Cork

Cork is a natural material obtained from the bark of the cork oak (Quercus suber). It consists of suberin, a hydrophobic substance, and is composed of millions of microscopic air-filled cells, making it lightweight and compressible.

Description of what it is like

It is a spongy, light, and elastic material with a woody texture but soft to the touch. It floats in water and does not absorb moisture easily.

Origin and where to find it

• Environments: Mediterranean forests (Portugal, Spain, North Africa).
• Signs: Trees with thick, rugged, spongy bark.
• Harvest: The bark is stripped from the living tree without harming it.

Minimum processing required

• Harvesting: Carefully stripping the bark in summer.
• Boiling: To clean it, remove insects, and increase flexibility and volume.
• Drying: To stabilize moisture content.
• Cutting: Into desired shapes (stoppers, boards).

Tools needed to work on it

• Axe/Hatchet: Specialized axes for stripping bark without damaging the cambium.
• Knife: For shaping stoppers or floats.
• Boiling vat: For processing raw bark.

Common forms of use

• Stoppers: Sealing wine or oil bottles due to elasticity and impermeability.
• Boards: Compressed granules for wall or floor insulation.
• Floats: For fishing nets or life preservers.

Possible substitutes

• Rubber/Silicone: For stoppers and gaskets (modern).
• Polystyrene: For insulation and buoyancy (modern).
• Corn cobs: Primitive stoppers (less effective).

Limitations and common failures

• Brittleness: Can crumble if very old or dry.
• Taint: “Cork taint” (TCA) can spoil wine if the cork is infected with fungus.
• Scarcity: Trees take decades to mature and years between harvests.

Risks and safety

• Fire: Although fire-resistant compared to wood, it will eventually burn.
• Dust: Cork dust can be flammable or irritating.

Related materials

• Wood: From the same tree, but different properties.
• Natural Rubber: Another elastic natural material.