Steve Davis, age 9, of Newport News, Virginia, for his question:

How do they make mirrors?

The trick is to make the light bounce back from the shiny surface of the mirror. This is done by coating the back of the glass with layers of special chemicals. These layers must be smoother than smooth, or the light rays will bounce at odd angles and reflect a bumpy image. Backing a mirror takes patience and special skills and every step of the operation is rinsed perfectly clean. The best mirrors are made from perfectly level sheets of thick plate glass, highly polished to reflect back as much light as possible.

Manufacturers use various chemical recipes to coat the backs of their mirrors. To create a quality plate glass mirror, the first coat is a thin, perfectly even layer of silver salts. A layer of copper is spread on top to protect the silver. This ticklish job is done in an electrolytic bath to apply the copper particles.in an even layer. The silver and copper layers then get a coat of lacquer and lastly a sturdy coat of protective paint.