1. Discharge Printing

2. Prepared By : Mazadul Hasan sheshir
ID: 2010000400008
13th Batch (session 2009-2013)
Department : Wet Processing Technology
Email: mazadulhasan@yahoo.com
Blog : www. Textilelab.blogspot.com (visit)
Southeast University
Department Of Textile Engineering
I/A 251,252 Tejgaon Dhaka Bangladesh
Prepared By :
©right

3. Fabrics are dyed a solid color prior to printing. When printing is done, the design is
applied by screen or roller with a chemical which removes the color of the originally
dyed fabric. Discharge prints can be made with rollers and screen methods. They are
not widely used because production costs are high.
Discharge Print

4.  Textile printing is the process of applying colour to fabric in definite patterns or
designs. In properly printed fabrics the colour is bonded with the fiber, so as to
resist washing and friction.
 Textile printing is related to dyeing but, whereas in dyeing proper the whole
fabric is uniformly covered with one colour, in printing one or more colours are
applied to it in certain parts only, and in sharply defined patterns.
 In printing, wooden blocks, stencils, engraved plates, rollers, or silkscreen’s can
be used to place colours on the fabric. Colourants used in printing contain dyes
thickened to prevent the colour from spreading by capillary attraction beyond
the limits of the pattern or design.
 Traditional textile printing techniques may be broadly categorized into four
styles:
Introduction

5.  Direct printing, in which colourants containing dyes, thickeners, and the mordants
or substances necessary for fixing the colour on the cloth are printed in the
desired pattern.
 The printing of a mordant in the desired pattern prior to dyeing cloth; the color
adheres only where the mordant was printed.
 Resist dyeing, in which a wax or other substance is printed onto fabric which is
subsequently dyed. The waxed areas do not accept the dye, leaving uncoloured
patterns against a coloured ground.
 Discharge printing, in which a bleaching agent is printed onto previously dyed
fabrics to remove some or the entire colour.
 Resist and discharge techniques were particularly fashionable in the 19th century,
as were combination techniques in which indigo resist was used to create blue
backgrounds prior to block-printing of other colours.[1] Most modern
industrialized printing uses direct printing techniques.
Introduction

6. Discharge Printing
Discharge printing is a process where printing of lighter colors is done onto fabrics
having darker background. The dye in the garment is removed by replacing it with ink
which leaves a soft texture on the fabric. Discharge printing works best on cotton fabrics
because other fabrics are dyed in different processes and react less to discharge
chemicals and therefore the dye does not break down.
Initially in discharge printing, the finished goods required steaming during the drying
process which discouraged the practicing of this process. But the latest discharge ink
systems react chemically and do not require steaming. These latest systems brought
advancement and brought new openings in the area of screen printing.
Discharge Printing

7. The casino table’s graphics are done with discharge printing to avoid the hindrance of
the printed line when the dice is rolled. If at all the printing is done with plastisol it
would change the speed of the rolling dice. The discharge print gives a smooth run
for the rolling of the dice.
Discharge printing produces vibrant, opaque colors on dark color fabrics. The
depth, levelness and penetration can be controlled in discharged printing. Complex
patterns and soft colors can be produced with immense clarity.
Discharge printing is best observed when the four color printing is done on black
100% cotton shirts. The print appears best only when it is exposed to the heat
chamber.
Discharge Screen Printing
Discharge Printing

8. Required Fabric for Discharge Printing
Discharge printing enables a clean and transparent print than the earlier discharge addictives
which were used only for water base inks. Reduction is the keyword for discharge printing.
The method of discharge printing changes from fabric to fabric, but the best fabric for this
method is a pure cotton one.
Discharge all over Printing
Zinc-formaldehyde is used to remove the dye in the discharge process. Therefore, it is necessary to wash the t-shirts before you
wear them. Zinc- formaldehyde free discharge is also available which does not need any washing before wearing it. This is proved to
be a better process than the ordinary discharge printing process.
Use the right kind of fabric.
- The fabric has to be 100 percent natural like cotton.
- The dye on the fabric should be easily discharged. Cotton gives wonderful results in this process.
- The fabric should be dyed right avoiding over dyeing. This generally happens when there is shortage of dye and therefore
another color is dyed on top of this color. So when we try to discharge it, it results in the color which is below it.
It is important to check the fabric before starting the process. The fabric should be strong enough to carry the discharge process.
Required Fabric for Discharge Printing

9. Discharging agents :--
Clearly, the most important methods of discharging are based on reduction. This
general method can be varied and adapted to give discharges with most classes of
dye in use and on most types of fibre. Indeed, to many printers the terms ‘reducing
agent’ and ‘discharging agent’ are synonymous.
The most widely used reducing agents are the formaldehyde sulphoxylates. The
stability of these compounds is such that only limited losses of sulphoxylate occur
during printing and prior to steaming. The use of sodium formaldehyde sulphoxylate
(CI Reducing Agent 2, sold as Formosul or Rongalite C) was established as long ago
as 1905, when it was recognized that methods based on this reducing agent offered
many advantages.
Discharging agents

10. Importance of Discharge Styles
Discharge styles have been important since the earliest days of textile printing..With
any industrial process there must be sound technical and commercial reasons for its
conception and continuation. In the case of discharge printing, the following
considerations determine the usefulness of the process compared with other printing
techniques.
1. Printed materials with large areas of ground colour can be produced, the depth,
levelness and penetration of which would be difficult, if not impossible, to obtain
by a direct printing process.
2. Delicate colours and intricate patterns can be reproduced on grounds of any
depth, with a clarity and sharpness that have become the hallmarks of this style.
Intricate white patterns lose their crispness if left as unprinted areas in a direct,
blotch print, because the print paste spreads unequally in different directions. In
addition, a coloured motif fitted into a blotch print either leaves unprinted white
margins or forms a third colour where fall-on occurs. In some cases such effects
are acceptable, but they can be eliminated by using the discharge technique.
Importance of Discharge Styles

11. 3. The extra processes required and the additional costs of discharge pastes mean
that production costs are higher, but the aesthetically superior results give the
product a higher value and enable profit margins to be maintained or even
improved. The higher costs of discharge printing are often offset when applied to
long-lasting designs used for scarves, ties, cravats and dressing gowns. As already
indicated, in discharge styles the pattern is produced by the chemical destruction
of the original dye in the printed areas. The discharging agents used can be
oxidising or reducing agents, acids, alkalis and various salts. An early and, one
might say, classical example is the discharge printing of cotton dyed with indigo,
the characteristic colour of which can be destroyed either by oxidation or
reduction.
Importance of Discharge Styles

12. Discharge Screen Printing
Discharge is a screen printing process where the same techniques and equipment
are used but instead of normal ink, discharge inks are used, which remove the shirt's
dye instead of putting a color on top of the shirt. It is somewhat similar to bleaching
in a design, except it doesn't damage the fibers like bleaching would. It results in an
extremely soft print, and shows the weave of the shirt. It can be used by itself, as an
under base for other colors to be put on top, or with pigments added. Pigmenting
discharge can be difficult to achieve exact color results, as the discharge efficacy
affects the color, and what you see is not what you get when mixing the pigments,
but it can still be a great way to achieve colors on dark garments.
The discharge screen printing involves the following steps:
1. First the table is prepared by stretching the cloth and pinning it up on the
table.
2. Now the paste is prepared to discharge the dye on the fabric. Remember to
get your discharge paste ready a few hours before the process takes place.
3. Prepare the color discharge paste and apply on the fabric so that the dye
becomes soluble and comes out before the fabric is ready for steaming.
Discharge Screen Printing

13. 1. Print the fabric and keep it for drying, steaming should be done within 24 hours to
produce best results.
2. Once the steaming process is done, then wash the fabric thoroughly to get rid of
the chemicals. Hang the fabric and allow it to breathe for about 30 minutes, this
helps in developing color.
3. There you go!! The final wash is here. Wash the fabric in detergent to prevent
loosing of any vat dye left on the fabric which helps in fixing the dye to the fiber. It
is recommended to wash the fabric in slight lukewarm water.
Discharge screen printing is a long process and cannot be carried at home as there are
chemicals used in this process. They have to be handled carefully by trained staff with
perfection and patience.
Discharge Screen Printing

14. Positives of Discharge Screen Printing
1. Very cool technique that removes the dye from the shirt
2. Little to no feeling of the print on the shirt
3. Vibrant colors
4. The best way to print on dark shirts with non-traditional inks
5. Something different from screen printing "norms"
6. Still able to do a great amount of detail
7. We offer discharge printing at no additional charge. In fact, it's often
cheaper than traditional ink
Positives of Discharge Screen Printing

15. Negatives of Discharge Screen Printing
1. Some sizes may discharge better than others
2. Can be hard to use for photographic style or process printing
3. Only works on natural fibers, like cotton, so 50/50 can't be used
4. Not all shirt colors will discharge (royal blue never works well, for
example)
5. Process can be quirky
Negatives of Discharge Screen Printing

16. How Cotton & Polyester Give Discharge Printing Different Looks
How Cotton & Polyester Give Discharge Printing Different Looks
Discharge ink will not discharge polyester, but that doesn't mean we can print
discharge on polyester.
With water based and discharge ink, not all fabrics were created equal. 100% cotton
will give different results than a 65/35 cotton/poly blend will and a 50/50 different
yet. On top of that, as well look at below, two 50/50s from the same manufacturer
can yield very different results.
It’s important to know, or at least have an idea, how these different options will
affect the print style used because it will vary the end look drastically.
Since discharge ink will only “discharge” cotton and not polyester, that piece of
knowledge alone will be the basis for analysis here. It’s important to know that and
then apply it to different scenarios. For example, let’s say we have a design which
you want to print on a black shirt. Let’s look at a few shirt options and how each can
yield different results.

17. American Apparel 2001 Black Since this is a 100% cotton shirt we know this will discharge
with rather bright, bold, true colors. There shouldn’t be too many surprises here.
American Apparel BB401 Black With this shirt being a 50/50 cotton/poly blend, we need
to consider the fabric makeup to decide how it will print. This shirt is both cotton dyed as
well as poly dyed. That means the cotton and the poly in the shirt are both dyed, in this
case both dyed black. So, we’d only be able to get a bright discharge printing result from
the cotton portion of that shirt, since that’s all we can discharge. The poly portion of the
shirt won’t discharge so it’s not going to give bright printing results on a black shirt. The
end result on this print will be darker, faded, muted vintage look rather than the bright
bold print the 2001 delivered.
American Apparel BB401 Heather Black This is the same shirt we just looked at, but this
time it’s heather black, not straight black. We now have a shirt which is only cotton dyed,
not poly dyed as the black BB401 is. What that means is that the cotton part of this shirt is
black and the poly is nearly white. So we can discharge the black cotton to get bright print
colors and the poly is white which we can get bright colors out of. Therefore, this shirt will
yield rather bright, true looking colors even though its 50/50.
How Cotton & Polyester Give Discharge Printing Different Looks

18. This is obviously just a tip of the iceberg when it comes to shirt options yielding
different looks. We didn’t touch on discharging tri-blends or 65/35 blends, both of
which can be equally exciting. Overall, discharging 50/50s, 65/35s and tri-blends
can be an awesome process, but it does take some experimenting.

19. Points to be Considered for Discharge Printing
It is necessary to know the following points:
1. You should never overlap the colors if you want to print spots on the fabric.
2. Always go for transparent colors to show the dark background on the fabric. If you
want to separate colors then go for primary colors as they produce good results.
3. Discharge printing is mainly economical for all-over prints because it is done by soft
hands.
Points to be Considered for Discharge Printing

20. Conclusion
The discharge printing process is slightly more expensive because of the inks and
chemicals used as well as a slightly more difficult process but the end result leaves
that super soft feel that everyone wants! Works great for oversize designs with a lot
of coverage so when wearing the shirt, you’re not wearing that extra unbreathable
ink since the discharge print is actually part of the garments
Conclusion

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