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Prepress for Special-Effect Garment Printing

(December 2012) posted on Tue Jan 29, 2013

Decorating garments with special-effect inks can be a daunting task when you don’t have everything in place in prepress. These tips will assist you in building reliable and repeatable processes and procedures.


By Screen Printing's Solution Sourcebook

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Some special effects require that the garments undergo additional processing steps after printing—some of which necessitate the removal of garments from the press before the specialty ink or coating is applied. Caviar beads, flocking, metallic flakes, and large glitter are often applied off-press to printed adhesives or on one of the last print positions on press. Specialized press attachments are available for some of these products, but most shops rely on labor-intensive, off-press methods, at least at first, to become familiar with adhesive-locked materials.

Ink color and opacity
You can generate creative effects when using some types of specialty inks as underlay colors that are then overprinted with conventional formulations. Communicate the desired effect to the production staff, and choose the appropriate combination of underlay and overprint colors.

Using flake-bearing or reflective inks as an underlay, for example, can lead to attractive designs with a deep, layered look. However, the overprinted color must be translucent so that light can penetrate the ink and reflect light from the metallic particles. Dense, opaque colors are typically needed for prints in which high-density inks are layered.

Screenmaking
Print quality begins in prepress. Design creation is an important part of it, but screenmaking is equally critical. High-quality positives are required, given the extended exposure times and tight registration associated with many types of special-effect inks. You need to produce the greatest degree of contrast in the dark, imaged areas of the film relative to the clear areas of the positive (high Dmax, low Dmin) to prevent light transmission into image areas and to provide maximum exposure in non-image areas.
With low-quality positives, the extended exposure times required for thick stencils used with special-effect inks are bound to cause problems. If you can’t generate top-quality positives, then you won’t be able to hold the registration needed for tight-tolerance applications such as lenticular garment prints.

Mesh selection and ink-particle size
The primary consideration when it comes to mesh selection is to ensure that mesh openings are large enough to accommodate specialty pigments or particles borne by the ink (Figure 1). Metallic flakes, glitter, solid particles, and even thicker ink formulations all require mesh that has larger openings and, possibly, a larger thread diameter.


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