Prints in color require two or more blocks, plates, screens or stones, one for each color, printed sequentially on top of each other to produce the final work of art. This process is called registration.
In printmaking processes requiring more than one application of ink or other medium, the problem exists as to how to line up properly areas of an image to receive ink in each application. The most obvious example of this would be a multi-color image in which each color is applied in a separate step. The lining up of the results of each step in a multistep printmaking process is called “registration.” Proper registration results in the various components of an image being in their proper place. But, for artistic reasons, improper registration is not necessarily the ruination of an image.
This can vary considerably from process to process. It generally involves placing the substrate, generally paper, in correct alignment with the printmaking element that will be supplying it with coloration.