Audubon prints. What is a copper plate?

What is a copper plate?

Audubon originals are often referred to by a specific plate number. These large smooth copper plates, numbered from 1 to 435, had reverse images etched into them such as shown here for the Labrador Falcon. The plate was then (1) Black-inked, (2) Dampened paper was pressed upon it. (3) The paper was pulled from the plate, resulting in a properly oriented black and white image. (4) The image was then hand colored. This was repeated about 200 times, after which the plates lost their crisp edge. This is why many original documents and works of art from this time period were limited to about 200 copies.