Plate Division Methods for Book Sections
There are two main methods of printing and binding book sections.
The first method is called turnover plate printing, in which the same plate can be used to print both the front and back sides of a sheet without changing the plate. For example, in a 16mo (16-page) sheet, a 4-page-by-2-form turnover plate layout can be used for printing.
The second method is called overlay plate printing, in which after printing one side of the sheet, all the plates must be changed before printing the other side. An example of this is the 16-page book sections in a 25mo (25-page) sheet.
Depending on the type of book section, the process of dividing plates involves separating from the plates (arranged in page-number order) the front or back pages required for overlay printing. This operation of separating plates is called plate division. Plate division is an important process step before layout (also called imposition or plate assembly).
Plate division can be classified into three main types:
1. Even-numbered section plate division: such as 2-, 4-, 6-, 8-, or 16-page sections.
2. Odd-numbered section plate division: such as 1-, 3-, or 5-page sections.
3. Mixed section plate division: such as long 6-page, long 9-page, or long 10-page sections.
Using a number-line principle to illustrate the rule of plate division, the “principle of plate division” column in the diagram represents how each point on the number line is separated and transferred to either the front (+) or back (–) side of the section, forming the page sequence for each side. The result gives the exact page numbers for each side of the section.
The “principle of plate division” shows the general rule common to all sections of the same type, while the “page sequence decomposition” column specifies the particular arrangement of a given section, clearly showing which pages belong to the front plate and which to the back plate.
The concept of selecting points on the number line and the plate division characteristics of each type of section will be discussed in detail later.
In this text, the surface containing the first and last page numbers of a section (or sheet) is called the front side and is marked with “+”; the opposite side is called the back side and is marked with “–”.
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