The cover of a book is often composed of
uniform color blocks of different colors or regular gradual color blocks and
text, which can be made by overprint of four primary colors or by blending of
monochromatic ink, and then printing only one particular type of monochromatic
ink at the same color block. For book printing, in combination with
the consideration of improving printing quality and saving overprint times,
spot-color printing is sometimes used.
Four-color printing: Photographs taken by
color photography reflecting the rich and varied colors of nature, a painter's
work of color or other pictures containing many different colors, must be
scanned by an electronic color separation machine or a color desktop system for
reproduction for technical or economic reasons.
The angle of product quality:
when printing large area light color uniform color block, usually use in the
original ink to add medium light agent to mix the spot color ink, and then
carry on the field printing, so that the ink layer is thicker, it is easier to
get the color uniform and thick effect. If a four-color printing process is
adopted in book printing, a low number
of flat mesh points must be used. But the low number of flat mesh dot in the
sun plate is easy by the small sand or slightly bad exhaust caused by a few
parts of the dot smaller, resulting in uneven ink. Printing is easy due to too
much water layout, paper powder in the printing plate and blanket accumulation,
paper smoothness and other reasons resulting in small dot ink transfer. Thus
appears the ink color to become shallow and the ink color uneven.
The angle of economic benefit: mainly consider
whether the technology of using spot color printing can save overprint times in book printing. Because reducing
the number of overprint can save both printing costs and pre-print production
costs.