2. Preparation depends on
The level and type of impurities.
The chemical used in various stages of
preparation.
The water supply
The type of machinery used.

4.  Objects of Singeing
• Process of burning off protruding fibres from the surface of yarn /
fabric
• Improve the lustre and smoothness of the material
The “fuzz” or the protruding fibres are responsible for
• Scattered reflection and hence contributes to a dull appearance
• Removal of fuzz results smooth surface and regular reflection of
light is obtained
• Uniform surface reflects more light and more uniformly and
produces lustrous surface

7.  Gas Singeing Machine
• The cloth is passed over two or more flames / burners
• The flame burns the protruding fibres without
damaging the cloth
• The speed of the transmission of the cloth hence is to
be adjusted carefully
• The fibres ends present in the interstiches between
warp and weft are also singed
• After passing through the flames the fabric is passed
through a trough of water
• Speed: 80 to 125 mts / min

8.  Advantages
• Both sides of the cloth are singed simultaneously
• Uniform singeing is obtained
• Fibres in the interstices between the warp and weft
threads are also burnt effectively
 Disadvantages
• Great risk of fire

9. flame intensity
fabric speed
fabric temperature
singeing position
hairiness measure

10. BEFORE SINGEING AFTER SINGEING

11.  Onto free guided fabric:
Flame meets right-angle
onto dense woven fabric
freely guided between 2
rollers, recommended for
natural fibres and blends
weighing more than 125g/m²

12.  Tangential singeing
Flame passes
tangentially over the
fabric bended over a
water cooled roller
recommendable for
fabrics which cannot
tolerate direct
exposure to flame .

13.  Onto water cooled roller
Flame meets right-angle
onto the fabric bended
over a water cooled roller.
Recommended for fabrics
of temperature sensitive
fibres, those of open-
weave, blended ones
weighing less than
125g/m

14.  Fabric heavily vibrates
due to the beating
bars.
 Dust, fibres and other
residues get loosened
and are extracted,
fibres sticking to the
surface get lifted by
the brush segments.

15.  Singeing Machines
• Hot Plate Singeing Machine
• Roller Singeing Machine
• Gas Singeing Machine

16.  Hot Plate Singeing Machine
• Consists of 2 to 3 curved copper plates
• Plates are kept red hot by some heating arrangements under
them
• The fabric is passed through the hot plates
• After passing the last hot plate, the cloth is immediately passed
through a water trough
• Speed: 180 mts / min
Hot Plate

17.  Advantages
• Suitable for back filling finishing process as the fibre
ends in the interstices are not removed
 Disadvantages
• Fibres ends in the inter-stitches of warp and weft are
not singed
• Causes uneven singeing due to difficulty in
maintaining uniform plate temperature
 Local cooling

18.  Roller Singeing Machine
• Similar to hot plate singeing
• A large heated cylinder is used in place of copper plate
Heated
Cylinder

19.  Advantage
• Uneven singeing will take place at lesser extend w.r.t
hot plate singeing machine
• Suitable for back filling finishing process as the fibre
ends in the interstices are not removed
 Disadvantages
• Local cooling therefore, difficult to maintain an even
singeing along the length and width of the fabric
• Fibre ends in the interstices of warp and weft threads
are not singed

20.  Yarn Singeing
• Yarns can also be singed
• The singeing in this case is also known as ‘gassing’
• The singed yarn is thus known as ‘gassed yarn’
• Yarns typically singed
 Combed cotton yarn
 Sewing thread
 Polyester cotton blended yarn
 Hosiery yarns meant for knitting

21. The purpose of desizing is to eleminate the
sizing product.
Main characteristics of sizing
Reduction friction
Good film formation
Water solubility
Non foaming
Low cost
Easily removable.

22. Starch
Polyvinyl Alchohol
Carboxymethyl cellulose
Polyacrylates
Polyester

23.  The objective of de-sizing is
• Remove the size material from grey fabric
• Fabric could be effectively scoured and bleached

24.  Mechanism of De-sizing
• Starch is having both straight and branched chain polymers due to
which it is insoluble in water and cannot be removed easily
• Starch can be made soluble in water however, if it can be reduced
to more shorter chained compounds
• Thus, under suitable conditions starch can be progressively
hydrolyzed or broken down
Starch Dextrine Maltose Glucose
(High Molecular Weight) (Low Molecular Weight)

25.  In de-sizing the hydrolysis is carried up to soluble dextrin
stage
 Starch changes to soluble dextrin in the de-sizing stage
 Since starch acts as a binder for the other ingredients, as
soon as starch is removed other ingredients will also be
removed
 It is to be noted that de-sizing is a chemical process and
its can be controlled by varying the concentration of the
de-sizing liquor

26. Methods of De-sizing
Desizing Methods
Hydrolytic Methods
• Rot Steep
• Enzymatic
• Acid Steep
Oxidative Methods
• Chlorine
• Chlorite
• Bromite
Novel Methods
• Solvent
• Low temperature Plasma treatment
• Desizing 2000

28. Tegwa Grade
Scale
Colour Starch
content%
1 High Blackish Blue 2.5%
2 Navy Blue 1%
3 Royal Blue 0.6%
4 Normal Blue 0.35%
5 Sky Blue 0.2%
6 Sea Blue 0.125%
7 Whitish Blue 0.085%
8 Dim Blue 0.06%
9 Full white 0.04%

30.  The amount of starch present is calculated
 The Tegwa value is evaluated
 Tegwa scale have 9 readings from 1 to 9
 A reading of 1 means the starch content is very high (around 2.5%)
and a value of 9 means the starch content is very low (0.04%)
 The test is known as “Iodine test for starch” or “Tegwa violet
scale”
 Iodine is added to the de-sized fabric
 The colour of the fabric will change and the colour is matched with
the Tegwa scale to evaluate out the Tegwa value

31. Lower degree of whiteness
Insufficient absorbency
Spots
Unlevelness.
Ring dyeing
Continuity is less

32.  Rot Steep Method
• The fabric is immersed in warm water at 400C and allowed to
stand for 24 hrs
• The micro-organisms present in atmosphere will secrete the
starch liquefying enzymes
• The enzymes will hydrolyze the starch
• The hydrolyzed starch can be removed by subsequent washing
 Advantages
• Very economical process
• Do not require and chemicals

33.  Disadvantages
• Requires large floor space
• Slow process
• There is a danger of mild dew attack and weakening
the cloth if steepening is not properly monitored
• Not reproducible

35.  Acid De-sizing
• Dilute Sulphuric acid or Hydrochloric acid is used
• The acid hydrolyze the starch present in the sized fabric
• After impregnation in weak acid and followed by squeezing the
fabric is to be kept for 2 – 3 hrs for hydrolysis of the starch
• Followed by washing to remove the acid
• Special care should be taken to avoid local evaporation of liquor
 Leads to increase of acid concentration
 Tendering of fabric will take place
Recipe: Mineral Acid – 0.5 to 1 %
Temperature – 300C
Dwell time – 60 – 120 mins

36.  Advantages
• The process is economical
• Quicker than rot steep method
• Can be performed at room temperature
• Reproducible
 Disadvantages
• Care must be taken to prevent the tendering of the
fabric (avoid local drying)

38.  Enzyme de-sizing
• The enzymes liquefy the starch in the fabric
• Enzymes are type of protein
• It acts as a catalyst in chemical reaction
Animal
Vegetable
Malt Extracts Bacterial
Viveral Diatase Raddase
Novofermosal Maltostase Bidlase
Clotted blood, liver etc. Diastafore Taka

39. Enzyme suffer from the disadvantage that if the conditions of
temperature
and pH are not maintained, little or no de-sizing will take place
Enzyme pH Concentration Temperature
Malt extracts 6 – 7.5 3 – 20 50 – 60 oC
Pancreatic 6.5 – 7.5 1 – 3 50 – 60 oC
Bacterial 5.5 – 7.5 0.5 – 1 60 - 70 oC

45. Average American Egyptian Primary
Wall
Cuticle
Cellulose 88.0 - 96 91.0 90.8 52
Pectins 0.7 – 1.2 0.53 0.68 12 19.6
Proteins' 1.1 – 1.9 12 30.4
Wax 0.4 – 1.0 0.35 0.42 7 17.4
Ash 0.7 – 1.6 0.12 0,25 14 8.7
Other
Organic
Compound
0.7 to 1.6 3 6.5

47. DISCONTINUOUS
PROCESS CONTINUOUS PROCESS
Kier
Caustic Soda (100%)/gl-1 5-10
Wetting agent/gl-1 0.5-1
Detergent/gl-1 0.5-1
Liquor ratio 3-5:1
Temperature/oC 130
Time/h 4-6
Open width
Atmospheric
Steamer
Caustic Soda
(100%)/%owg
4-10
Wetting agent/%owg 0.1-0.5
Detergent/%owg 0.5-1
Temperature/oC 100
Time/min 30-120

48.  After desizing, the cloth is free from added impurities that has been
added for weaving (starch)
 Inherent impurities like oils, fats, waxes and colouring materials,
remnants of the added matter, dirt/stains are still present
 The oils and fats are hydro-phobic and affect the absorbency of the
cloth
• These resists the penetration of water
• The fabric therefore cannot be dyed or printed

49.  The outer hydrophobic layer has to be removed to make the fabric
absorbent
 The process by which the water-resistant layer is removed is called
‘scouring’
 In cotton textile processing, scouring is also known as kiering, kier-
boiling or boiling out
• Boiling the cloth or yarn in alkaline chemicals
• The boiler or vessel in which this is done is called a “kier” and
hence the terms “kiering” and “kier-boiling”

50.  Objects of “Scouring”
• To remove the ‘natural’ as well as ‘added’ impurities of
essentially hydrophobic character (oils, fats and
waxes) as completely as possible
• To make the goods suitable for removing the natural
colouring matter of the cotton during the subsequent
bleaching operation

51.  Changes taking place during “Scouring”
• The saponifiable oils in it are converted into soaps
• The unsaponifiable oils and waxes it contains are emulsified
• The proteins are hydrolysed into soluble products
• The pectose and pectins are changed into soluble salts of pectic
or metapectic acids
• Mineral matter is dissolved
• Dirt particles are removed and held in a stable form in the kier
liquor

52.  Saponification
• Vegetable oils, animal fats and mineral oils are not soluble in
water
• A vegetable oil is a glyceride of fatty acid
• When oil such as this is heated with a solution of NaOH in water
 Oil splits up into fatty acid and glycerine
 Glycerine dissolves freely in water
 Fatty acid reacts with NaOH to form its sodium salt i.e. soap
which is also soluble in water
• The conversion of glycerides of fatty acids into soaps by using
NaOH is known as “saponification”

53. Vegetable oil + NaOH Glycerine + Fatty Acid
(Soluble in water) (Insoluble in
water)
Fatty Acid + NaOH Soap or Sodium salt of fatty acid
(Soluble in water)
Mechanism of
Scouring

54.  Emulsification
• Waxes present in the fibre cannot be removed by saponification
• They can however be removed from the fibre by converting them
into emulsion, which can be held into kier solution
• An emulsion is a fairly stable mixture of two liquids, which
normally do not mix with each other
• The soap formed by the saponification of oils in the kier acts as
the emulsifying agent
Waxes + Soap Emulsion
(already formed by a
saponification or added)

55.  Scouring processes
• The lime soda process
 Milk of lime is used Ca(OH)2
 The liquor is heated to 1200C at 1.35 Kg/cm2
 Washing to remove soluble impurities
 Steeping the goods in dilute HCl to remove calcium salts
 Followed by washing to remove acid
 Boiling with soda ash to remove the fatty acids
 Washing successively with hot and cold water
 Time consuming process

56. • Caustic soda boil
 Modern processes uses this method
 Impregnating the goods with an alkaline liquor containing
caustic soda, detergent, wetting agent and emulsifying agent
 Treating the liquor to boil at higher than atmospheric pressure
for 6 to 10 hrs
 Draining the scouring liquor and washing with hot water and the
with cold water
 This process is used mainly for cotton textiles

57. • Treatment with soap and soda ash
 Mild temperature is used
 Used for protein and man-made fibres
• Enzyme scouring
 Most updated process
 Only used for cotton textiles

58.  Scouring is done with trichloroethylene
 The fabric is impregnated and passed through
trichloroethylene where the wax and oil dissolves and are
removed
 Other impurities that remain will be degraded and
dissolved during ‘peroxide bleaching’
 Satisfactory in conjunction with peroxide bleaching