defects in dyeing and printing

7/27/2019 Defects in Dyeing and Printing

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DYEING AND PRINTING


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WHAT IS DYEING?

The application of color-producing agents to material, usually fibrous or film,

in order to impart a degree of color permanence demanded by the projectedend use.

Dyeing is accomplished by dissolving or dispersing the colorant in a suitable

vehicle (usually water) and bringing this system into contact with the material

to be dyed.


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CAUSES OF OCCURANCE OF DYEING DEFECTS

Imperfections in dyeing process sometimes occur. They may be due to:

Imperfections in the yarn

Imperfections in the fabric construction

Faulty preparation of the fabric before dyeing

Poor dye selection

Improper dyeing or post dyeing operations


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DYEING DEFECTS

Listed below are the most common dyeing defects:

Barre

Bleeding

Crocking

CSV (center to selvedge variation)

Frosting

Fume fading

Migration

Off shade

Poor fastness to sunlight, perspiration etc.

Shade bar

Shading

Stained fabrics

Stained (unclear) cross dye

Streaked fabrics

tendering


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BARRE:

Description: It is a horizontal shaded

band running across the width of the

fabric.

Cause: It may be caused by variations in

the size of the filling yarn and by

difference in tension of either the filling

or warp yarns of a woven fabric.

Avoidance: It can be avoided with fiber

blending and formula adjustment to thecorrect shade.


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BLEEDING:

Description: It is a dye loss in

water that may color other items

in water.

Cause: Its causes are: improper

dye selection or poor dye fastness,

poor fiber-dye bond, poor

washdown (excess dye on fabric).

Avoidance: It can be avoided by

proper dye selection and a good

post dye washing


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CROCKING:

Description: It is color loss from

rubbing or abrasion.

Cause: it may occur due to

inadequate washing subsequent to

dyeing.


good post dye washing


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CSV (CENTER TO SELVEDGE VARIATION)

Description: It refers to variation of shade

within the same fabric from centre to

selvedge.

Cause: It is caused due to:

o Variation in pH

o Variation in absorbency: Occurs when

uneven desizing takes place.

o Variation in nip pressure

o Combination of dyes used

Avoidance: It can be avoided by checking

and maintaining the right amount of Ph.


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FROSTING:

Description: in this defect, white

areas appear on fabric, seams or

hems due to abrasion.

Cause: it may occur due to poor dyepenetration into fiber. In blends it

may occur due to difference in

abrasion resistant property of the

fibers.

Avoidance: It can be avoided byproper dye selection


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FUME FADING:

Description: it is the fading or hue

shift when exposed to someatmospheric pollutant.

Cause: it occurs due to dye

sensitivity to pollutants.


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MIGRATION:

Description: It is the shifting of color to

the surrounding area or to an adjacent

surface. An e.g. of migration occurs

with some red and white striped

fabrics when the white closest to thered takes on a pinkish cast.

Cause: It occurs due to

poor dye fastness

poor fiber-dye bond

Avoidance: It may be avoided by

proper dye selection


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OFF SHADE:

Description: It refers to a color that

does not exactly match the standard or

prepared sample.

Cause: It may occur due to faulty dye

formulation or application, variation in

dye lot or evaluation of color match

under different lights.

Avoidance: It can be avoided bychecking and maintain the conditions of

the dye bath constant.


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SHADING:

Description: it refers to variation in color

tone either vertically or horizontally

within a piece of fabric, improper

temperature setting, improper speed

setting, improper dosing of dye

chemicals, any defect in RFD (ready for

dyeing).

Cause: it may occur due to uneven

tension on the fabric for e.g. as may

sometimes occur in jig dyeing.

Avoidance: It can be avoided by evenly

tensioning the fabric, and checking and

maintaining the conditions of the dye

bath


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STAINED FABRIC:

Description: it refers to the discolored

cloth accidentally stained during

manufacturing.

Cause: it may occur due to presence of

foreign substance, dirt, grease, oil or

sizing residue on the fabric being dyed.


maintaining a clean dye room.


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STAINED (UNCLEAR) CROSS DYE:

Description: it occurs in a cross dyed fabric

of white and color. The dye of the colored

yarns may stain the white one.

Cause: this is usually due to poor dye

selection and fastness.

Avoidance: It can be avoided by proper

dye selection.


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STREAKED FABRIC:

Description: it indicates either a stain

or uneven dyeing.

Cause: it is caused due to folds in thefabric during dyeing process.

Avoidance: It can be avoided by giving

good pre-dyeing treatments, proper

dye selection and maintaining proper

fabric tension


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TENDERING:

Description: in this, fabric becomes weak

or sensitive to abrasion.

Cause: it occurs due to poor dye-fiber

interaction.

Avoidance: It can be avoided by thoroughly

oxidizing the dye within the fiber or after

treating the fabric to neutralize the

chemical causing tendering.


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TAILING :

Definition: When the dyed fabric is

hung on clothes line, most of the dye

tends to accumulate towards the bottom

edges of the hung fabric

Causes: It may be caused due to the

improper absorption of the dye by the

fibers.

Avoidance: It can be avoided by proper

selection of dye and fixing agents.


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DETECTION OF DYEING DEFECTS


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VISUAL INSPECTION

It is the process in which manual

inspection is done for the defects like

stains, streaks and other defects.

The equipments employed are the

inspection table and suitable chemical

according to the type of dye & fabric to

remove the stain & other defects


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SPECTROPHOTOMETER

Spectrophotometer is the instruments

that measure reflectance from, or the

transmittance through, materials as

function of the wavelength.

This instrument can easily detect a

shade variation by detecting the difference

in the wavelength of the reflected light.


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COLORIMETER

This instrument is designed to measure

the depth of the color or the dye.

It is utilized to detect the defect where the

dye has not being taken up by the fiber or

where the shade or lighter is darker than what

required


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WHAT IS PRINTING?

Textile printing is a general name for all woven fabrics and the art of ornamenting such

fabrics by printing on designs or patterns in color.

The application of colorant in definite, repeated patterns to fabric, yarn or sliver.

The different methods of printing include hand,screen, automatic screen, rotary

screen, roller and heat transfer.

Each method can be used to print one or more print types.

These include direct, discharge and resist prints.


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PRINTING DEFECTS

Listed below are the most common printing defects:

Outfitting of Design

Pin Holes

Colour Fastness

Sharpness of print

Creaser Problem

Width variation

Water Mark

Pigment Colour Bleeding

Reactive colour bleeding

Oil Dropping

Continuous or periodic spots

Fails on the synchronism of the

printing cylinders

Lack of dye due to block pipe or

empty container

Defective pigment condition in one

or more of the used dyes.


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OUTFITTING OF DESIGN

Origin : Exposing problem

Machine Gear box movement

Variation of speed from cloth and blanket

Remedy: Before Delivery the screen should be checked

Before starting the machine gear box is to be checked


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PIN HOLES

Origin: From screen and Dyes Chemicals

Remedy: Before Printing the holes need to be closed by brush and

liquid (Chemical Paint)


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COLOUR FASTNESS

Origin: Colour Chemical standards

Remedy : Use of standard colour and chemical


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SHARPNESS OF PRINT

Origin: Design

Remedy: Paste and screen problem

Paste to be thick , screen thickness needs to be checked


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CREASER PROBLEM

Origin : Printing damageRemedy : Required width to be maintained on the stenter

Printing guider should function while running the machine


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WIDTH VARIATION

Origin : Selvedge damage of cloth

Remedy : Grey cloth stitch as per required width.

Photocell should function while batching the cloth from senter


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WATER MARK

Origin : Blankets

Remedy : Check and clean blanket and wash

Clean spray pipe holes and remove flupps with brush


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PIGMENT COLOUR BLEEDING

Origin : Chemical problem

Remedy : Use good quality binder and check in lab


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REACTIVE COLOUR BLEEDING

Origin : Water Problem and steaming problem

Remedy : Colour to be developed in required steam pressure

Use soft water in washing machine


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OIL DROPPING

Origin : Low temperature, unclean chamber and iron rod

Remedy : Drier temperature must be 140 C

Wash and clean the conveyor


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CONTINUOUS OR PERIODIC SPOTS

The development of small adherences of threads or cloth shreds, breaks or

unevenness on the fibre, tint drops, etc can give raise to repetitive stains.

FAILS ON THE SYNCHRONISM OF THE PRINTING CYLINDERS

When a slight phase offset appers among the cylinders, the printed areas can

overlap or get apart, giving rise to objectionable visual appearance of the result.


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LACK OF DYE DUE TO BLOCKED PIPE OR EMPTY CONTAINER

If the dye supply to a cylinder decreases the whole or a part of the design will lack the

pattern corresponding to that color. This defect appears in cases where the printing

pattern includes small areas for certain colors, which can pass unnoticed ruining 100 of

meters of fabric

DEFECTIVE PIGMENT CONDITION IN ONE OR MORE OF THE USED DYES

The colour achieved at the printing does not match exactly the one required by customer

order.


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