Cork is made from the bark of a tree, Quercus suber, or the cork oak. These trees can grow pretty big, and they have really thick, rugged bark. One plus side to cork cultivation is that you don’t have to chop down a tree to make corks—you can harvest the bark without harming the tree, and then do it again in about another 10 years.
image credit: Science Channel
Before processing, the cork planks are put on pallets. Then they are ready for the first stage in the cork production process: boiling. The planks are boiled to soften them, and also to clean them. In the bad old days these would be boiled in murky pits without the water being changed very often.via(wineanorak)
The boiled planks are flatter and easier to work with,Next the planks are graded and cut into workable pieces.Some will be used for punching natural corks out of; others will be used to make technical corks. What remains after the corks have been punched.
This remaining cork can be ground up to make granules that can then be glued together to make agglomerate cork.The corks are optically sorted: blasts of air are used to send the corks into the right grade bins.Great care is taken sorting the top grade corks.