Printing and Finishing - The Graphic Design: Reference and Specification - page 142

Holography: Holographic or three-dimensional imagery is created by digitizing an image
so that it is divided into several layers. The process involves bouncing laser beams off
of mirrors and focusing them onto a photosensitive plate. The holographic design is then
embossed onto coated white paper that is metallized for a shimmery effect. Holography
requires working closely with specialized vendors over a period of several weeks, and
set-up charges can make the process cost prohibitive for small-run projects. Holography
is used on credit cards, trading cards, book covers, beverage packaging, and other
situations where high-volume makes it a cost-effective option.

Lenticular printing: The process creates an animated effect where images flip back and
forth when viewed from different angles. (For instance, a photograph of an individual with
an eye that actually winks). It is achieved by laminating a plastic lens over two or more
images that have been digitized and broken down into a series of dots. Producing a len-
ticular image requires working closely with a lenticular vendor to produce digital imagery
that meets their requirements. The expense and time involved make lenticular printing
suitable for mass-production situations such as product manufacture and packaging but
unrealistic for small-run or short-turnaround projects.

t r a p p i n g to l e r a n c e s
Keeping colors in register means aligning them on press exactly as they have been speci-
fied. But when two colors are adjoining, there is always the possibility that a colorless
gap may occur between the colors if registration isn't exact. To compensate for this, a
slight overlap, called a trap, is created between the two colors. The amount of trapping
will vary, depending on the absorbency of the paper or substrate and printing method
used. Although most commercial printers take responsibility for creating traps, it's useful
to know how trapping tolerances can vary for different printing methods. The following
chart shows typical trapping tolerances for a variety of printing processes and substrates:

Printing Method Substrate Trap (inches) Trap (mm) Trap (pt.)

Sheetfed offset uncoated paper 0.003 0.08 0.25

Sheetfed offset coated paper 0.003 0.08 0.25

Web offset coated paper 0.004 0.10 0.30

Web offset uncoated paper 0.005 0.14 0.40

Web offset newsprint paper 0.006 0.15 0.45

Gravure coated paper 0.003 0.08 0.25

Flexography coated paper 0.006 0.15 0.45

Flexography newsprint paper 0.008 0.20 0.60

Flexography kraft/corrugated paper 0.010 0.25 0.75

Screen printing fabric 0 0 0

Screen printing paper 0.006 0.15 0.45