Cork and Cork Trees

Corks for Wine Bottles

There are at least four types, or general categories of wine corks:

• Naturally Cut Corks -- these are corks that are cut directly from harvest cork bark, and rely on the elasticity of the cork to seal the bottle. Typically, these are the highest quality corks (and thus the most expensive). If you plan on storing your wine for longer than a year, than natural corks are suggested.

• Agglomerated Corks -- These corks are created by chipping raw cork into very small pieces, and then gluing them back together to the desired size and shape of the cork. In some ways, these corks are analogous to particle board in the construction industry. Typically, agglomerated corks are less expensive than natural corks. These corks are very cost effective for use in wines that shall be stored for less than one year.
  
  
  

• Synthetic Corks -- Made from synthetic resins, these corks will not dry out or rot. The main disadvantage of synthetic corks is that a super heavy duty corker is needed to insert these corks into bottles. In addition, it is more difficult to extract these corks from a bottle than a traditional corkwood cork.

• Plastic Champagne Corks -- These corks are designed to be used with champagne bottles. Insertion of the cork is performed with the with a hammer. The cork, in conjunction with the champagne bottle is designed to make a very strong seal--to withhold the pressures produced by champagne.
  • Champagne corks and bottles can be used for storing wine. The main advantage is that champagne corks can be re-used for bottling (as corkwood corks can only be used once).

What Size Cork to use

The standard wine bottle has an opening of 18.5 mm. Obviously, the "standard" cork has been designed to fit the standard wine bottle. Cork sizes are designated by a number and length. The number corresponds to the diameter of the cork.

• The #9 cork, is the standard diameter cork for wine bottles. Typical lengths are 1.5 inches, and 1.75 inches. Shorter corks (1.5 inches) are recommended for wines to be aged less than one year. Longer corks (1.75 inches) are recommended for wines to be aged more than one year, as the longer corks will be less prone to dry out.
• The #8 cork is the standard size cork for champagne bottles, and some 375 ml bottles.
• The #7 cork is the standar size cork for beer bottles.

Beveled Corks

Some corks are beveled at one or both ends. A beveled cork allows for easier insertion of the cork into the bottle during the bottling process. Keep in mind that when using beveled corks, the effective length of the cork is offset by the length of the bevel on both ends.

Cork Trees

Traditionally, corks are made from the bark of a the evergreen species of oak genus known as the Quercus. The species is know as suber. Native to southwest Europe and northwest Africa, the cork oak has been introduced into warmer regions of the United States (California). Bark from the cork tree can be cultivated approximately every ten years, and processed as "corks" for wine bottles, or corkwood for other commercial purposes. Harvesting of the cork bark is performed by hand, and does not harm the tree. After harvest, a new layer of cork bark will grow again, and the tree will be ready for harvest again ten years later.

• Cork Oak Trees (Quercus suber) can live for 150-250 years. A single cork tree can be harvested one two two dozen times for cork bark.
• Portugal produces 50% of the worlds cork. It is illegal to cut down a cork tree in Portugal.

For more information on Cork Oaks see:

• USDA Database -- Cork Oak
• Cork Oak-- Harvest Pictures - a cool sight showing picture of cork oak and cork before and & harvest
• Cork Oak -- On CA registry of Big Trees - A huge cork oak!