Why cork uniqueness?
The uniqueness of cork derives from its structure of air-filled cells, each of which consists of a watertight, flexible compartment. En masse these cells constitute a remarkably effective insulating medium that is also impervious to liquids. Because of its internal matrix of air pockets, cork is also among the lighter natural substances in weight, being only one-fifth as heavy as water. Specialized plastics and other artificial substances have supplanted cork in a number of its former uses, but cork has retained its traditional importance as a stopper for bottles of wine and other alcoholic beverages.
Cork is composed of dead cells that accumulate on the outer surface of the cork oak tree. Because of its honeycomb-like structure, cork consists largely of empty space; its density (weight per unit volume) is one-fourth that of water. Unlike a honeycomb, however, cork consists of irregularly shaped and spaced cells having an average of 14 sides. With 625 millions of these empty cells per cubic inch (40 million per cubic centimeter).
cork is like many layers of microscopic Bubble Wrap, making it an effective cushioning material. Its low density makes cork useful in products like life preservers and buoys. The large amount of dead-air space makes cork an effective insulation material for both temperature and noise. Furthermore, it is fire retardant; flames will only char the surface, and no toxic fumes are generated.
Cutting the surface of cork turns many of the microscopic cells into tiny suction cups, creating an effective non-slip surface. In addition to being flexible, cork is highly resilient. After being crushed under a pressure of 14,000 lbs/in 2 (96,000 kPa), cork will regain 90% of its original size in 24 hours. Cork absorbs neither dust nor moisture, and it resists both rot and insects. Highly resistant to wear, it is used for polishing diamonds.