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What Are Cork Cells?

Cork cells are microscopic holes in wood that fuel a $1.3 billion per year, multi-national, sustainable industry, providing jobs for approximately thirty thousand people in the United States, Spain, France, Italy, Portugal, and Northern Africa.

Who Discovered Cork Cells?

Robert C. Hooke, of the Royal Society for Scientists, was fascinated with micro-optics. In 1665 Hooke developed a microscope with fifty times magnification, which he used to examine everything he could fit under the lens.

He was examining a sample of cork when he noticed a pattern of irregularly shaped pores. He called them “cells”, after the tiny quarters he had seen in monasteries. The first cellular structures recognized by man, cork cells facilitated the origin of cellular biology.

Popping the Cork

The individual cork cell is made of a waxy substance called suberin that makes it impermeable to water or gases. The roughly fourteen sided cell may be filled with fatty acids, tannins, lignin, or air.

The walls, or lenticels separate and seal the cells into radial rows, that are found in the spongy outer bark of Quercus Suber, or the Cork Oak. The outer layer, or cambium, is made of dead cells that are no longer vital to the tree’s growth.

Once the tree is about twenty years old, it is mature enough to harvest cork. The cambium regenerates every five to ten years, producing an inch or two of dead cells. These may be peeled off in sheets without damaging the tree. The Cork Oak may produce for up to one hundred fifty years.

Put a Cork In It

Cork is one of nature’s wonders. Cork cells are highly resilient, offering a cushioning effect. They are fire retardant, buoyant, insect resistant, and rot resistant. Cork insulates against temperature and sound, and does not collect dust or moisture. When cut, the cells behave as little suction cups providing a non-slip surface.

Cork is found in flooring, roofing, wall coverings, shoes, bulletin boards, gaskets, safety helmets, and golf balls. It is best known for its use as bottle stoppers.

Boffle corks for bottles are cut directly from the sheets of cambium after a brief steam process. The leftover cork is ground into chunks, superheated by steam to reactivate the natural resins, and pressed into forms for all kinds of products. Sometimes synthetic resins are added. This is called agglomerated cork.

Corking it up

Cork is good for the environment. Cork forests grow without the need for irrigation, pesticides, or pruning. The only maintenance required is the excavation of the bark every nine or ten years, which does not harm the tree.

Synthetic products have tried to replace the natural cork. They are cheaper to produce but create up to seventy times the overall carbon emissions of natural cork production.

Fuel used in the manufacturing process of natural cork is typically cork dust; the by product of manufacturing. There is no waste, leaving those cork cells with a very small carbon footprint.