Belva Walker, age 12, of Casper, Wyo., for her question:
HOW IS LEAD PUT INTO PENCILS?
Lead pencils actually have no lead in them. The marking material is usually a mixture of mineral graphite and fine clay combined with certain chemicals and wax.
When graphite was first used in pencils, many people thought it contained lead. Therefore, they called it lead or black lead. And that's the reason why we still call the graphic mixture "lead" and the pencils "lead pencils."
There's a real art getting lead into the pencil.
First, workers blend the clay and graphite with water in a high speed mixer. The mixture is placed in a machine and squeezed out of a narrow opening as one lone black string of lead. The lead is cut into pieces about seven and a quarter inches long.
The pieces of lead are then hardened in firing ovens, and finally they are treated with a wax so they will write smoothly.
The wood cases for most pencils are made of incense cedar. This wood has a soft, straight grain that permits easy sharpening without splitting.
Workmen saw the cedar logs into slats that are seven and a quarter inches long, a quarter of an inch thick and two and three quarters of an inch wide. The slats are then heated in an oven to remove all the moisture.
Next the workmen cut nine parallel grooves in each slat. Lead strips are laid in the grooves and another slat is glued on top, making a sort of sandwich.
The pencil sandwich is then dried and cut into nine pieces, each in the shape of a pencil. Workers use machines to sand the pencils until they are smooth.
Next workers apply several coats of paint and varnish to give the pencil a shiny finish. A machine then stamps the pencils with the name of the maker. And another machine cuts a small shoulder or rim at one end where a brass ring called a ferrule is placed and an eraser is clamped into it.
The amount of clay that pencil makers mix with graphite depends on how hard they wish to make the lead. The less clay they use, the softer and blacker the lead will be.
Colored pencils are made in much the same way as lead pencils. They also contain clay and wax, but the clay and wax are mixed with coloring materials called pigments and dyes, rather than with graphite.
Colored leads made from dyes are widely used because their marks can be removed with soap and water.
The word pencil comes from the Latin penicillus, which means little tail or little brush. The earliest writing tools probably were brushes made from plants.
The ancient Greeks and Romans first used pieces of lead as pencils before the birth of Christ. These pencils made faint lines.
The English made the first graphite pencils in the mid 1500s and the Germans were the first to enclose the graphite in a wood case, about 1650.