Types of Printing
Soon after his time in Basel, Dürer took up a new medium–one that would prove very important not only in his own later work but also in shaping the directions that print would subsequently take us. It was copperplate engraving. Copperplate was less in evidence than woodcuts were during the maturation of print [in the fifteenth century]. Yet it came into use at the same time that woodcuts were finding their new popularity. It represented the second of the tree essential forms of printed images, the third being lithography.
Woodcuts are a form of block printing, in which every part of the surface that is to be inked, and which is intended to touch paper, is raised. Copperplate engraving is a form of intaglio. The word intaglio comes from the Latin intagliare, "to cut into," and refers to the process in which an image is cut into a plate. Ink is spread on the plate, filling in the cuts, and the excess is wiped away. The incisions then hold just enough ink to leave their mark on the paper.
Lithography, however, would not be invented until the nineteenth century. It is a process in which a surface (originally of stone) is treated chemically. Ink adheres only where it has a chemical affinity. One inks the plate, then wipes off the excess ink. That leaves just enough ink in the areas where the plate was treated to make an image.
[John H. Lienhard, How Invention Begins : Echoes of Old Voices in the Rise of New Machines (Oxford : Oxford University Press, 2006), pp. 179–180]