Cork sheet

Overview

Cork is the phellem layer of bark tissue harvested primarily from Quercus suber, the cork oak, native to southwest Europe and northwest Africa, according to Wikipedia. It is composed of suberin, a hydrophobic substance, and is described as impermeable, buoyant, elastic and fire retardant. Cork sheets and corkboard are made from granulated or natural cork, and Wikipedia says sheets are used for bulletin boards and floor and wall tiles. In the shop it is a soft, grippy, vibration-damping sheet rather than a structural panel.

Pros

• Renewable bark: the tree is not cut down to obtain cork; only the bark is stripped and the tree continues to live (Wikipedia).
• Elastic with near-zero Poisson's ratio, so it does not bulge when squeezed (Wikipedia).
• Fire retardant and suited to acoustic and thermal insulation (Wikipedia).
• Low density suits fishing floats and buoys; slipmats use cork because it does not attract dust and dampens static and vibration (Wikipedia).
• Easy to cut with a knife or saw.

Cons

• Not structural. It has no practical stiffness for load-bearing parts.
• Soft surface that dents and tears.
• Wikipedia notes cork can be varnished for flooring, which implies a finish is needed for wear.
• No verified price from sources I opened.
• Screws and fasteners hold poorly; glue it down.

Variants and subspecies

• Corkboard (insulation): a by-product of stopper production, used as a non-allergenic, easy-to-handle alternative to petrochemical insulation (Wikipedia).
• Cork sheets: bulletin boards and wall and floor tiles (Wikipedia). Clever Brand lists 24 x 36 in sheets.
• Cork-cement composites: density 400 to 1500 kg/m3 per Wikipedia.
• Agglomerated cork: Wikipedia says cork from the Chinese cork oak is considered inferior to Q. suber and is used for agglomerated products.

Working and finishing

Cut with a sharp knife or fine saw, and sand lightly. Bond with contact cement or a suitable adhesive to a flat substrate such as MDF (medium-density fibreboard) or Particleboard. Seal with a clear finish if it will be handled or wet.

Staining and finishing colour

Cork is normally left natural; its colour ranges from tan to brown. A clear sealer deepens it. I did not find a source on staining it.

Sustainability and handling

Wikipedia states that cork production is generally considered sustainable because the tree is not felled, that cork products are easy to recycle, and that cork oak forests prevent desertification and shelter endangered species. Stripping occurs about every nine years once trees are about 25 years old, and trees live about 300 years. The montado of Portugal produces about half of the world's cork. Check the origin for FSC or similar certification if it matters to you.

Popular projects

Bulletin boards, wall and floor tiles, slipmats, gaskets, drawer liners and insulation.

Buying notes

Clever Brand lists 24 x 36 in sheets; I could not read a price from the page. Compare sheet thickness and density, and buy from a supplier that publishes both. Corkboard insulation is a separate product from craft sheets.