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Cork is a material that finds more and more applications. You have seen wine corks. It is also used to make flooring and even yoga mats. It is considered a durable, environmentally friendly, and non-toxic material.
It is also probably the most sustainably harvested material because it is re-harvested from the same tree every 9 years and trees live up to 300 years!
Have you wondered how it is made?
- Using a specially designed hatchet, the harvester slices through the cork layer on the trunk of the tree, taking care not to cut deep enough to damage the living portion of the trunk. Horizontal cuts are made at the base of the trunk and just below the lowest branches. A few vertical cuts separate the circumferential cork ring into sections of an appropriate size. Using the wedge-shaped handle of the hatchet, the harvester strips each panel of cork from the tree. On some large trees, cork is also stripped from the lower branches.
- The planks are stacked outdoors and left to cure for a time, ranging from a few weeks to six months. The fresh air, sun, and rain encourage chemical changes that improve the quality of the cork. By the end of the curing process, the planks have flattened out and lost about 20% of their original moisture content.
- The planks are then treated with heat and water to remove dirt and water-soluble components like tannin, and to make the cork softer and more flexible. This process typically involves lowering stacks of planks into large copper vats filled with boiling water containing a fungicide. Heavy weights are placed on top of the planks to keep it submerged for 30-75 minutes.
- When the planks are removed from the vat, a hoe-shaped knife is used to scrape off the poor-quality outer layer of cork, which amounts to about 2% of the volume of the plank but 20% of its weight. The planks are stacked in a dark cellar and allowed to dry and cure under controlled humidity for a few more weeks.
- The planks are trimmed to a uniform, rectangular shape and are sorted by quality.
Other than the use of fungicide, it is a pretty environmentally friendly process. If you want to learn what products contains cork, head over here.