A Portuguese cork oak usually can be stripped for the first time when the tree is over 25 years and its girth reaches 70 centimeters. The producers usually strip the oak bark in the most active month (May to August) of the oak growth, the stripped oak will regenerate naturally, and it will be stripped every 9 years afterwards.

The first stripped cork is called“initial cork”, the cork which is stripped nine years later is called “restriped cork”. The thickness of cork is generally 4 to 5 centimeters, quality cork can reach 8 to 9 centimeters. Each stripping doesn’t damage the oak, on the contrary, it helps the oak tree grow and the bark grow thicker and thicker. Therefore, cork is a perfect natural raw material which can not be reproduced through any industrial or technological process.