Cork: Harvesting and processing the bark of cork oaks
Cork harvesting is the process of peeling the outer bark of cork oak trees. The best time to harvest is from May to August, when the bark is growing most rapidly.
The quality of the cork bark reaches a sufficient level only from the third harvest, which is why this cork is called “Amadia”. Experienced professionals can perform the peeling of the tree without permanent damage, because the first layer of reproductive cork naturally connects to the undamaged part of the tree, which is still growing. The regulation of the conditions for harvesting cork oak bark is established by law in order to maintain the health of the trees.
Peeling Cork Bark: A Traditional and Effective Method
The delicate operation of peeling cork has been carried out in the same way for decades. Even today, peeling with a special axe remains the fastest and cleanest method.
- First, the deepest crack in the bark is selected and a vertical cut is made into it, while the tip of the axe is twisted to separate the top layer of bark from the bottom.
- The axe blade is then inserted between the torn strip and the lower layer of bark and the piece is peeled off. The axe is twisted between the trunk and the cork to separate it from the trunk in as large slices as possible.
- A horizontal cut is then made with a dividing line between the cork that is to remain on the tree and the one that is to be removed.
- The bark is then completely stripped from the tree, taking care not to tear it. The larger the pieces that are peeled off, the higher the selling price. The size of the pieces peeled off depends on the skill and experience of the pickers. After the first sheet is removed, the whole process is repeated around the entire trunk.
After harvest: Stabilization and processing for quality products
After harvesting, the cork sheets are allowed to stabilize to achieve the desired quality and can be used for various purposes, such as natural bottle stoppers, discs or pressed cork products. The sheets are stacked and exposed to outdoor conditions for a minimum of six months, where sun, wind and rain help to remove the tar and oxidize the polyphenols, stabilizing the cork texture.
The stabilized cork is then boiled in water for at least one hour. This process is important for increasing the volume of the cork and expanding the pores. It eliminates internal microflora.
After boiling, the cork is left to dry and then stored for three weeks at a precisely controlled temperature and humidity. The edges of the cork boards are then trimmed to create rectangular boards. These boards are further sorted by thickness and quality, taking into account their porosity and any imperfections.
Cork stopper production: Extrusion, inspection and quality classification
After three weeks, the cork boards are cut into strips, which are used to punch out the corks. Regularly shaped boards are suitable for automated machine punching, while less regular strips are punched out by hand. After punching, the ends of each raw cork are cut and smoothed into the correct shape. Suitable offcuts are also used and processed into pressed cork. Corks made from pressed cork are processed with the same care and precision as natural cork. Even unused pieces of cork oak bark are used, for example, to produce insulation and building materials. Every piece of cork oak bark has its own use.
The corks are then scanned to detect any imperfections that could compromise the quality of the liquid in the bottle. The scanning is carried out by automatic optical devices that recognize the structures. Alternatively, manual inspection is carried out by experienced personnel who carefully examine each cork and assign a rating based on their own discretion. The corks are then divided into groups according to their quality.
