Technical cork stoppers
The process of production of technical corks is divided into three distinct stages: production of natural cork disks – which are placed on the ends, manufacture of the agglomerated cork body, and assembly of the cork stopper.
Production of discs
Cork planks used for the production of discs are selected and boiled in a process identical to that for the production of natural cork stoppers. The two sides of the planks (the rougher, the outer part of the tree and the part closest to the trunk) are removed in order to obtain soft, uniform sheets of cork with a thickness of around 6.5 mm.
These sheets are mechanically punched in circles – discs the size of the ends of the stoppers to be manufactured. The discs undergo optical selection in order to sort them into established categories, normally one of 4 quality grades.
For the cleaning of these discs, specialist companies have their own systems based on washing in purified water at a temperature of around 70º, without chlorine. After washing, the discs are dried and stored in silos until they are used.
Production of the body
The bodies of technical stoppers are formed by granules obtained from the by-product of high quality cork products and punching of natural cork stoppers. These by-products are transformed into granules of different sizes by grinding machines. These granules are then agglomerated using food-grade polyurethane glue, and the bodies are either individually moulded or extruded, resulting in rods which are cut in the desired length.
Assembly of the stoppers
The discs and agglomerated bodies are fed into assembly machines via silos. The discs pass in front of cameras which select the side of the disc that will come into contact with the wine. A mark is printed by the machine on the opposite side of the stopper. This mark is detected by a camera in the assembly machine, indicating that this is the side to be glued to the stopper body. The discs are glued to the end of the agglomerated cork cylinder using a glue which is approved for contact with foodstuffs by the FDA (Food and Drug Administration).
The assembled stopper is dried in order to ensure that the glue is completely dry, after which it moves to the polishing or rectification stage. Here, as for natural stoppers, the stoppers are corrected in order to give them the required dimensions. The washing, sorting, finishing (marking) and packaging processes are, from this point, similar to those for natural cork stoppers.