The cork oak - Quercus suber - is grown abundantly in Spain. The bark from the tree is stripped off
when the tree is about 20 years old, and then boiled to remove some of the tannin and to make it more flexible.
Cork trees are usually stripped of their bark every 10 years or so, until they are 100 or more years old.
The quality of cork improves with each harvest, the fifth one being perhaps the best.
Cork has been used for more than 2,000 years. In ancient times, it was used for life preservers,
shoe soles, and floats for fishing nets, and was made into stoppers for wine vessels and casks.
When glass bottles came into general use in the 15th century, the cork industry expanded greatly.
Many cork products have been now replaced by rubber and plastic substitutes.