Larry Jackson, age 10, of Helena, Mont., for his question:
WHERE DO CORK TREES GROW?
Cork is a lightweight, spongy substance obtained from the bark of the cork oak tree. The tree is a live oak tree that stays green the year around and can be found growing abundantly in Portugal and Spain, where most of the world's cork is produced.
Algeria is the third most important country in cork production.
In addition, the cork oak has been planted in parts of California and in some of the southeastern states, but the total yield of cork there is small.
Cork trees live from 300 to 400 years, but they seldom grow more than 50 feet high. A cork oak must 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.
A cork stripper uses a long handled hatchet to cut oblong sections of bark from the top of the lowest branches to the bottom of the tree. The sections of bark are pried off carefully with the wedge shaped handle of the hatchet.
The inner layer, called the peridem, continues to produce more cork after each stripping. Cork will never grow again on a spot where the inner layer of bark has been bruised by the stripper's hatchet.
The slabs of stripped cork are boiled and a rough, gritty outer layer is scraped off. The boiling dissolves tannic acid from the 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.
Cork is used for insulation. For this purpose, sometimes it is ground and pressed into boards and pipe coverings. Cork insulation is used around freezing pipes of thousands of cold storage plants, meat packing factories, ice cream plants and oil refineries.
Since cork floats in water, it is used in making buoys and floats for fishing nets.
Linoleum is made by mixing cork powder with linseed oil and spreading this paste over canvas or burlap.
Floor, walls and ceilings are made soundproof with corkboard. One of the principal uses for cork is in bottle stoppers, which are called, quite properly, "corks." Thin cork gaskets seat metal bottle caps.
In addition, cork is used in waterproof coatings, in balloon fabric, as filling for automobile tires and as wadding for shotgun cartridges.