Happy Rubber Eraser Day!

Suppose Henry Ford had built his first automobile in 1896, but brakes weren't going to be invented for another 100 years. It sounds silly, doesn't it? But that's sort of what happened with pencils and erasers.

People had been writing with what we would call a pencil (with a graphite "lead") since about the mid-1500s. But it was 1770 before anyone could erase.

That's when English chemist Joseph Priestly found that a small cube of latex, or rubber, literally "rubbed" out pencil marks. Latex comes from rubber trees, which then grew only in the New World. Priestly - better known for discovering oxygen - named it the "rubber eraser."

It took almost another 100 years before anyone thought to put erasers on pencils. Hyman Lipman of Philadelphia patented the idea in 1858. Today, most wooden pencils sold in the United States have erasers. (In Europe, though, most pencils still do not.)

Erasers are everywhere - from the "plugs" at the end of pencils to gray gum erasers for artists and oblong pink ones. Now erasers even have their own day, thanks to Dorothy Dudley Muth of Redwood, Calif. She wrote to "Chase's Calendar of Events" four years ago. The 750-page annual lists anniversaries and celebrated days. Chase's now lists today as "Rubber Eraser Day" in the US. The date is also the deadline for filing federal income taxes - an activity in which erasers often are put to good use.

When you use a "rubber" eraser today, you're not using real rubber. According to Matthew Filion, a chemical engineer at an eraser plant for Dixon-Ticonderoga pencils in Acton-Vale, Quebec, erasers are synthetic now. They used to be made of natural rubber, dye, and water. But for 50 years they have been made of synthetic rubber, pumice (a volcanic rock), clay or calcium (fillers), color, and oil. Some erasers are made of vinyl (plastic), which erases better.

Two final questions: Why are so many erasers pink? And what do you call the crumbs of eraser you must brush off the page after erasing? Erasers don't have to be pink, Mr. Filion says. Someone started making them pink and it caught on. And the little bits of eraser? Filion calls them "trailings."

* For more information, try this Web site: www.pencils.com