Lori Miale, age 10, of San Diego, California, for her question:

What chemicals are used to make fiber glass?

This marvelous material may be a silken drapery or a fishing rod or the hard top on the family auto. When you see and handle these man made fiber glass wonders, you would never guess that the main ingredient is a rather special sort of sand. The most suitable sand is one that contains a lot of a tough, gritty material called silica. The same sort of silica sand is the main ingredient used to make ordinary glass. The other main ingredients in both glass and fiber glass are soda and lime.

The recipe begins when the chemical ingredients are melted together in a seething furnace. The glassy mixture may be molded into lovely little marbles, about five¬eighths of an inch wide. This gives a sharp eyed expert a chance to check each glassy ball for possible impurities. Then the marbles are re melted. The hot glass flows through holes in a spinning drum. It comes through as fibrous threads of fiber glass, which may be finer than human hair. The glass in one little marble can be stretched to make more than 90 miles of the finest fiber glass thread.