Pure Expanded Agglomerate
Expanded agglomerate, also known as black agglomerate, is made by means of the agglutination of virgin cork granules, mostly from the pruning of oak trees, with a higher concentration of extractives than other types of cork, which act as a natural adhesive. It is achieved with an industrial process without the use of additives and it is 100% natural.
Granulation: The cork is submitted to a grinding process similar to that for composite agglomerates. The final granule size obtained depends on their intended use, from 3 to 10 mm for acoustic agglomerate and 5 to 22 mm for thermal agglomerate.
Cleaning: Next, impurities are removed, specifically wood and bark pocket, with the aid of densimetric separators and sometimes pneumatic separators or rotating drums. The granulate is stored and dried until the ideal moisture level is reached.
Agglomeration: The granules are placed in autoclaves and, by using steam from water overheated to 300-370 ºC, they undergo expansion and exude their resin (suberin), driving agglomeration without using any foreign additives. Boiling time varies from 17 to 30 minutes, depending on the initial moisture content.
Finishing: The result are expanded cork blocks which, after stabilisation, are rectified and cut into sheets of varying thickness, normally using a bandsaw, after which they are adjusted for size and squareness using a circular saw. The blocks are packaged and stored.