Impressions - June/July 2017 - 29

By Rick Davis,
Contributing Writer

Learn how to ensure designs - even
specialty prints - yield maximum color intensity.
nderbasing has been standard in screen printing on dark garments
for about 40 years. The application involves printing a light base to
help overprinted colors hold their intensity.
Initially, white underbases were printed as a solid area through mesh
counts as low as 60 monofilament or 6XX. The result was an opaque,
solid ink film, which also resulted in a harsh hand. This process evolved,
with printers using finer meshes, softer inks and alternative ink technologies - all of which culminated in soft-hand prints.
Today, printers use underbases through screens with mesh counts as
low as 255/100, combined with halftones and different media to achieve
the maximum effect with the softest possible hand. Underbasing has
become an art, which some have mastered and others strive to learn.
The primary components needed to achieve a successful underbase are:
* A high-opacity ink
* Proper mesh selection
* Properly tensioned screens
* Proper flashing techniques

Screen Selection
Because underbases are known for adding to ink-film thickness
and the garment's hand, the objective is to produce an underbase

with the thinnest-possible ink film. A newer industry innovation
is "S" mesh, a standardized monofilament polyester mesh count
with a thinner thread diameter. This mesh type allows for greater
ink flow while depositing a thinner ink film with a softer hand.
It also allows cooler and faster flashing.
Another important aspect of underbasing is using properly
tensioned screens that allow printing with minimal squeegee pressure and faster strokes, which all contribute to a print's softness.

Standard Underbasing
In addition to producing an opaque, light-colored surface or texture
on which colors can be printed to hold their intensity, an underbase
also can act as a dye blocker against synthetic or specialty-dyed fabrics,
such as sublimated polyester or pigment-dyed garments.
The ultimate objective is to produce the desired result - be it
aesthetics or product performance - with the thinnest-possible ink
film. In many cases, excessive ink films are printed in the name of
controlling dye migration, but they won't properly cure. This still results in dye migration and even poor washability. Thinner ink films,
however, produce a softer hand, flash faster and cure more readily.

Printing Parameters
A cotton or low-bleed ink can be used
as a standard T-shirt underbase for an
overprint on 100% cotton or 50/50 blends.
The desired parameters are:
1. Highest-possible mesh count for
the graphic. When printing a solid ink
film, you can use mesh counts from 155
to 305, depending on the art. Using a
thinner thread ("S" mesh) will deposit
a thinner ink film on the fabric surface.

This shows a special-effects print
using 3-D bases with 200 micron
stencils. Photo courtesy of Bimm
Ridder, Cedar Rapids, Iowa.

JUNE/JULY 2017

P.29

Impressions - June/July 2017

Table of Contents for the Digital Edition of Impressions - June/July 2017