The History Behind It All
They Are Everywhere We Go
How It Works
In the first stage of the xerography, the conducting aluminum drum is grounded so that a negative charge is induced under the thin layer of positively charged selenium. In the second stage, the surface of the drum is exposed to the image of what is to be copied. Where the image is light, the selenium becomes conducting, and the positive charge is becomes neutral. In dark areas, the positive charge remains, and so the image transfers to the drum.
The third stage takes dry black powder, called toner, and sprays it with a negative charge so that it will be attracted to the positive areas of the drum. Then, a blank piece of paper is given a greater positive charge than on the drum so that it will pull the toner from the drum.
Finally, the paper and electrostatically hold the toner that is passed through heated pressure rollers, which melt and permanently attach the toner within the fibers of the paper.
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