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Cork is an amazing and versatile material made by nature. Its unique properties have been known for centuries and many practical applications have been discovered. It is comprised of mature dead cells from the cork oat plant. It is cork’s unique cell structure and composition that makes it so remarkable.

Why is Cork Waterproof?

First of all, a mature cork cell is not a living entity. Cork is make up of mature dead cells formed by cork oak (Quercus suber). These dead cells will not die, dry up, shrink or decompose as live plant material would.

Second, the membranes that make up the walls of cork cells have a special compound called suberin. Suberin is a waxy and somewhat rubbery substance that makes the cell walls waterproof.

If you rub a cork bottle stopper between your fingers, you can sense the suberin. This substance is not just on the outside of the stopper, it is part of every cell wall throughout the entire cork material.

Why Does Cork Float in Water?

Anything that has less density than water will float. Cork is about 89% air. This air is trapped inside its cells. The cell walls are so strong, flexible and water-proof, they will not let the air out or water in. Therefore, cork is more dense than the atmosphere but less dense than the water it floats on.

We have all seen bottle stoppers and bulletin boards made of cork but few of us realize how unique and remarkable this naturally-made material really is. Cork can be pricey because it cannot be manufactured by man in an unlimited quantity. Through careful cultivation, we will have cork production for centuries to come.

What is the Most Popular Use of Cork?

Cork is ideal as a bottle stopper for products such as wine. After the wine maker compresses the cork bottle stopper and places it into the neck of the bottle, the cork expands, trying to reach its original size. This causes the stopper to make and keep a very tight seal, even after years or decades of being compressed into the neck of a bottle.

It is challenging to place a cork stopper back into the neck of a bottle once it has been removed. The air in the cells of the cork want to remain at normal air pressure. The cell walls want to stay at their neutral positions. Wine makers need and use a special tool for putting cork stoppers into their bottles.

What are Some Other Uses of Cork?

  • Insulation

Cork cells make excellent insulation. The air pockets inside the cells are not a good conductor or heat or cold. Heat or cold on one side of a sheet of cork will not easily pass through to the other side. Common applications that use cork’s insulation property are hot pads and flooring. However, if the cork has been ground up and the cell walls are broken, there are no pockets of air. Cork particles in this condition, which are merely broken cell walls, do not make a good insulation but have been used for garden mulch.

  • Seals and Gaskets

The combination of the cork’s property to struggle to retain its original shape and the waterproof suberin in the cell walls make cork an excellent choice for jar seals or engine gaskets. Since cork won’t shrink or decompose, it is a long-lasting and dependable material to use for applications that must not fail.

  • Drink Coasters, Fishing Rod Handles and Tennis Racket Handles

These applications take advantage of cork’s waterproof property. Water droplets from a sweating glass will not penetrate the sheet of c.ork to the table below. Water on an angler’s or tennis player’s hands will not ruin the handles of their rod or racket because of the suberin in the c.ork walls. Furthermore, if the angler drops his fishing rod into the water, the cork in the handle will help the rod to float, making it easier to recover.