Wine cork  Wine corks are a stopper used to seal wine bottles. They are typically made from cork (bark of the cork oak), though synthetic materials can be used. Common alternative wine closures include screw caps and glass stoppers. 68 percent of all cork is produced for wine bottle stoppers. Corks are manufactured for still wines as well as sparkling wines; the latter are bottled under pressure, forcing the corks to take on a mushroom shape. They are fastened with a wire cage known as a muselet. 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. The inventor of cork-based wine stoppers is unknown. Colloquial stories attribute the Benedictine monk Dom Pérignon. The stoppers date to about the 1600s. In the early 21st century, the problem of cork taint became prevalent, leading many producers to stop using corks in favor of alternatives. Screw caps became especially prominent in Australia and New Zealand by 2010. Most cork was sourced from around the Mediterranean Basin, far from the Oceanian countries. Following issues with cork taint, the cork industry invested in new techniques and equipment, reducing TCA chemicals in wine by 95 percent. Cork producers began promoting the cork's environmental and economic benefits. Like other cork products, natural wine corks are derived from the bark of cork oak trees. The bark is carefully peeled away and cut into sheets before processing. The oak trees are not cut down, and only about half of its bark is removed at any time. Cork oaks are first harvested at 25 years old, and take place every 9 years. After the third harvest, the bark is of sufficient quality for producing wine corks. Portugal is the largest producer of corks, at 52.5 percent, followed by Spain, Italy, and Algeria. The majority of Portugal's production is in the region of Alentejo, at 72 percent of national production. 68 percent of all cork is produced for wine bottle stoppers. Corks can be made in several ways:   Cork stoppers are moisture-resistant, are slow to deteriorate, they help wine age, and provide a waterproof seal. The stoppers are associated with a perception of high quality wine, especially as cheaper alternatives are common with lower-cost wine. Because of the cellular structure of cork, it is easily compressed upon insertion into a bottle and will expand to form a tight seal.