John Coyle, age 9, of Pittsburgh, Pa., for his question:

WHERE DO THEY GET CORK?

Maybe you thought that spongy cork is a kind of plastic material. Not at all. The ancient Romans used the lightweight material to make sandals and also for floats to hold up their fishing nets more than 2,000 years ago, ages before modern plastics were invented. Cork actually comes from an evergreen oak tree that thrives in Spain and Portugal.

A cork tree is an old timer, perhaps as old as 400. At the age of about 10, it begins to grow a thick layer of dry spongy cork around its trunk and branches. This is its special bark. It is cut and peeled away very carefully. Then it is sliced and shaped to make bottle stoppers, soles for shoes and  dozens of other things.  Since the sturdy trees grow slowly, the next harvest of cork barkis not ready for another 10 years.