(Lansing State Journal, April 28, 1993)
Question submitted by Morgan Halstrum.
There are two main types of copy machines, xerographic and electrostatic. Both use the same process to make a copy but they each do it in a slightly different way.
When you place a page on a copier and press the start button the copier starts by using a series of mirrors and lenses to project an image of the page onto the side of a rotating tube. In a xerographic copier this tube is light sensitive. The picture that is projected onto the tube causes electrostatic charge to collect on the tube in a pattern that matches the page that you are copying. The tube is then coated with a dust called toner which sticks to the charged parts of the tube. A piece of paper is then pressed against the tube and the toner is transferred to the paper. The paper now has a dark image of the original page. This paper is then heated to bake the toner and the copying is done.
This is the same process that an electrostatic copier uses except that instead of a light sensitive tube, light sensitive paper is used. The image is projected directly onto the paper which produces a pattern of charge, is coated with toner and baked to produce a final copy.