Wine Corks

Natural cork, with its superior sealing properties, replaced wooden stoppers and waxed rags in wine bottles over 400 years ago.  Although some wine makers are turning to synthetic stoppers and screwcaps for safety and cost concerns, natural cork is still the choice for most.  Lightweight and near-impermeable to liquids and gases, cork is also easy to compress into bottle necks where it expands to form a tight seal, keeping valuable wine inside and damaging oxygen outside.

Cork comes from the thick outer bark of the cork oak tree which grows in Portugal and parts of Spain.  Over 50% of the world’s oak comes from Portugal and about 26% comes from Spain.  The cork oak tree must be at least 25 years old before initial harvesting can begin.  Removing the bark doesn’t damage the tree; more bark grows to replace it.  Re-harvesting can occur about every 12 years.

The bark is harvested with a specially designed axe with a broad blade.  Large rectangular sections are sliced down to the tree’s cambium layer of the trunck and larger branches.  The sections are then gently pulled away to avoid damage to the tree’s inner layers.  The slabs are then boiled in water for an hour or more.  Boiling flattens the slabs and expands the cork cells by as much as 20% into a more pliable honey-comb structure.  The rough outer section of the bark is stripped away and the slabs rest and mature for about three weeks.

The resulting cork planks are then sliced into long, thin sections.  Sharp circular cutters punch out round cork shapes.  These stoppers are then graded by quality.  The best have tight grains, small pores and no cracks.  These are then washed and disinfected with a mild hydrogen peroxide solution.  Corks are then branded or printed with logos before being shipped to wineries.

Now, you know!