When ordering herbal cork granules (as opposed to expanded cork granules), thickness is the most crucial factor the you will need to consider. Cork granule density can vary between 60 kg/m3 and 220 kg/m3 and also the properties and appearance that the granules along this spectrum will differ enormously. In this article we will look in ~ what thickness of cork granules are obtainable for various usages, but an initial an explanation of why cork granule densities can vary therefore much.

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Cork is produced when the bark is stripped turn off cork oak trees (incidentally, this does no kill the tree and the bark will regenerate in around 9 years as soon as it can be harvest again, do cork among the most environmentally friendly products on the planet!). This cork bark will have actually a soft within layer (where the is nearest the trunk), yet the outside of the bark will be hard, brittle and also woody. This bark is cut into strips and also natural corks are punched out of the softer layer, leaving behind off-cuts which will include both softer cork from in between the punch holes and hard cork from the outside bark.

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Cork gift punched the end of bark strips. Note the darker colour external of the bark at the peak of the photo.
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Here you have the right to see the punched-out cork bark strips, all set for the grinder to do cork granules

These off-cuts are then passed v a grinder , developing granules of assorted sizes and densities. This granules room then sorted by size (using mesh screens) and also densities (using sloped shower tables) to kind a range of options in miscellaneous bands of granules size and density. Therefore for instance we might supply you with cork granules of 1-2mm and also 120-140 kg/m3.

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The cork granules space vibrated on a sloping surface ar to different them through density.

The lower density granules from approximately 60 to 80 kg/m3 room the most prized as they space the most elastic and also are mostly used to do micro-agglomerated alcohol cork stoppers and micro-agglomerated bar-top cork stoppers and blocks the agglomerated cork which deserve to be provided to make cork lids and other agglomerated cork items. Greater density granules cannot be used to make cork stoppers, since they are insufficiently elastic to do a an excellent seal in the bottle, however there space a most uses for higher density granules.

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The biggest use because that mid-density granules (so 90 kg/m3 approximately 180 kg/m3) is cork flooring, yet they are also used significantly for man-made turf cork infill and also for coarse granule insulation boards and also a variety of other usages. As the density gets higher, therefore the cork granules become much more brittle and less elastic, for this reason the cork begins to behave an ext like wood. Due to the fact that there is less need for cork granules the greater the density is, the price additionally decreases significantly with density. So because that the lowest thickness cork granules you have the right to pay end €4 every kg, however for the highest thickness granules, much less than €1 per kg.

The size of cork granule does not generally effect price and also will be created in bands, starting at 0.2-0.5mm and also going as much as 8-12mm. Smaller than this granule dimension is cork flour or dust, i m sorry is produced when cork commodities are ground under to dimension using grind stones, i beg your pardon makes very fine flour of about 200 nanometres in diameter.