Introduction:
Printing:
Printing could be referred to as a sort of selective dyeing that makes an
important contribution fabric decoration thanks to the combination of colors
and dyeing methods.
Printing
involves localized coloration. This is usually achieved by applying thickened
paste containing dyes or pigments onto a fabric surface according to a given
color design. In particular, the viscosity of print paste is critical. It
determines the volume of paste transferred to the fabric and the degree to
which it spreads on and the surface yarns.
Printing
was originally done by hand using wooden blocks with a raised printing surface,
much as children do potato printing.
Printing styles:
Style refers to the manner by
which a particular action is performed. Styles of printing mean the manner in
which a printed effect is produced.
The different styles of
printing are-
- Direct style of
printing.
- Discharge style
of printing.
- Resist style of
printing.
- Flock style of
printing.
- Burn out or
Devore style of printing.
- Crepon or crimp
style of printing.
In broad sense the styles of printing are classified
as-
1.
Direct style
printing
2.
Discharge style
printing
a.
White discharge
b.
Color discharge
3.
Resist style
printing
a.
White resist
b.
Color resist
1. Direct style of
printing:
In
this style the dyes are applied directly at the required places of the fabric,
leaving the other portion white, by any printing method like block printing,
screen printing etc. so this style is called direct style of printing.
Direct
style involves transfer of paste containing dyes to the appropriate areas of
the fabric. After drying the required localized dyeing of the fibers occurs
during steaming. Washing follows to remove the paste residue. In case of
pigment printing the pigments adhere to fabric surface with the cured binder
film. No additional treatment is needed.
Direct printing is the most important type of printing. It
may even take place on a uniformly dyed fabric to produce particular color
effect. Such over printing produces are called ‘fall on ‘effects.
Advantages:
- It is the easiest printing style to operate.
- Least expensive.
- Suitable for the printing of both simple and
complicated design and
- Color matching with the original design sketch
is easy.
2. Discharge style of printing:
Discharge means removal and
discharging system means the process which can produce a white or colored
effect on a previously dyed ground.
This discharging of color from
previously dyed ground is carried out by a discharging agent which is actually
a oxidizing and reducing agent capable of destroying color by oxidation and
reduction.
The discharging agent’s are-
a.
Oxidizing agent: Potassium chlorate, Na-chlorate
b.
Reducing agent: Rongalite-c, Stannous chloride
Discharge printing is a method
where a dyed fabric is printed with discharging agents which selectively
destroy the dye. A white discharge is produced.
An alternative method is to print
along with discharging agent, non dischargeable dye which gives a colored
discharged surrounded by a ground color.
There are two types of
discharge style printing such as-
a. White discharge
After dyeing and printing the discharging agent
discharges the dye of printed area and leaves the dye of unprinted areas
unaffected. So a design is produced on the color ground.
b. Color discharge:
Dye stuff which is strongly resistant to
discharging agent are included in the printing paste along with discharging
agent. The discharging agent of print
paste discharges the color at the printed area. At the same time the dye stuff
of print paste deposits and fixes itself on the ground. As a result of color
discharge effect is obtained. In this way one or more colors may be applied.
Advantages:
- Large areas of ground of ground color are
possible.
- Delicate colors and intricate patterns possible
on deep ground color, excellent depth and clarity possible.
- Higher production cost but long lasting unique
styles.
3. Resist style printing:
Resists means to hinder. In this process a
chemical is applied to the fabric that will prevent the fixation of any
coloring agent employed afterwards on that area.
It
is one of the oldest printing style in which two resulting pattern can be
obtained.
In
resist printing the fabric is first printed with an agent that resists either
dye penetration or dye fixation. During subsequent dyeing, only the areas free
of the resist agent are colored.
There are two types of resist
printing such as-
White resist: if no color is
added in the printing paste solution along with resist salt, after dyeing the
printed areas remains white. This is called white resist.
Color
resist: if any coloring material is added in the print paste along with
resist salt, after dyeing the printed areas contain the color added to print
paste and the remaining areas will contain the color of the dye solution. As a
result colored resist effect is obtained.
Advantages:
a.
can use white or
colored resist
b.
can use dyes of
much higher stability than those used in discharge printing & therefore
much higher fastness can be obtained.
c.
Non dischargeable
dyes can be used for the ground color.
4. Flock style of printing:
Flock printing is a process in which a flock
is fixed onto a cloth by means of adhesive to form printed pattern. It produces
a pile or velvet effect on the fabric similar to form a printed pattern.
Flock
is branch of short fiber. In the electrostatic method of flocking the fabric is
printed with an adhesive and passes on a moving belt through an electric
charge. The flock made from cotton, rayon and synthetic is filtered from the
flock hopper on to the fabric and is attracted to the adhesive in perpendicular
form. After a backing process the sharp less fiber s are removed.
5. Burn out or Devore
style of printing.
Burn-out printing is also called Transparence
process, Corrosion Process or Carbonization Printing (in Japan). Being printed
by the printing paste which is mixed by a kind of chemical. After proper
process, one of the fibers in the fabric will be destroyed. Then it comes into
being a burn-out fabric of a particular and translucent style.
The production of burn-out printing has a transparent and a concavo-convex
feeling. With a natural printing pattern and unique style, it just looks like
the organdie which is half transparent, colorful and shiny.
6. Crepon or crimp style of printing:
This style is characterized
by the appearance of alternate plain and crinkle stripes in the fabric itself.
This effect can be brought about by localized fabric shrinkage with appropriate
swelling agent.
For example, if cotton fabric
is printed in a striped pattern with strong caustic soda, it shrinks in the
printed areas and thus causes the unprinted areas to crimp. The greater the
shrinkage or contraction of the printed areas, the more pronounced the effect
becomes.
Conclusion:
Printing,
like dyeing, is a process to applying color to a substrate.however instead of coloring
the whole substrate as in dyeing; print color is applied only to defined areas
to obtain the desired pattern. This involves different techniques and different
machineries with respect to dyeing, but the physical and chemical processes
that take place between the dye and the fiber are analogous to dyeing.