wines purchased with the intent to age. Stoppers which resemble natural cork very closely can be made by isolating the suberin component of the cork from the undesirable lignin, mixing it with the same substance used for contact lenses and an adhesive, and molding it into a standardized product, free of TCA or other undesirable substances.

The study "Analysis of the life cycle of Cork, Aluminum and Plastic Wine Closures," commissioned by cork manufacturer Amorim and made public in December 2008, concluded that cork is the most environmentally responsible stopper, in a one-year life cycle analysis comparison with plastic stoppers and aluminum screw caps.