The document is an assignment on the various assistants used in the printing process for textiles, detailing their functions and examples. It covers ingredients ranging from dyes and thickening agents to acids and miscellaneous agents, highlighting their roles in achieving effective printing results. The conclusion emphasizes the necessity of these assistants in the production of printed fabrics.

1. An Assignment
On
“Study on the assistants used in the printing process”
Course Title: Wet Processing II
Corse Code: WPE 323
Submitted To:
Dr. A K M Saiful Islam
Assistant Professor & Head
Department of Textile Engineering
City University
Submitted by:
Md. Zahid Hasan
ID: 173375179
Batch: 37th
Program: BSTE
Submission Date: 14th
November, 2020

2. Introduction: Printing means localized application of dyes on the fabric according to design.
For printing it is required to produce printing paste. Printing paste is a viscous paste which is
made from pigments, thickeners and many of chemical. A good printing paste is mainly
responsible for good printing effect. So it is very important to make a printing paste. There are
different types of ingredients are used to make printing paste.
Assistantused in printing process andtheir function:
1. Dyes/ Pigments:Dyes or dyestuff may be defined as colorants in which the coloring
substance is dissolved in liquid, are absorbed into the material to which they are put in an
application for. Pigments consist of extremely fine particles of ground coloring matter suspended
in liquid which forms a paint film that actually bonds to the surface it is applied to.
Functions:
 Attraction of dyestuff to the fiber due to presence of auxochrome.
 To achieve color effect on the fabric.
 To produce required shade.
Examples: Vat, Azoic, Reactive, Direct dye etc.
2. Wetting Agent: Substances which reduce the surface tension of water, thereby allowing it to
wet a surface easily, which are otherwise non wettable are known as wetting agents or surface
active agents.
Functions:
 To wet the fabric as well as dyestuff.
 To reduce surface tension of water allowing the dyestuff for easy penetration into fiber.
 To obtain smooth paste.
 To dissolve the dyestuff in the paste.
Examples: Olive oil, T.R oil, Caster oil, Lissapol N, Animal oil, Glycerine.
3. Solvents/Dispersing agents/Solution acids: This prevent aggregation of the dye stuff
molecules in the highly concentrated paste of the dye, solution aids increase the solubility of
insoluble dyestuff, solvents increase the color value of the prints, assist dye penetration and helps
to get bright design.
Functions:
 To get bright design,

3.  To assist dye penetration,
 To spread dye molecules evenly in the paste,
 Assist dye fixation,
 To prevent aggregation of dye molecules in the highly concentrated of the dye.
 To prevent precipitation.
 To increase solubility of the dyes.
 To make proper printing shade.
Examples: Urea, Glycerine, Desirable, Alcohol, Acetone, Diethylene glycol, Thio diethylene
glycol.
4. Thickener: Thickener is a thick mass which imparts stickiness and plasticity to the print
paste so that it may be applied on the fabric surface without bleeding or spreading and be capable
of maintaining the design out lines.
Thickener gives the required viscosity to the printing paste; prevent premature reactions between
the chemicals contained in the print paste.
Function:
 To give required viscosity to the printing paste
 To prevent premature reactions between the chemicals contained in the print paste.
 To hold the ingredients of the print paste on the fabric
Examples: Na-alginate, Fine gum, British gum, CMC.
5. De-foaming agents:De-foaming agents prevent the formation of foam during printing.
Function:
 To prevent the foam generation during printing
Examples: Silicone, Defoamers, Sulphated oil, Perminol KB, Emulsified pine oil.
6. Oxidizing agents:Oxidizing agents develop final color in steaming or in the subsequent after
treatment, assist in color fixation etc.
Function:
 To develop the final color during steaming or in the subsequent after treatment.
 Assists to dye fixation.
Examples: Sodium chlorate, Potasium chlorate, Sodium nitrate, Resist salt, Ammonium chlorite,
Ludigol, Na or K dichromate.

4. 7. Reducing agents:Reducing agents destroy color of the fabric.
Function:
 Used for reduction of different dyes.
 Used for mainly in discharge printing.
 To destroy color from the ground of fabric.
 To make the insoluble dyes to soluble.
Examples: Sodium hydrosulphite, Stanus chloride etc. Rongolite-C.
8. Catalyst and oxygencarrier: These prevent fibre damage, during steaming; accelerate the
final color development by oxidation.
Function:
 To prevent fiber damage during steaming.
 Accelerate the final color development by oxidation.
 Reduce the risk of oxidation.
Examples: Copper sulphide, Ammonium vanadate, Potassium ferrocyanide.
9. Acids/Alkalis: Acid is used to control PH below 7.0 in the bath. Alkali is used to control PH
above 7.0 in the bath.
Function:
 To maintain pH.
 To develop the color or printed fabric.
 To fix dye on the fabric permanently.
Examples: Organic acid, Alkali KOH, NaOH, Na2CO3, Pottasium carbonate, Sodium
bicarbonate, Sodium acetate.
10. Swellingagents:A swelling agent is a three-dimensional network of hydrophilic polymer
chains that are chemically or physically cross-linked.
Function:
 To create the big size holes of the fibers.
 Helps to swell the fiber structure.
 To reduce crystallinity.
 Help the easy penetration of dye molecule inside the fiber polymer.
Examples: Polyethylene glycol, Phenols, DEGDA (Di-ethylene glycol diacetate)

5. 11. Carrier:It is used to swell the fibres so that dyestuff molecules can diffuse in them easily.
Function:
 Used for fixing disperse dyes on polyester or polyester wool blends at temperature below
105oC.
Examples: Diphenol, Ortho-phenol, Tri-chloro benzene
12. Miscellaneous agent: It is colourless, solid, crystalline and very soluble in water. It has dye
solvent and hygroscopic properties. It also help to wash out thickener film from the fabric after
printing.
Function:
 Assist fixation of dyes.
 Absorb moisture from air.
 Facilitates subsequent washing off.
Examples: Urea, Glycerine etc.
Conclusion:In printing operation it is nessesery to used different types of printing asisstant or
ingredients. To produce printed fabric or clothes are used different kinds of printing ingredients.
In this assignment will be very helpful to know about assistant/ ingredients used in printing
operations.