In color printing

Color printing

Color printing or Colour printing is the reproduction of an image or text in color...

, registration is the method of correlating overlapping colors on one single image. There are many different styles and types of registration, many of which employ the alignment of specific marks.

Purpose

When printing an image that has more than one color, depending on the method of printing, it is necessary to print the image one separate time for each separate color. Each one is called a "color run," and they can be pulled from the same surface, inked differently, or from a completely different surface. So that the final image is consistent, and so each of the colors lines up correctly, a system of registration is necessary. Different printing devices have different methods of creating separate color runs.

Types of (stone) lithography registration

There are many different styles of registration for many different types of printing. These deal with stone lithography

Lithography

Lithography is a method for printing using a stone or a metal plate with a completely smooth surface...

, as used in fine arts printmaking

Printmaking

Printmaking is the process of making artworks by printing, normally on paper. Printmaking normally covers only the process of creating prints with an element of originality, rather than just being a photographic reproduction of a painting. Except in the case of monotyping, the process is capable...

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T-bar

This method, using small measured registration marks on both the stone and the paper, is very accurate and simple to do. The printer measures the exact size of the paper and the desired margins. Then marks are made at both ends of the sheet of paper, and corresponding marks (usually in the shape of a "T") are made on the stone. Then the printer matches the marks on the paper to those on the stone. This way many runs of different colors can be pulled exactly in line with one another, each of them measured from the same system of marks.

Pin-hole

This method involves laying the paper on the un-inked surface, and making a pin-hole through both the bottom and top of the paper, being careful to make a mark in the stone's surface. Then the locations of the holes are transferred to each sheet of paper to be printed. When printing, one should place pins in each hole of a sheet of paper, and lower it onto the inked stone, placing each pin in its respective hole in the stone. This method can ruin paper by creating holes. And if the holes get too large, they lose their function as registration devices.

Eye-balling

This method relies solely on hand-eye coordination. The printer places the paper over the stone-image, measuring and judging registration by eye. This is not very consistent, depending on the person.