Dyeing textiles makes them more attractive and functional. There are three main factors that define color: hue (the color name), value (lightness or darkness), and chroma (brightness or dullness). Dyes are applied to textiles through dyeing or printing processes. Various dye types include reactive, acid, basic, disperse and pigment dyes. Proper dye selection and dyeing conditions such as temperature, time and chemicals are required to achieve optimal color fastness properties. Color fastness testing evaluates how color withstands effects like washing, light exposure, rubbing and perspiration.

1. INTRODUCTION TO
DYEING

2. Why Textiles are Coloured ??
• Objectives
– Make textiles attractive for aesthetic appeal
– Functional application
• Camouflage fabrics for military
• Fluorescent jackets for road repairing personals
Life would be dull without colour

3. Defining a Colour
• Three terms are generally used to define a
colour
– Hue
– Value
– Chroma

4. • Hue
– This is the term to define the colour
– Example: Pink, Red, Blue etc.
• Value
– This is the term used to define the lightness, darkness,
tone or shades of the colour or hues
– Example: If a colour have a low value that means the
colour is light and vice – versa
• Chroma
– This term is used to indicate the depth (i.e. the
brightness/dullness, intensity) of the colour
– A colour of high chroma value will be very bright

5. Relationship between Hue, Value and Chroma
Weaker
Duller
Brighter
Stronger
Hue
Value
Chroma

6. COLOUR MIXING
• White light is the combination of 7 colours
– Violet
– Indigo
– Blue
– Green
– Yellow
– Orange
– Red

7. Additive Colour Mixing
• White can also be produced by mixing equal proportion of
red, green & blue colours
• Blue, green and red is thus known as primary additive
colours
• The others colours violet, indigo, orange and yellow are
made up of binary combinations of the primary additive
colours and thus these colours are known as secondary
colours

9. • 1 part of red + 1 part of blue + 1 part of green = white
1 part of red + 1 part of green = yellow
1 part of red + 1 part of blue = magenta
1 part of blue + 1 part of green = cyan
• Projecting the coloured light onto a white screen will confirm the following
2 part of blue + 2 part of yellow = white
2 part of green + 2 part of magenta = white
2 part of red + 2 part of cyan = white
• The additive nature of primary colours is utilized in colour television. The
colours one sees on a colour television screen are obtained by projecting
blue, green and red dots onto the screen.
• Stage lightening is another situation where additive colour mixing is used.

10. Subtractive Colour Mixing
• The mixing of dyes, printing pastes, paints and pigments is called
subtractive colour mixing
• The term ‘subtractive’ because colour is removed from each colour to
produce black
• The three subtractive primary colours are in fact secondary colours of
the additive colours

12. Ways of Adding Colour
• Dyeing
– The substrate is completely covered with colour
• Printing
– Colour is applied on discrete places
– Localized dyeing

13. SUBSTANCES USED FOR
COLOURING
• Dye
– Water soluble
– Certain dyes are attracted to certain fibre types
• Pigments
– Not water soluble
– Have no affection for any type of fibre
– Used mainly for printing or mass-colouration of
synthetic fibers

14. The constituents of dye
• Dye particles contains two portion
– Chromophores or colour bearing group
– Auxochrome or colour helping group
• The chromophores decides the hue or colour of a dye
molecule
• The auxochrome intensify the hue of the colour, makes the
dye molecule water soluble, improves its fastness
properties etc.

15. CLASSIFICATION OF
COLOURING MATERIAL

16. Colouring Material
Synthetic Dyes Natural Dyes
Water Soluble Water Insoluble
Dyes
Vat Dye
Disperse Dye
Sulphur Dye
Optical Whiteners
Reactive Dyes
Direct Dyes
Acid Dyes
Basic Dyes
Ingrain Dyes
Mineral
Oxidation
Colours
Azo Dye
Dyestuffs Pigments

17. COMMERCIAL DYES NAME
AND ITS SIGNIFICANCE

18. • Commercial dyes are compiled in a mammoth publication
• Colour Index of 5 volumes
• Dyes are classified based on the chemical structure and given a CI
(constitution number)
• Commercial dyes are also classified according to the application or
usage, in which they are given a CI Generic number along with its
colour

19. Nomenclature of Commercial Dyes
(Trade Name) (Colour or hue) (tone of the colour) (fast to light)
For Example:
Basacryl Yellow 7 GL
Basacryl Yellow 5 GL
Basacryl Yellow 3 RL
Basacryl Yellow 5 RL
Basacryl Yellow RL
Basic Dyes
Basic Dye
Yellow colour
Gelb i.e.
Yellow tone
Fast to Light
Depth of colour

20. Substantivity / Affinity & Exhaustion
• Substantivity / Affinity
– It is the attraction between the dye and the fibre at
given dyeing condition
– Indicates the ability of the dye to go from the solution
phase to the fibre
• Exhaustion
– Proportion of dye that has moved from the solution to
the fibre

21. M:L RATIO
• Material to Liquor Ration (M:L Ratio)
– This ratio refers to the ratio of the weight of fibre to be
dyed and the volume of the dye bath
– Example: M:L ratio for dyeing a particular dye / fabric
means for 1 Kg of dry fibre / fabric a dye bath of 10
Litres is required to acquire a particular shade

22. Example of M:L
• A material of 5 gm is to be dyed at a liquor ratio of 1:5.
How much dye liquor is to be prepared for the dyeing of
the material??
• Ans: Material weight = 5 gms
Volume of dye liquor required = 5 x 5 ml = 25 ml

23. PERCENTAGE SHADE
• Shade Percentage
– It can be defined as the quantity of dye taken for dyeing
expressed a the percentage of the dry weight of the
fibre/fabric/yarn to be dyed
Shade % = (Quantity of dye in gms / Dry weight of
fibre/fabric/yarn to be dyed) x 100%

24. Example of Shade %
• If a material is to be dyed for a shade % of 5%; how much
dye powder is required to be added in the dye bath? The
weight of the material is 10gm and the M:L ratio is 1:20
• The volume of the dye liquor = 20 x 10 ml = 200 ml
i.e. 5 = Weight of dye in gms x 100 / Wt of fibre
Or, Weight of dye required in gms = 5 x 10 / 100 = 0.5 gms

25. DYE AUXILIARIES

26. • Dyeing assistants or auxiliaries are the chemicals that
facilitates the production of required shades of dyeing
– Water
– Acid/ Alkali
– Carrier
– Water Softening Agent
– Exhausting Agent
– Dispersing Agent
– Levelling Agent
– Retarding Agent

27. • Water
– Water is used as the medium of dyeing
• Carrier
– Swells the fibre to enhance penetration of dye particles
inside the fibre structure
– Reduces the Tg (i.e. glass transition temperature)
• Acid / Alkali
– Adjust the pH to the suitable condition for the dye bath

28. Water Softening Agent
• Water softening agents are used when hard water is used in
dyeing process
• Hard water is due to the presence of metallic ions
• Softening agents react with the metallic ions in such a way that
they become a complex
• Example: Calgon (sodium hexa-metaphosphate) and EDTA are
most commonly used softening agents
• The formation of complex compounds is known as “chelation”

29. Exhausting Agents
– Facilitate the movement of dye molecules to the fibre
– Common salt (NaCl) or Glauber salt (Na2SO4.10H2O) is predominantly
used
• Direct, azoic,vat,solubilised vat and reactive dyes act as anionic dye (i.e.
splitting up into dye anion and metallic cations in water)
• When cellulosic fibre is immersed in water it acquires a negative electrical
charge
• The negatively charged fibre surface repels the negatively charged dye
particles present in water
• The positive ion released by the glauber salt / common salt reduce the –ve
charge of the fibre surface and facilitate the approach of the dye anions
towards the fibre surface

30. Dispersing Agents
• Help in producing uniform dispersed solution
• This is required for the colouring materials
– Not soluble in water
– Requires a uniform dispersed coloured solution or
application medium
– Example: Pigments are dispersed in the printing paste
with the help of dispersing agents

31. Levelling Agents
• Used to produce uniform, even dyeing on textile material
• Some dyes have the tendency to rush on to the fibre due to
their higher affinities for the fibre
– In such cases it is difficult to produce an even dyeing
under normal circumstances
– Levelling agents results in uniform uptake of the dye by
the fibre
• By retarding the movement of the dye particles
rushing towards the fibre

32. Retarding Agents
• These agents are used as levelling agents and acts
uniformly through the dyeing process
• Acts in one of the two ways
– Have some affinity towards the fibres but the affinity is
less in comparison to that of the dye to the fibres. So
initially there will be fewer dye sites available and even
dye uptake results
– Forms large complexes with the dye molecules and
reduces the rate of penetration of dye molecules inside
the fibre structure

33. DYE BATH
• A bath or container is required where the dye liquor colouring material
(dye) and colour assistant material is made of required quantity and
dyeing can take place at specified temperature and pressure
• Dyeing of textile materials is carried out in various forms like
– Loose stock of fibre (known as fibre dyeing)
– Yarn dyeing in form of hank, cheese, cone etc.
– Fabric (both woven and knitted)
– Garment

34. • Different types of dyeing machine is required for different forms of
textile material
– Loose stock dyeing machine (for fibre dyeing)
– Hank Yarn Dyeing Machine
– Yarn package dyeing machine
– Jigger (Fabric dyeing machine)
– Winch (Fabric dyeing machine)
– Jet Dyeing Machine (Fabric dyeing machine)
– Continuous dyeing range

35. Wash Cycles
• After the dyeing operation it is required to rinse out the chemicals,
neutralize the fabric and remove the superficial dyes from the surface
of the fabric to increase the fastness property
• The dyeing process therefore is followed immediately by
– Cold wash rinsing
– Hot washing with soap solution
– Cold wash
– Neutralization with acid solution
– Cold washing
• The no. of washes also depends on the type & depth of dye used and
the chemicals used during dyeing

36. TEMPERATURE CONTROL
• The effect of temperature is to activate the molecular vibrations in the
solute
– To exceed the critical energy necessary for them to make the
journey from the solution to the fibre
• Therefore, the increase in temperature will enhance the dyeing i.e. the
dyeing rate
• More is the temperature, less will be the time of dyeing i.e rate of
dyeing will increase
• However, the temperature should not be raised above a particular level
such that degradation of the fibre occurs

37. RATE OF DYEING
• The rate of dyeing means the amount of dye transferred
from the solution to the fibre. Amount of dyestuff absorbed
per unit time.
• The rate of dyeing depends on the following factors
– The temperature of the bath
– Concentration of salt in the bath
– Pressure of the bath(for polyester dyeing)
– Dye particle size
– M:L ratio

38. Compatibility of Dyes
• Dyes are compatible
1. When the ratio of absorption rate of two
dyes is constant .
2. When characteristics of colour fastness is
equal.

39. MECHANISM OF DYEING

40. Mechanism of Dyeing
• Adsorption of dyestuff on fibre surface
• Diffusion of the dyestuff through the internal structure of
the fibre
• Fixation of dye molecule

41. Adsorption
• Dye molecules move towards the fiber
• Get adsorbed on the fibre surface

42. Penetration
• Adsorbed dye molecule enter the fibre structure
• Gradually penetrate or ‘diffuse’ in the structure
• Rate of penetration depends upon the molecular structure
of the dye and dyeing condition
• Greater the penetration of dye in the fibre, better and
brighter is the dyeing
Cross section of fibre with poor
dyeing penetration
Cross section of fibre with good
penetration

43. FIXATION
• The final step where the dye molecules find suitable
locations, where they get fixed or ‘anchored’

44. FASTNESS PROPERTIES

45. What is Colour Fastness?
• Colour fastness is a term that describes the propensity of an
article to change or lose colour when treated in a certain way
Colour fastness is usually assessed separately w.r.t. :
• Change in colour of the specimen being tested, that is colour
fading
• Staining of undyed material which attaches to the specimen
during the test, that is bleeding of colour
Colour Fastness Evaluation

46. Colour Fastness Testing
 Colour fastness testing
– Colour Fastness to crocking / rubbing
– Colour Fastness to washing
– Colour Fastness to light
– Colour Fastness to Saliva
– Colour Fastness to chlorine bleach
– Colour Fastness to water
– Colour Fastness to Perspiration

47. • To check Staining on other fibre types multifibre
adjacent fabric is being used. It is made of yarns of
various generic kinds of fibres, each of which forms a
strip of specified width providing even thickness of
the fabric
Multifibre Adjacent Fabric
Wool
Acrylic
Polyester
Nylon
Cotton
Acetate

48. Visual Evaluation :Grey Scale
In order to give a more objective result, a numerical
assessment of each of these effects is made by comparing
the changes with two sets of standard Grey Scales
 Grey Scales for Colour Change
 Grey Scales for Staining

49. Grey scales
Grey scale for
colour
change
Grey scale for
staining

50. Interpretation of the grades
• The end result of any colorfastness test is a grade given to the
tested sample.
– Grade 5 - NO CHANGE
– Grade 4 - SLIGHT CHANGE
– Grade 3 - NOTICEABLE CHANGE
– Grade 2 - CONSIDERABLE CHANGE
– Grade 1 - SEVERE CHANGE

51. Conditions of Viewing
 The source under which
the comparison is made
is-
D65 - daylight
 The specimen should be
placed on a flat,
uniform surface having
no distortions. The
surrounding field shall
be uniform grey.

52. Conditions of Viewing
 The specimen plane is at 45° angle to horizontal. The light
is incident upon the surfaces at an angle of approximately
45°, and the direction of viewing is approximately along
the perpendicular to the plane of the surfaces
 For assessment, a piece of the original and the tested
specimen, or the undyed and stained adjacent fabrics, are
arranged side by side in the same plane and oriented in the
same direction