Dye is a coloured substance that chemically bonds to the substrate to which it is being applied. This distinguishes dyes from pigments which do not chemically bind to the material they colour. Dye is generally applied in an aqueous solution, and may require aftertreatment to improve the fastness of the dye on the fibre. Dyes are usually soluble in water whereas pigments are insoluble. Dyes selection is very important when dyeing different types of textile fibre. Types of chemical dyes are Direct, Reactive, Vat, Sulphur dyes etc. All dyes required different chemical auxiliaries and different after treatment process. Each dyes possess different light, washing & rubbing fastness and having different characteristics also.

1. Dyeing Process
And
its auxiliaries
Pandit Lakhmichand State University Of Performing &Visual Arts,
Rohtak

2. DYES & ITS CLASSIFICATION
Dyes

3. DYES SUITABLE FOR FIBER .

4. DYES & ITS CHARACTERISTICS

5. DYES & ITS FASTNESS

6. DIRECT DYES
Properties
❖These are readily soluble in water.
❖These are used for dyeing cotton and viscose.
❖Poor fastness to washing and light.
❖Cheapest dye.
It’s a amine group and it is directly soluble in water.
The exhausting agents are sodium chloride ( NaCl) and sodium
carbonate (Na2Co3) or Glaubers salt Sodium sulphate (Na2So4).

7. Recipe:
Dye - 1%
0-1 light, 1-2 medium, 2-3 dark.
M:L ratio 1:20
Nacl – 1%
Na2co3 - 1%
After Treatment
Soda ash and water- fixing agent
Time 1 hr
Temp – 60.

8. REACTIVE DYES
The reactive dye originally reacts and forms covalent bond with the
fiber and they are called as ‘Reactive dyes’. Because of the strong
covalent bond with the fibers, it has good fastness properties.
PROPERTIES
❖ It is water soluble. It dissolves, ionizes in water and forms negative
charged dye ion.
❖ Wide range of colours are available.
❖ It fixes with the fibre by forming covalent bond with the OH group
of cellulose.
• They have good fastness as mentioned below.
• Wash fastness - 4 – 5
• Rubbing fastness - 4 – 5
• Light fastness - 5 – 6

9. CLASSIFICATION OF REACTIVE DYES
 Hot brand dyes –
 Mono chloro tri azine dyes. These dyes have only one Cl-group as
the reactive group which needs higher temperature to be available
for reaction with fibre. Hence they are called as HOT brand dyes.
Ex: Procion H.
 Cold brand dyes –
 Di chloro tri azine dyes. These dyes have two Cl-groups and hence
they react with fibre even at room temperature. So they are called
as COLD brand dyes. Ex: Procion M.
 Vinyl Sulphone dyes – Ex: Remazol dyes.

10. DYEING PROCESS FOR COLD BRAND
 Dissolving the dyestuff
 The dye is taken as per the shade % and pasted with a little quantity
of wetting agent ( T R O ).
 Then warm water is added and stirred.
 Dyeing (Exhaust Method)
 The fabric is loaded in the machine.
 The water is filled as per M:L ratio (1:20).
 The circulation of material is started and Dye solution is added and
½ of 30-50 gpl Sodium Chloride or 20-30 gpl Sodium Sulphate
(Glabour salt) is added as Exhausting agent.

11.  It exhausts the dissolved dye from the solution and transfers the
same to the substrate.
 10-20 gpl Sodium Carbonate is added as fixing agent.
 This alkali enables the dye to form covalent bond with the fibre.
Allow for 30-60 min depending on shade.
 Hot wash at 50 C for 15 min
 Cold washing for 15 min
 Neutralize with 1% Acetic acid for 15 min
 Hot soaping in 5 gpl soap and
 1 gpl soda ash at 50 C for 15 min
 Cold washing for 15 min.

12. DYEING OF COTTON WITH REACTIVE HOT BRAND
 Dissolving the dyestuff
 The dye is taken as per the shade % and pasted with a little quantity
of wetting agent (TRO). Then warm water is added and stirred.
 Dyeing (Exhaust Method)
 The dyeing procedure in winch dyeing machine is explained below.
 The fabric is loaded in the machine.
 The water is filled as per M:L ratio (1:20).
 The dye bath is set at 40 C. The circulation of material is started.

13.  Dye solution is added. Steam is turned on and the temperature is
raised at the rate of 2 C per minute and ½ of 30-50 gpl Sodium
Chloride or 20-30 gpl Sodium Sulphate is added as Exhausting agent.
It exhausts the dissolved dye from the solution and transfers the same
to the substrate.
 The temperature at 70 C for 60 mins.
 10-20 gpl Sodium Carbonate is added as fixing agent.
 This alkali enables the dye to form covalent bond with the fibre and
time 30-60 min depending on shade.
 Hot wash at 50 C for 15 min. Cold washing for 15 min.
 These processes remove the surface deposited dye, hydrolyzed dye
and alkali from fabric.Neutralise with 1% Acetic acid for 15 min.Hot
soaping in 5 gpl soap and1 gpl soda ash at 50 C for 15 min
 Cold washing for 15 min.

14. VAT DYES
Properties
 It is insoluble. It can be solublised with the help of a strong
alkali(NaOH) and strong reducing agent(Hydrose).
 It is available as fine very fine and ultra fine forms.
 Narrow range of colours. Hence shade matshing is difficult.
 The colour build up is excellent and hence less amount of dye is
enough.
 It is the costliest dye.
 Fastness properties:
 Wash fastness-5
 Rubbing fastness-5
 Light fatness-7-8
The dyeing
carried out in
the following
four stages:
• Vatting
• Dyeing
• Oxidation
• soaping
• Natural –
Indigo plant

15. VATING
• In vatting the insoluble vat dye is converted into soluble leuco dye.
• The dye is taken as per shade and pasted with small quantity of non
ionic wetting agent 60C hot water is added and stirred.
• Sodium Hydro Sulphite or Hydrose and Sodium hydroxide are
added and stirred. Hydrose reduces dye into vat acid, which is
subsequently neutralized by NaOH and soluble sodium (Leuco
form) of dye is formed.
• Original colour of the solution change into reduce colour

16. DYEING
 Fabric is loaded in the machine.
 The dye bath is set up as per ML ratio.
 Bath temperature is raised to 50C. Circultion of liquor or material is
started. 2-4gpl of Hydrose and 2-4 gpl of caustic soda are added. pH
of the bath is 10-11 and 5 min
 The pre dissolved dye solution is added. Bath temperature ie raised to
90C-100C.The fabric should not expose in the atmosphere as the
oxygen in the air may oxidize the dye and cause ’patches’ add 10-20
gpl Glauber salt or common salt is added in two instalments with a
time interval of 15 minutes. The deing is continued for further 45min-
60min. Dye penetrates well into the fibre molecule.
 The material is squeezed. (It should be washed)

17. OXIDATION
 The leuco dye inside the fibre molecule is oxidized into its original insoluble
form.
 The dye molecule I mechanically trapped inside the fibre molecule and hence it
can not come out in subsequent washing. There are two types of Oxidation
namely.
 (i) Air oxidation
 (ii)Chemical oxidation
 In air oxidation the material is exposed to atmosphere air for 15 min.
 In Chemical oxidation the material is treated with 1-3 gpl sodium peroxide or
2gpl H2O2 with 1gpl acetic acid.

18. AFTER TREATMENT:
• The fastness of light and washing of sulphur dyes is improved by
after treatment with the following solution.
• It should be done for sulphur black.
• 1.25% Potasium dichromate-To improve wash fastness)
• 1.25% Acetate acid(60%)
• 1.25% Copper sulphate-To improve the light fastness)
• At 60C for 30 minS
• Hot soaping-5gpl sop and 1gpl Soda ash for 80C for 15 min
• Cold wah for 15 min.

19. ACID DYES
 The acid dyes are so called as they are applied in acidic condition.
 These dyes are particularly suitable to dye protein fibre like wool ,
silk and polyamide fiber (Nylon).
 They are sodium salt of sulphonic acid and hence it’s a water
soluble.
 They are water soluble.
 Wide range of colour is available.
 Wash fastness-5
 Rubbing fastness-5
 Light fastness-4

20. DYEING OF WOOL WITH ACID DYES
 Dye is taken as per shade % and pasted with a small quantity of wetting
agent. The dye bath is made up to M:L ratio.
 The temperature is raised to 50C. Dye solution is added.
 10 gpl glabour salt is added as levelling agent.
 5% sulphuric acid is added in two installments with a time interval of 15
min as exhausting agent.
 It ionizes the amine groups in the wool fibre as positive charged ions.
 They attract negative charged dye ions, which rush towards the fibre at a
faster rate leading to unevenness.
 The concentration of dye in the dye bath is maximum and to prevent this
rush, a retarding agent or leveling agent is added.
 The dye couples with the fibre with IONIC BOND.

21. DISPERSE DYES
PROPERTIES
 It is insoluble in water. It can be made as a fine dispersion with the
help of a dispersing agent.
 It is a sublimable dye. It becomes as ‘dye gas’ at very high
temperature.
 It has the smallest particle size. It has a wide range of colors.
 It is used to dye mainly polyester. It is used to dye nylon, cellulose,
acetate and other synthetic fibres.
Fastness properties
 Wash fastness – 5 Rubbing fastness – 5 Light fastness – 6-7

22. DYEING OF POLYESTERWITH DISPERSE DYES
Polyester is a non-ionic and highly crystalline fibre. Hence, it is
very difficult to dye. The molecules are packed very closely
and compactly. This close structure of fibre has to be opened
in order to allow the dye molecules to enter. Two principles
are employed to open the fibre molecular structure.
Thermal action – when the temperature is increased beyond the
certain level of the fibre, the molecular vibrations will be
excessive that provide enough openings in the fibre molecule
for the entry of dye molecule.
Swelling action – carriers and some solvents swell the fibre
molecule which inturn reduces the Tg as well as creates
‘pores’ for the entry of dye molecule which can make use of
low temperature dyeing.

23. HIGHTEMPERATURE HIGH PRESSURE DYEING
 Dye is taken as per shade % and pasted with a small quantity of
acetic acid. Hot water at 50c is added and stirred.The fabric is
loaded in the machine. The dye bath is made up to M:L ratio
(1:15). 1 gpl dispersing agent and 1ml/l acetic acid is added to
bring the pH 5-6. Temperature is raised to 60c and dye solution
is added.
 pH of the bath – slightly acidic (5-6). The temperature is
increased rapidly (4c per min) to 135c for which the steam
pressure is increased to 2 kg/sq.cm
 Dyeing is continued at 135c for 1-1 ½ hours.
 Hot wash – 10 min.
 Reduction clearing – 1 gpl hydrose and 2 gpl soda ash at room
temperature for 15-20 min. Surface deposited dyes are removed
completely.

25. Anil Kumar , Lecturer (Textile Design)
Pandit Lakhmichand State University of Perfo
Visual Arts , Rohtak
E-mail- anilkumar@plcsupva.ac.in
Mobile no. +919729138649
Thank you