Dyes – Application types

Direct Dyes
• Also called as Substantive dyes

• Water soluble and Least expensive;

• Easy to apply, can be applied directly without

pretreatment, fixing agents are not required.

• The colors of most direct dyes are duller than

those provided by fiber reactive dyes

• Wide range of colors and shades

• Used as back ground color for discharge

printing

• Wash fastness is poor but a little more

lightfast.
 DIRECT DYES on Cotton AFTER- TREATMENT
 Cellulosic substrate + dye bath at 49°C ► Cationic fixing agent (e.g. 1-2% o.w.f.
and dyeing is continued for 15- 20 of the fixing agent for material
minutes. dyeing with 1% of a direct dye), and
a small amount of acetic acid (pH of
bath: 5-6).
 Then common salt or glauber’s salt in
the solid form is added portion- wise ► Treated at 49°-54°C for 15-20
(1/8, 1/8, 1/4, and1/2 of the total minutes.
amount), over a period of 45-60 minutes
► Rinsed with cold water and dried.
 Salt used 5-25%, depending on the depth ► The light-fastness of some direct
of shade, liquor ratio, and the type of dyes can be improved by an after-
direct dyes used. treatment with copper sulfate.
► Small improvements of both light
 If the shade is satisfactory, the dyed and wash-fastness in after-treatment
material is then rinsed with cold water. are mixtures of copper sulfate and a
cationic fixing agent.

 At this stage an after – treatment may

follow to improve the wash – fastness of
the dyes.
 Sulphur Dyes
• These dyes contain Sulphur atom in
their molecules.

• Sulphur dyes are insoluble in water

• Suitable for the MMF and Natural

Cellulosic fibers

• Dull shades, predominantly navy,

black, brown

• Excellent fastness to light and washing

• Relatively low cost for dark colors.

• Poor fastness to chlorine bleach

 Application of Sulfur dyes for cellulosics

The dye-bath is prepared by diluting the Sulfur

Dye with the proper amount of water.

A small amount of sodium polysulfide (e.g. 1-2 %

o.w.f.) and a similar amount of a sequestering
agent are added, and the fibers are introduced
into the dye-bath at 50°C.

Sodium chloride (20-30%) o.w.f.) is added portion

–wise (e.g. 1/8, 1/8, 1/4, and 1/2 of the total
amount) over a period of 20 min., while the
temperature is gradually raised to the maximum
dyeing temperature, usually in the range of 60°-
82°C.

Dyeing continues at this temperature for about

30 min.

The fibers are then rinsed well with warm and

hot water, oxidized, rinsed, soaped at 82°C,
rinsed with a mild alkali solution, and dried.
 Reactive Dyes
• More than 75% of cotton dyeing are produced using
Reactive dyes only

• Dye molecules react chemically with the fiber polymers to

form a covalent bond.

• The dyestuff becomes a part of the fibre and is much less

likely to be removed by washing.

• Suitable for MMF and Natural Cellulose and Protein fibers.

• Bright Shades.

• Easy to obtain level dyeing;

• Excessive time required for dyeing process.

• Very good fastness to washing; Good-very good fastness

to light;

• Good fastness to dry cleaning, perspiration, crocking;

• Poor fastness to chlorine bleaching

• Procion and Remazol are the popular reactive dyes in the

market
 REACTIVE DYES on cotton
Applications of reactive dyes by batch dyeing consist of three stages:

1. Exhaustion

2. Fixation, and

3. After- scouring
 The following is a typical procedure for
exhaust dyeing at a high temperature:

 The dye bath temperature is set at 50°C and

the pre-dissolved reactive dyes are added.

 Then the substrate is placed into the dye-

bath and the temperature is raised at 1°C per
min to 80°C (about 30 min).

 During this time the salt (e.g. 100% o.w.f.,

depending on liquor ratio and depth of shade)
is added portion-wise.

 Dyeing continues at 80°C for an additional 15

min., after which sodium carbonate is, added
over 15 min.

 The dyeing machine is run at 80°C for 45-75

min., during which fixation is completed.

 The dyed material is given two more rinses,

first with warm water followed by cold water,
and then dried.
 Cold and Hot brand Reactive dyes

Cold Brand Reactive Dyes Hot Brand Reactive Dyes

• Dichloro tri-azine dyes = Monochloro tri-azine dyes

• More dye affinity = Relatively less dye affinity

• More salt quantity is required = Compare to cold brand reactive

dyes less salt is required

• Dyed at Room temperature = Dyed at 80 to 85° C

• Ex.Procion fibre reactive dyes = Ex.Remazol (vinyl sulphone dyes)

fibre reactive dyes
 Vat Dyes
• Vat dyeing means dyeing in a bucket or vat.

• Water Insoluble and incapable of dyeing

fibers directly.

• Both cotton and wool, as well as other

fibers, can be dyed with vat dyes

• Vat dyes have excellent wash and light

fastness properties.

• It is usually very bright and will hold up

better when bleached than most other
dyes.

• Dyes are costly and dyeing procedure

demands addition of costly chemicals,
which makes the process still costlier.
APPLICATION OF VAT DYES FOR CELLULOSICS
The conventional exhaust method of vat dyes consists the following major
steps:

Reduction (vatting)

Dyeing

Oxidation

Soap at boil
 Reduction (Vatting)
► At this stage, the vat dye is converted into its
soluble form.

► The dye is first mixed with the proper amount of

sodium hydroxide.

► Then the reducing agent is added, and the

temperature is raised to the recommended
temperature(The reducing agents most
commonly used are sodium hydro-sulphite
(Na2S2O4) and thio-urea-dioxide)

► The use of soft water throughout the dyeing

process is must with vat dyes, since the soluble
leuco salts will form insoluble salts with calcium
or magnesium ions as well with transition metals.

► Therefore, in addition to using soft water, it is

common to add sequestering agents* such as
EDTA to the dye bath.
*A substance that removes a metal ion from a solution system by forming a complex ion
Vat Dyeing Procedure
The scoured material is inserted in the dye-
bath and the temperature is gradually raised
to the dyeing temperature (27°C to 60°C)
depending on the type of dyes used.

Dyeing continues for the proper amount of

time and salt may be added to assist in
exhaustion.

Since atmospheric oxygen reacts with the

reducing agent as well as with the reduced vat
dyes, additional amounts of the reducing
agent and the base are added during the
dyeing stage.

The dye-bath is checked occasionally to

ensure that the pH of the bath is sufficiently
basic (phenolphthalein paper should turn red),
and that a sufficient amount of the reducing
agent is present in the dye-bath (yellow vat
testing should turn blue).
 Oxidation:

Before oxidation, the material is rinsed

to remove residues of sodium
hydroxide and reducing agent.

Common oxidizing agents used today

are hydrogen peroxide and sodium
perborate.

When using hydrogen peroxide, high

concentrations of alkali must be
avoided to prevent damages to fibers.
 Soap at the boil:
This step consists of treating the dyed material with soap at or near the
boil for 10-20 min.

Soap at the boil increases the wash fastness of the dyes and yields their
final shade.

The dyeing procedure is then completed by rinsing with hot and cold
water.
 Application conditions for Various Types of Vat Dyes

(Approximate values for dyeing medium shades at liquor ratio of 1:10)

TYPE IN IW IK

  method 1 method 2 method 3

Reduction 60°C 49-54°C 38-49°C

Temp
Dyeing Temp 60°C 44°-49°C 21°-26°C

NaOH 6-9 g/l 3-5 g/l 2.5-4 g/l

Hydrosulphite 6-9 g/l 4-6 g/l 3-4.5 g/l

Salt none 7.5-15 g/l 10-20 g/l

IN – normal procedure
IW – warm temperature
IK – cold temperature
 SOLUBLE VAT DYES

 Already in the reduced soluble from and will not oxidize

by merely exposing them to the air.

 Only limited number of shades

 Cannot give deep shades.

 More expensive than vat dyes.

 Used for cotton, linen, rayon, cotton blends, (including

embroidery yarns and sewing threads) polyester blends,
wool and silk blends through single bath in pale to
medium shade.

 Good fastness to light and washing.

 Azoic Dyes
• Azoic dyes contain an Azo group.

• It is suitable for MMF and Natural

Cellulose fibers such as Cotton,
Viscose, etc

• Bright Shades, mostly deep Red,

Yellow, Orange, etc.

• Light Fastness Fair to Good.

• Washing Fastness Good to Excellent.

• Heavy shades may have poor fastness

to Crocking.
 AZOIC DYE ON COTTON
• Application of azoic dyes on cotton material consists 3 steps:

1. Naphtholation
2. Coupling or Diazotisation
3. After-treatment
 Naphtholation
 : with Turkey
Paste the Naphthol
red oil (TRO) or sulfonated oil,
and a small amount of water.

 Raise the temperature to 85°C.

 Add the required amount of

alkali in the form of a
concentrated solution.

 Continue to heat for a few min.,

while stirring.

 And raise temperature to the

boil if needed until a clear
solution is obtained.
Intermediate step- hydro-extraction

 The purpose of this step is to remove, from the fiber’s surface, as much of
the naphtholate solution as possible in order to avoid crocking problems.

 This is done by centrifuging, squeezing, vacuum extraction, or other

means of hydro-extraction
Coupling :
 The naphtholated substrate is
immersed in the diazonium salt
solution at room temperature for
15-20 min., during which time the
coupling reaction is completed.

 For the coupling to take place at a

desirable rate, without affecting the
stability of the naphtholate or the
diazonium salt, a specific pH must
be maintained for each
combination used; usually it is in
the range of pH 5-7.

 Many times a mixture of acetic

acid and sodium acetate is added
to the diazonium salt solution to
act as a buffer and maintain a pH of
about 5.
 After-treatment:

At this stage the dyed substrate undergoes a vigorous rinsing in order to:

1. Remove unreacted materials,

2. Remove dye attached to fibers’ surface, and

3. Improve wash-fastness and yield the final shade.

 Disperse Dyes
• There are three major reasons for the poor
dye-ability of polyester

• High fiber crystallinity

• High Hydrophobic nature
• Absence of chemically reactive
groups in the polymer.

• Used for dyeing polyester.

• Insoluble in water
• More likely to cause allergies than other
textiles dyes.
• Acidic pH is required
• Dyeing is carried out at HTHP
• Wash Fastness varies with the fibers.
• Fastness to Crocking is Good to Excellent.
• Light Fastness is Fair to Good
 DISPERSE DYE ON POLYESTER
• Dyeing of polyester using disperse dyes can be done by using the following
methods:

(1) Atmospheric dyeing with dye-carriers.

(2) High temperature & High pressure dyeing.
(3) Continuous dyeing by the thermosol process.
 ATMOSPHERIC DYEING WITH DYE-CARRIERS
• Certain hydro carbons, phenols, amino acids, amides, alcohols,
esters, ketones, nitriles etc accelerate the rate of dyeing of PET fibres
from aqueous medium at the boil

• These dyeing assistants are called carriers, which alter the dispersion
properties of the dyes and the physical characteristics of the fibre so
that more of dyestuff can be transferred from dye bath to fibre

• They swell the fibres at boil to relax the spaces between inner
molecular structures of the fibre to accommodate the dye particles.

• The carrier is added slowly during the dyeing process because if it is

added at once, the dyestuff may rush on to the material.

• Only a small percentage of the polyester fibres in the use is currently

dyed by this method, since it requires the use of large amounts of the
undesirable dye-carriers.
Factors in selecting a carrier

• High carrier efficiency

• Low cost
• Little or no effect on light fastness
• Absence of unpleasant odor
• Non toxicity
• No degradation or discoloration of fibre
• Ease of removal after dyeing
• High stability under dyeing condition
• Compatibility with dyestuff
• Ease of dispersion in dye bath
• Low volatility
• Uniform absorption by fibre
 HTHP - DYEING
• Dyeing at temperature as high as 135°C
(275°F) is possible with new dyeing
equipment that can withstand high
pressures.

• Under these conditions better diffusion

and dye-fastness are obtained without
using dye-carriers.

Advantages:

• Good overall fastness (wash fastness,

crocking, etc.).
• Good leveling properties.
• Eliminate completely the dye-carriers
• Possibility wider range of disperse dyes
DYEING PROCEDURE
• The required amount of hot water, dispersing agents (ammonium
acetate) and auxiliaries are taken in a separate bath.

• The pH of the bath is maintained at 5.5 to 6.5, with the help of acetic
acid.

• The scoured material is entered in the bath.

• The material is worked in this solution for 20 minutes at 60°C.

• The required amount of dye liquor is added.

• The temperature is raised to 135°C.

• Dyeing is continued at this temperature for 45 to 60 minutes.

• After dyeing, the material is taken out and given cold wash.

• After treatment is given with soap(3 g/l), soda ash(1 g/l) at 50°C for
10 minutes.

• Again washed with cold water.

 Thermosol Dyeing
• Method of dyeing PET, Nylon and Orlon without using carriers, by duPont

• Since the thermoplastic fibres when heated to a high temperature, they soften, their internal
structure is opened up, facilitating the entry of disperse dye molecules in the fibre

• This plasticizing effect of heat on the fibres is responsible for rapid rate of diffusion of dye
into the fibre, requiring from only a few seconds to one minute at a sufficiently high
temperature
 DYEING PROCESS
• The application is carried out continuously and consists of padding the polyester fabric with disperse dyes.

• The padding bath contains in addition to the dyes, acetic acid (pH 4.5-5.5 ) and a wetting agent(1-3 g/l ).

• Since the application medium is water, a drying step is required, thereby leaving only the dye on the surface of fibres

• Drying and then placing the fabric in a curing oven at 200-210°C for less than one minute.

• During which the dyes diffuses and becomes fast to remove even by the strongest laundering procedure

• Followed by scouring -to remove the assistants used in padding and to remove unfixed, residual dyes

• Advantage – large yardages can be used as it is continuous, no carrier used, excellent dye utilization(90%), open
width so no creases
 Acid Dyes
• Water soluble anionic dyes
• Used for silk, wool, nylon & modified acrylic fibers
• Bright Colors.
• Non fast to washing.
• Excellent Fastness to Dry Cleaning

Process

• Material is run in dye bath for 10 minutes at 40c.

• Then temperature is raised to boil in 30 – 40

mins.

• Dyeing is continued at boil for another 40 -60

mins to complete exhaustion and fixation.

• Thorough washing in hot and cold water removes

unfixed dyes.
ACID DYE ON WOOL
• The dye – bath is prepared at 49°C, in addition to
the acid dyes, an acid (e.g. 2% H2SO4 o.w.f) or
other acidic chemicals are added as required, to
obtain the proper pH of the bath.

• Sodium sulfate (glauber salt: Na2SO4, 10% o.w.f) or

other dyeing assistants are added as leveling
agents.

• The dyeing machine is run for 5-10 min., after

which the wetted material (raw stock, yarn, or
fabric) is inserted.

• The dye bath temperature is gradually raised (1°

per min) to the boil while agitating the material
and circulating the dye solution through the
material.

• Dyeing is carried out for 40-60 min., after which

the dyed material is rinsed with cold water and
dried.
 ACID DYE ON SILK
• Most widely used dyes on silk

• Brilliancy of shades and good color fastness performance

with simplicity of application.

• For dyeing silk, usually degumming liquor (boiled-off

liquor) is used with water.

• It acts as leveling agent and keeps the silk soft and

lustrous.

• The dye bath is set with 100 - 500 ml boiled-off liquor

and made slightly acidic with acetic or formic acid.

• The material is entered at 50°C and run for 15 minutes

before adding the previously dissolved dyestuff.

• The dyestuff is added in portion wise and the

temperature of the dye bath is raised gradually to 90°C
and the bath is maintained this temperature for 30 -60
minutes until the dyeing is completed.

• After dyeing, the silk is rinsed and brightened by working

in a dilute solution of acetic acid, squeezed well and
dried.
 ACID DYE ON NYLON
• The required amount of dye stuff is taken in a separate
bath with a little amount of wetting agent is added for
pasting it and mixed with hot water.

• The required amount of hot water is taken in a separate

bath.

• Ammonium acetate (3%) and phenol (3%) are added as

carriers and dye liquor is added.

• The wet material is entered in the dye bath.

• The temperature is slowly raised.

• Dyeing is continued for 20 minutes.

• 3% of acetic acid is added as exhausting agent.

• Dyeing is continued at boiling temperature for 45 to 60

minutes.

• Finally the material is taken out and given cold wash.

Acid Milling Dyes
• Further development of acid dyes
• Having super wet-fastness, good light fastness, and less tendency to bleed

Acid Pre-Metallized dyes

• Another outgrowth of acid dyes
• Having two molecules of chromium bound to the dye
• Requires strong acid bath to dye
• Presence of metal improves colorfastness, greater than acid/acid milling
• Used on wool, nylon and acrylics

Neutral Pre-Metallized dyes

• Have one molecule of metal, usually chromium, bound to two molecules
of dyes resulting in improved fastness properties
• No bright shades as acid dyes
• Used on wool, silk, nylon, acrylics
 Basic Dyes
• Very bright

• Good wash fastness on

acrylic.

• Very Poor fastness to

washing for Cellulosic and
Protein

• Water-soluble and contains

cationic group

• Characterized by Brilliance
and Intense hue.
 BASIC DYE ON ACRYLIC
• Dye bath prepared with auxillaries at 50°C.

• Acetic acid added for pH of 4.5-5 and sodium sulfate (5-10%

o.w.f) and a cationic retarder (1-2% o.w.f) are added as leveling
agents.

• The fabric is entered and the bath is run for 5 minutes.

• Then the dissolved dyes are added slowly over a period of 10

minutes.

• After which the temperature is raised at 1°C per minute, to just

below the glass transition temperature (anywhere between 68-
85°C) of the fibre.

• Dyeing temperature is kept at this point for 15 minutes, after

which it is raised to the boil.

• Then the dyeing continues at the boil for about 1 hour.

• When proper shade is obtained, the dye bath is cooled very

slowly to about 10°C below the glass transition temperature (to
avoid the formation of creases), and then dropped.

• The dyeing is completed by rinsing.

Dyeing of Silk with Basic Dyes

Receipe:

● Basic Dyes - x %
● Acetic Acid - 1 – 2 %

● Dye bath is set with acetic acid and the material is entered at the cold
condition.
● Dyes are dissolved separately using acetic acid.
● The dissolved dye is added to the dye bath in three instalments while the
temperature is being raised from cold to 80c
● Dyeing is continued at 80c for 40-60 min more.
● Dyed material is washed thoroughly to remove unfixed dyes.
● To improve the wet fastness, the dyed goods are worked in a bath containing
1% tannic acid at 60c for 20 min.
Cationic Dyes
• Brilliant shades with excellent fastness
properties on the acrylic fiber

• 100% Acrylic fiber has no affinity for any dyes.

• The addition of a small proportion (up to 15%)

of anionic monomer has increased the dye-
ability to the acceptable level.

• Acrylic can also be dyed with disperse dye.

Dyeing of Acrylic fiber with Cationic Dyes

Recipe:
● Basic Dye - x %
● Retarder - 1-2%
● Sodium acetate and acetic acid - Buffer
● Temperature - 95c
Solvent Dyes
• Soluble in an organic solvent.

• It’s a alternative method, as the use of water and its

disposal in a non polluting form has become more
expensive.

• Ammonia, perchloro ethylene, trichloro benzene have

been found to be superior dye vehicles, penetrate better
almost wide variety of MMF

• Also energy saving, cost effective, exhausted solvents

are recoverable, non polluting etc

• To improve further dye penetration, a machine called

Pulsar was invented in Italy, which utilizes sets of
continuous rapid impulses in the solvent medium which
hits both sides of fabric in rthymic alternation

• Material is moved by gravity and vibration of pulsators

• Tensions, stretch and surface distortions are eliminated

• Both open width and tubular fabrics can be dyed

 Mordant Dyes
• Dyes which require a mordant* in their
application and which upon combination
with the mordant deposit insoluble color
on the substrate.

• The mordant substances include such

acids as tannic acid, bark extracts, oleic
and stearic acids, and TRO; and metallic
substances such as various combinations
or soluble salts of chromium, aluminum,
iron, copper, and tin.

• Suitable for Wool

• Relatively Dull Colors

• Good to Excellent Fastness to Light and

Wash.
*a substance, typically an inorganic oxide, that combines with a dye
or stain and thereby fixes it in a material
DYEING OF BLENDS
 Polyester Cellulose Blends

• Disperse dyes for the polyester component.

• Cellulose portion with practically all classes of dyes

• Dyeing with premixed disperse and vat dyes is especially easy.

• The mixed dyes can be applied in a single bath by the exhaustion or

continuous process.

• The dyes are formulated in such a way that the same shade is obtained on
both fibers, which facilitates shade matching
 POLYESTER/COTTON BLENDS
• Three methods can be applied for 2. Single bath method
dyeing polyester/cotton blends:
3. Continuous dyeing
• In single bath, polyester and
(1) Two bath method cotton dyeing can be done in two
steps. • Disperse and reactive dyes are
padded in two padding
• Polyester is dyed using disperse
mangles continuously.
dye in the first bath. • Initially, the dye bath is prepared
using disperse dyes.
• Fabric is treated at very high
• A reduction clearing is applied speed (100 yards per minute).
• Temperature is raised to dye the
for removing unfixed disperse polyester.
dye. • Dwelling chamber for dye
fixation
• After dyeing polyester, the
• Then cotton is dyed with temperature is dropped for dyeing
cotton with reactive dye. • Reduction clearing done in
reactive or vat dye in the
between the padding
second bath
mangles.
• Reduction clearing cannot be
used.
• Best method for union dyeing
of cotton/polyester blends. • Saves time and energy.

• • Both the fibers can be dyed

Chances of stain are minimized.
simultaneously in a single dye
bath using proper dyes and
• Can also be used for cross maintaining proper temperature.
dyeing.
Polyester Wool Blends
• Disperse dyes for the Polyester
component

• Acid or metal-complex dyes for the

wool.

• Wool cannot be dyed at the high

temperatures

• Disperse dyes can soil wool to a

great extent.

• The dyeing time should also be as

short as possible so that the wool is
not damaged.
 Dyeing of Polyester-Viscose
• The traditional dyeing process is • Lenzing has developed a new cationized
complex as a two-step procedure is viscose fiber dubbed “Rainbow”, facilitating
required. the dyeing procedure and drastically
reducing time consumption
• Using the “Rainbow fiber”, the fabric
can be dyed in a single step at low pH • Rainbow fibers can be dyed at 130°C using
without addition of salt, requiring only direct and metal complex dyes without
one rinsing step and achieving a very addition of salt giving fastness properties
high degree of dye bath exhaustion. comparable to reactive dyeing at 60°C.

• Rainbow fibers have the same physical • With Rainbow, the time needed for the
fiber properties (tenacity, water dyeing process could be reduced by up to
retention, etc.) as viscose fibers, except 70%.
dyeing properties.
• Further advantages of Rainbow are the
• This unique combination of properties reduced water and wastewater quantities
has been realized by incorporation of a (by 65 %) and reduced energy costs (by 65
cationic polymer into the viscose %) per kilogram of dyed fabric.
spinning dope, thus achieving
permanent modification
Dyeing of Cotton-Viscose
• Very difficult to dye in to a solid shade.

• Viscose has a very high affinity towards

reactive dyes when compared to cotton
cellulose. 

• If one tries to dye a solid shade out of

this blend, he/she would certainly end
up in dyeing a contrast shade, due to
differential dye pick up.

• A simple pad-dry-cure pretreatment with

a cationic dye fixing agent, with say 4~5
gpl, would make the cotton cationized.

• This cationized cotton/viscose blend,

when dyed with a reactive dyestuff
would result in a good solid shade.
DYEING OF KNITS
• The tensions in wet processing and
apparel manufacturing can render a knit
unacceptable with respect to weight,
width and shrinkage

• In the purest form, linear tension in

processing increases (stretches) the fabric
length and decreases the width

• Use of driven reels is recommended for

knits because they help move the fabric
at a lower tension

• Care must be taken to prevent scuffing or

abrading of the fabrics by the reels

• Speed of the reel should be controlled so

that the fabric does not slip on the reel
• Loading of the fabric into the jet should be
done with a lower speed than the dyeing
speed to allow proper wetting and packing
of the fabric.

• The goal is to let the goods relax in the

width and the loops in the fabric to
reorient them without forming creases,
folds, crows feet, and rope marks.

• It is recommended that the jet be charged

with surfactant and lubricant before the
fabric is loaded.

• After the fabric is fully loaded, the speed

of the fabric can be optimized for uniform
dyeing

• The depth of the chamber is important

because a chamber that is too deep will
result in forward and backward tumbling
of the fabric, which will result in increased
tangling and severe linear tensions in the
fabric. 
• Unloading from the jet after
processing is also an important
consideration in preventing
subsequent stretching during the next
stage of extraction.

• In most cases, single jersey fabrics

constructed with a single yarn will
torque during wet processing and
accentuate the twisting.

• This twisted rope must be removed

before the fabric is extracted.

• De-twisting is usually performed at

the extractor or just before extraction
and can be a source of high tension.