Kelli Farlow, age 13, of Rome, N.Y., for her question.
WHERE DO WE FIND CORK?
Cork is obtained from the bark of the cork oak tree. Most of the world's cork is produced from trees that grow in Portugal and Spain. Algeria is the third most important country in cork production.
People have been using cork since 400 B.C. The Romans made sandals of cork and also used the material to float anchors and fish nets. Cork bottle stoppers came along about 1600.
The cork tree is a live oak. It is green the year around.
The outer layer of the bark is composed of dead cells whose thin walls have become thickened and waxy. These cells are so compact that each may be in contact with 14 others.
The cork tree lives from 300 to 400 years. It seldom grows to be more than 50 feet high.
A cork tree has to be about 20 years old before its bark is thick enough to be stripped. The first layer removed is called the virgin bark. Workers strip the bark in June, July and August. Each tree can be stripped about once every eight to 10 years. The best cork comes after the second stripping.
Long, oblong sections of bark are cut from the top of the lowest branches to the bottom of the tree by a cork stripper who uses a long handled hatchet. The sections of bark are pried off carefully with the wedge shaped handle of the hatchet.
The inner layer, called the periderm, continues to produce more cork after each stripping. Cork will never grow again on a spot where the inner layer of the bark has been bruised by the stripper's hatchet, so great care must be exercised by the stripper.
Slabs of stripped cork are boiled and a rough, gritty outer layer is scraped off. The boiling dissolves tannic acid from cork and softens the material so that the slabs can be straightened out and packed in bundles.
Before being loaded on ships, cork is sorted according to quality and thickness.
Most cork today is used for insulation. For this purpose, it is ground and pressed into boards and pipe coverings. In this form, cork covers the walls and freezing pipes of thousands of cold storage plants, meatpacking factories, ice cream plants and oil refineries.
Cork is also used in making buoys and floats for fishing nets. It floats in water and is ideal for this use.
Some linoleum is made by mixing cork powder with linseed oil and spreading this paste over canvas or burlap. Also, some floors, walls and ceilings are made soundproof with corkboard.
One of the principal uses of the material is for bottle stoppers. Thin cork gaskets are also used to seal metal bottle caps.
Cork is also used in waterproof coatings, in balloon fabric, as filling for automobile tires and as wadding for shotgun cartridges. Cork shavings, in addition, are burned to make "cork black" paint for artists.