Originally etching was used to decorate armor in Medieval times. Decorated parts of the armor were filled in to give the designs a contrast.
Etching uses acid to remove metal, whereas engraving does not.
A blank piece of copper is covered in wax, then a design is etched onto the plate through the wax. The plate is then dunked into a tank of acid.
The acid eats away at the exposed copper, which leaves behind textured marks. The plate will then be taken out of the acid and cleaned.
Once the plate is cleaned, an ink will be daubed into the design. It will be wiped off, leaving ink within the grooves.
The plate will be processed through a roller, with a piece of paper applied to the top. This will leave an imprint of the image onto the paper.