Pretreatment Process of Textile Materials

Pretreatment:
Pre-treatment means any treatment, which is done before actual (dyeing and printing) process. Pretreatment processes include dsizing, scouring, and bleaching which make subsequent dyeing and softening processes easy. Uneven desizing, scouring, and bleaching in the pretreatment processes might cause drastic deterioration in the qualities of processed products, such as uneven dyeing and decrease in fastness.

Process pretreatment of textile is all mechanic and chemical process to textile materials both for is made from natural and synthetic fiber before dyeing, printing and finishing process ,with purpose the process is fluently better and the result can which as expected.

Object of Pretreatment:

• To Convert fabric from hydrophobic to hydrophilic state.
• To remove dust, dirt etc from the fabric.
• To achieve the degree of desire whiteness.

Pretreatment Process of Textile Materials:
Cellulosic fibers, whether they are natural or regenerated need some form of treatment to make them suitable for dyeing or finishing. This treatment, which removes natural or added impurities, is called preparation pretreatment. It can be carried out on loose fibers, yarns or fabrics.

Unless the fibre is uniform in whiteness, absorbency and chemical composition and has law levels of impurities it is unlikely that it will take up dye or finish in a uniform way or to the maximum extent possible. The prepared fabrics must have ‘fitness for purpose’. For example, a fabric to be given a water-repellent finish must be free from residual surfactant. Fibers used for medicinal end uses must have a law ash content.

All such requirements must be met against economic constraints relating to the costs of water, labour, plant, chemicals and energy. The first, water, is particularly important. Not only can the purity of the water affect many of the requirements but the volume and the environmental impact of effluent can, and is, adding increasingly to the cost per kilogram of textile produced. The effluent with the highest biological/chemical oxygen demand stems from pretreatment.

Successful preparation depends on four factors:

• The level and type of impurities present.
• The chemicals used in the various stages of preparation.
• The water supply.
• The type of machinery used. 

 

Garments Trimmings | Garments Accessories | Marker | Interlining | Garment Pattern | Fabric Spreading | Lining

Garments Trimmings:

Those accessories which are used in sewing section are called trimmings.

Garments Trimmings

Garments Accessories:
Fabric is the basic material in garment manufacturing. Except fabric, the other materials are known as accessories. For shirt making there are some accessories are commonly used.

List of Garment Accessories:

1. Thread
2. Zipper
3. Interlining
4. Button for example: Snap button, Plastic button, .Metal button.
5. Label: Main label , Size Label, Wash care label
6. Motif: Leather, Plastic, batchMetal
7. Pocketing fabric
8. Lining
9. Velcro
10. Elastic
11. Cord
12. Ribbon
13. Toggles
14. Rivet
15. Collar bone.

Finishing Accessories:
There are some finishing accessories:

1. Hang tag
2. Price tag
3. Plastic/ poly bag
4. Tissue paper
5. Carton
6. Scotch tape
7. PP belt
8. Tag pin
9. Plastic clip
10. Stiker
11. Butterfly
12. Collar insert
13. Back board
14. Necks insert

Button:
In clothing and fashion design, a button is a small disc, typically round, object usually attached to an article of clothing in order to secure an opening, or for ornamentation. Functional buttons work by slipping the button through a fabric or thread loop, or by sliding the button through a reinforced slit called a buttonhole.

Buttons may be manufactured from an extremely wide range of materials, including natural materials such as antler, bone, horn, ivory, shell, vegetable ivory, and wood; or synthetics such as celluloid, glass, metal, bakelite and plastic.

Hard plastic is by far the most common material for newly manufactured buttons; the other materials tend to occur only in premium apparel.

Zipper:
A zipper or zip fastener) is a popular device for temporarily joining two edges of fabric. It is used in clothing (e.g. jackets and jeans), luggage and other bags, sporting goods, camping gear (e.g., tents and sleeping bags), and other daily use items.

Interlining:
Interlining is a layer of flannel fabric sewn in between the face fabric and the standard lining. Interlining provides insulation and also adds a luxurious weight and softness, improves the drape of the fabric, and protects fragile fabrics. It is a popular choice with silk draperies.Depending on the application, interlining materials can be woven, knitted, or created by fusing fibers together. Silk, wool, and artificial fibers with good insulating qualities are common choices for interlining.

Garment Pattern:
The individual par of a garment which is shaped by hard paper is called pattern.

Working Pattern:
The patterns set which is used for sample making are called Working Pattern.

Marker:
Marker is a large thin paper which contains shape of required pattern pieces or a particular style of garments.

Fabric Spreading:
Spreading means smooth lying out of fabrics as per marker length and width.

Fabric Cutting:
Cutting is the process by which we can cut fabrics as per marker dimension with the help of knife.

Bespoke Garments:
Bespoke Garments are made on the basis of individual clients and according to the individual’s size and requirement.

Ready to Wear Garments:
Ready to wear garments is made on the basis of target common groups, according to size charts, derived from statistical analysis.

Lining:
Lining is one kind of trimmings which is used underside of garments and use in next to skin.

Sewing Thread Winding System | Different Types Winding | Precision winding | Parallel winding

A transformer winding in which all the turns are arranged on a bobbin instead of in the form of a disk. Generally used for the high-voltage windings of small transformers.

Different types of Sewing Thread winding system

Precision winding: 

• Constant winding ratio

• Winding angle reduces with increasing diameter

• No pattern areas

• Good off-winding characteristics

• High package density

Step precision or digicone winding:

• Almost constant winding angle

• The wind ratio is reduced in steps

• Combines the advantage of random and precision winding

• No pattern areas

• Higher consistent package density

• Perfect unwinding characteristics

• Straight sided packages

Random winding: 

• Winding angle is kept constant since the winding ratio reduces with increasing diameter

• Stable packages

• Even density

Pineapple winding:

• Winding traverse reduces to produce packages with tapered edges

• Required for filament winding operations

• All three types of winding applicable

Parallel winding:

• Very high package density

• Thread vertical to package axis

• Relatively short lengths of thread

• Suitable for side unwinding

• No pattern areas 5,6

Ball winding:

• Very easy unwinding 

• Winding takes place in 4 stages:

1. Rough base winding

2. Form winding

3. Surface layer winding

4. Circumferencial winding

Skein winding:

• Easy unwinding

• Very small parallel strand of soft twisted thread.

Uses of Sewing Threads, Embroidery Thread | Necessities of Sewing Threads

Sewing thread is a flexible, small diameter yarn or strand usually treated with a surface coating, lubricant or both, intended to be used to stitch one or more pieces of material or an object to a material. It may be defined as smooth, evenly spun, hard-twisted ply yarn, treated by a special finishingprocess to make it resistant to stresses in its passage through the eye of a needle and through material involved in seaming and stitching operations.

Applications of sewing threads

Approximately 80% of all sewing threads produced are used by the clothing industries. sewing, embroidery, applique and serging thread that needlecraft hobbyists and professionals need. We carry product lines from Aurifil, Floriani, Gutermann, Isacord, Mettler, Presencia, Robison Anton, Signature, Superior, Wonderfil, YLI, and more. We also carry the entire line of Floriani Embroidery Stabilizers, and a wide selection of quilting patterns and sewing notions.

Importance of Sewing Threads

The sewing thread is of considerable importance, playing a major role in retaining the fabric appearance, look, and life of the garment in the long run, even though it usually represents much less than 1% by mass of a garment. 

Nowadays, a numerous variety of sewing threads are available in the market due to diverse demands from the sewing industry, increasing use of different types of fibres in the garment industry and expanding application of textile materials in various fields like apparels, technical applications as well. Better understanding of the sewing process and its requirements as obtained through studies by modern instrumentation techniques has also greatly contributed to the development of new threads. It is also very much required and appreciable to have different types of sewing threads, which can suit various applications, since various end-uses demand specific property requirements.

It is beyond anybody’s doubt that the success of garment manufacturing process mainly depends upon the operation of sewing, though a very better quality of fabric is selected for the garment manufacturing process. Again, the sewing threads play a vital role in the success of sewing operation, since a wrong thread may ruin a very high quality fabric and even a best sewing machine used for the sewing, and the whole process will fail. It can add to waste of both time and money. Hence, it is very much imperative to select a right type of sewing thread which can suit one’s requirements exactly. This is possible by the correct understanding of the type of fibre used to manufacture, manufacturing processing sequence & properties of different types of sewing threads existing on earth, which was touched upon in this technical article to a greater extent.

Sewing Threads | Different Types of Sewing Threads

Sewing Threads

Sewing threads can make or mar a garments, and hence a through understanding of their processing and properties is vital for the industry to choose the right type of the threads. According to the definition given by ASTM, sewing thread is a flexible, small diameter yarn or strand usually treated with a surface coating, lubricant or both, intended to be used to stitch one or more pieces of material or an object to a material. It may be defined as smooth, evenly spun, hard-twisted ply yarn, treated by a special finishing process to make it resistant to stresses in its passage through the eye of a needle and through material involved in seaming and stitching operations1.

Sewing threads are used in garments, upholstery, air-supported fabric structures and geotextiles to join different components by forming a seam. The primary function of a seam is to provide uniform stress transfer from one piece of fabric to another, thus preserving the overall integrity of the fabric assembly.

Seam can be formed by the following techniques:

- Mechanical: stapling, sewing.

- Physical: welding or heat-setting.

- Chemical: by means of resins2.

The formation of seams by physical and chemical methods is restricted to a few specialised applications, as these processes tend to alter certain properties of the textile material. Among mechanical sewing techniques, sewing maintains its prevailing position by virtue of its simplicity, sophisticated and economical production methods and the controllable elasticity of the seam produced.

Different types of sewing threads

Usually, sewing threads are manufactured from either natural or manmade fibres in either staple or filament form3. A broad classification of different types of sewing threads is given below:

Classification of Sewing Thread

Properties of Sewing Threads | Essential Properties Required for Sewing Threads

Essential properties required for sewing threads: Industrial sewing techniques make specific and often very exacting demands on the threads involved in the sewing process. The sewability of sewing threads is of major importance6, having a very profound effect on seam quality and production costs. The sewing and the seam performance of a sewing thread are largely influenced by the material to be sewn, the sewing technique and the end-use for which the sewn material is intended. These requirements can be defined as:

* The ability of the sewing thread to meet the functional requirements of producing the desired seam effectively.

* The ability of the sewing thread to provide the desired aesthetics and serviceability in the seam.

* The cost of sewing thread and that associated with producing the desired seam.

The different important properties required by a sewing thread are discussed below:

1. Needle thread must pass freely through the small eye of the needle; consequently they must be uniform, knot-free, non-torque and fault free.

2. Tensile strength/breaking strength is one of the essential properties of the thread. It must be capable of withstanding several kinetic/lateral movements during sewing. The strength of the sewing thread must be higher than that of the fabric so that the thread does not rupture during use. During sewing at high speeds, the needle thread is subjected to repeated tensile stresses at very high rates. The thread also comes under the influence of heat, bending, pressures, torsion and wearing. The value of these stresses depends on the sewing speed, machine settings and the thread used. The stresses created within the thread have a negative effect on the processing and functional characteristics of the thread, and there is significant reduction in the thread strength after sewing.

This is a function of the dynamic and thermal loading of the thread and is influenced by the thread frictional properties, thread tensioning during sewing, needle size, stitch length and number of fabric layers in the seam. The thread should therefore possess adequate strength and elongation in order to perform satisfactorily during sewing and in seam 7.

3. For good performance in a sewing machine moderate to low extension-at-break of the thread is usually preferred. Needle thread with different elongation-at-break has been found to behave quite differently during stitch formation. The determinants of success of sewing a thread with certain elongation per cent without any problem are the machine setting and special properties of the sewing thread itself 6.

4. The elasticity of the sewing thread must be uniform along its length in order to enable equal length stitches to be formed, and it must closely match the elasticity of the fabric being sewn; otherwise either seam thread fracture, or tearing of the adjacent fabric may arise during garment use. Clearly, the requirements of woven and knitted fabrics will be different.

5. The forces that are developed in the sewing thread are mostly due to the friction between the thread and machine parts, the most severe action taking place between:

- The thread and the needle.

- The thread and the fabric being sewn.

A controlled level of both static and dynamic friction is required; this must not be too high, which could cause lack of thread control. High static friction values are necessary to allow the stitches to lock and prevent “run-back” of seams. Spun threads are particularly good in this respect when compared with filament thread. The worst is the monofilament threads. The frictional properties are affected by lubrication. The factors that influence the frictional properties are:

• Uniform application of lubricating agents.
• Adhesion of the finishing agent on the thread.

The quantity and quality of finishes are very important. Special finishes like silicone compounds have been found to exhibit clear advantage over standard paraffin wax.

6. Good abrasion resistance is essential for good sewing performance. The thread is under tension condition, especially when the stitch is being set. The thread must be resilient enough to return to shape after the distortions, and then must maintain its physical properties to provide good performance in the seam after the sewing process is complete. Nylon and polyester offer the best resistance to abrasion.

7. Good resistance to heat is a very important requirement of a sewing thread. The temperature reached by the sewing needle during sewing very much depends on:

* the nature of the fabric to be sewn (density, thickness, finish)

* the speed of the sewing machine

* the type of needle used (size, shape, surface finish)

* size and finish of the sewing thread.

The needle temperature is especially critical for fabrics and sewing threads of thermoplastic fibres, where it may exceed their melting temperature. Needle heating causes sewing thread breakage, cross-thread, skipped stitches, seam damage and physical damage to the needle.

Various studies show that the sewing thread influences the needle temperature significantly. Its movement through the needle reduces the needle temperature by an average of 21- 45%, the amount of reduction depends on the sewing condition and the structure, fineness and composition of sewing thread.

Lubrication of sewing thread with a mixture of wax, emulsions with synthetic resins, and silicon based products may minimise heat generation, and the fibres surface of spun yarns may be an advantage in that a thin layer of the surrounding air will move with the thread and promote needle cooling.

8. The hairiness of sewing thread also affects the appearance of the seam. Sewing threads for decorative seams are singed, squeezed and gloss-brushed.

9. The final direction of twist insertion may be important to enable the stitch forming mechanism of the sewing machine to perform correctly; most sewing machine require Z twist, but there are a few where performance is better with S twist.

10. Colour fastness is a general requirement for sewing thread. It is important that the selected shade retain its colour throughout the life of the garment. Two aspects of fastness are important:

• The thread must not change colour.

• The thread must not stain any material adjacent to the seam.

11. Low shrinkage during washing and ironing is required. Shrinkage due to fibre swelling causes seams to pucker, especially if the fabric exhibits less shrinkage than threads. Synthetic threads suffer less from this problem than cotton threads owing to their much lower moisture absorbency; however they are liable to residual shrinkage problems if unsuitable manufacturing processes are employed. Synthetic threads can suffer from the problem of thermal shrinkage during ironing but this difficulty can be solved by the use of high temperature setting, which stabilises the thread at temperature above those normally encountered during the ironing process.

The sewing threads should possess better evenness and should contain minimal number of knots, faults and neps, etc. Thread should have very low level of imperfections and classimat faults.

12. Good lustre in the thread improves appearance of the seam. 

13. Threads must be uniformly dyed in a good match to the materials being sewn and also the dyed thread should have properties like colourfastness to washing, light, perspiration, and sublimation.

14. The ability of the thread to perform efficiently in the sewing machine is defined sewability. It can be assessed by the number of breaks that occur during the sewing of a certain number of stitches. However, owing to the generation of needle heat in high-speed sewing, the threads could be damaged without breaking. The long knot-free evenner yarns in case of rotor and air-jet can give better sewability.

15. The characteristics of properly constructed seam are strength, elasticity, durability, stability and appearance. The relative importance of these qualities is determined by the end-use of the sewn product. The factors that govern these properties are seam and stitch type, thread strength and elasticity, stitches per unit length of seam, thread tension, seam efficiency of the material. The hairiness of sewing thread is important to decide seam appearance. The shrinkage potential of the thread and hence the seam is also major importance for proper seam appearance. The serviceability of a garment depends not only on the quality of the fabric but also on that of the seam. The seam quality is measured by stitching parameters of the threads and seam parameters such as size, slippage and strength. 

The failure of seam produced by traverse loading can generally be classified as: Type I: the failure due to thread breakage, Type II: the failure due to fabric breakage, Seam breakage: the failure due to the slippage of cloth yarns at right angle to the seam. 

Seam slippage is the most probable cause for seam failure that leads to garment rejection in wear. The durability of a seam depends largely on its strength and its relationship with elasticity of the material. It is measured in terms of seam efficiency, where Seam Efficiency = (Seam tensile strength/fabric tensile strength) x 100, generally ranges between 85 to 90%. The minimum loop strength correlates well with the stitch breaking strength. Further resistance to abrasion and wear of the seam during everyday use, including laundering is also essential for the longer seam.

16. Seam pucker can be defined as a differential shrinkage occurring along the line of a seam and is mainly caused due to seam instability, due to high tension imposed during sewing. Though currently available threads have a certain amount of controlled elasticity and elongation they get over-stretched when the sewing tensions are high. During relaxation the thread recovers its original length, thus gathering up the seam. Threads for use in apparel are also required to have good stability to laundering, ironing and other treatments since differential shrinkage between the sewing thread and the fabric of a garment can cause puckering.

Further, Seam pucker can be determined by measuring the differences in fabric and seam thickness under a constant compressive load. The seam-thickness strain is calculated by using the formula:

Thickness strain (%) = (seam thickness – 2 x fabric thickness) x 100 / 2x fabric thickness {ref}

Modern Blow Room Line | The Installation as a Sequence of Blowroom Machines | Modern Blow Room Line for American

In processing the material, different types of machines are necessary, namely those suitable for  opening, those for cleaning and those for blending. Different intensities of processing are also required, because the tufts continually become smaller as they pass from stage to stage.Accordingly, while a coarsely clothed cleaning assembly is ideal after the bale opener, for example, it is inappropriate at the end of the line.

 Therefore, there are no universal machines, and a blowroom line is a sequence of different machines arranged in series and connected by transport ducts. In its own position in the line, each machine gives optimum performance – at any other position it gives less than its optimum. Also there may be advantages in different modes of transport, feeding, processing, cleaning and so on from one machine to another along the line. Finally, the assembly of a blowroom line depends among other things on:

Modern Blow Room Line

• the type of raw material;
• the characteristics of the raw material;
• waste content;
• dirt content;
• material throughput;
• the number of different origins of the material in a given blend. 

In most cases a modern blowroom line consists of the following machines, as shown in Fig. 8 (Rieter) and Fig. 9 (Trützschler), illustrating two typical blowroom lines.

Modern blow room line for American:

Pima Cotton:

Blendomat

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Heavy material separator

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Multiple mixture

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CVT1 (fine) / CVT3 (coarse)

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Dustex

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Feeding unit (chute feed) for card

? Modern blow room for American upland cotton containing more than 3% trash:

Blendomat

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Heavy material separator

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Multiple mixture

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Dustex

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Feeding unit for card

Draw frame | Actions involved in Draw Frame | Tasks of Draw frame | Working Process of Draw Frame

Draw frame is a machine for combining and drawing slivers of a textile fiber (as of hemp for rope manufacture or cotton for spinning) . Drawing is the operation by which slivers are blended, doubled and leveled. In short staple spinning the term is only applied to the process at a draw frame.

In drawing slivers are elongated when passing through a group of pair rollers, each pair is moving faster than previous one.

Actions involved in Draw Frame

Drafting: It is the process of increasing length per unit weight of sliver. It is mainly due to peripheral speed of the rollers.

Doubling: The process of combing two or more carded sliver into a single form is called doubling. In draw frame m/c generally six slivers are fed to convert into one i.e. six doubling.

Drawing: In the cotton industry the term is applied exclusively to processing on the draw frame, where the operation is one of doubling and drafting. Drawing= Drafting + Doubling.

Tasks of Draw frame

• Equalizing

• Parallelizing

• Blending

• Dust removal

Equalizing: One of the main tasks of draw frame is improving evenness over short, medium and especially long terms. Carded slivers are fed to the draw frame have degree on unevenness that cannot be tolerated in practice and slivers from the comber contain the “infamous” piecing. It is obscured by draw frame.

Equalizing is always performed by a first process, namely doubling and can optionally also be performed by a second process, namely auto leveling. The draft and the doubling have the same value and lie in the range of 6 to 8.

Parallelizing: To obtain an optional value for strength in the yarn characteristics, the fibers must be arranged parallel in the fiber strand. The draw frame has the tasks of creating this parallel arrangement. It fulfills the task by way of the draft, since every drafting step leads to straightening the fibers.

Blending: In addition to the equalizing effect, doubling also provides a degree of compensation of raw material variation by blending. Their results are exploited in particular way in the production of blended yarns comprising cotton or synthetic blends. At the draw frame metering of the individual components can be carried out very simply be selection of the number of slivers entering the machines.

Dust Removal: Dust is steadily becoming a greater problem both in processing and for the personnel involved. It is therefore important to remove dust to the greatest practical extent at every possible point within the overall process.

Dust removal can only be carried out to a significant when there are high levels of fiber. Since a large function the smallest particles adhere relatively strong to the fibers. High performance draw frame is equipped with appropriate suction removal systems; more than 80% of the incoming dust is extracted.

Drawing or Draw Frame | Objects of drawing | Importance or Necessity of Draw frame

Drawing is the operation by which slivers are blended, doubled and leveled. In short staple spinning the term is only applied to the process at a draw frame. In drawing slivers are elongated when passing through a group of pair rollers, each pair is moving faster than previous one. This permits combing, drawing and elongating of several slivers to make them strong and uniform.In most modern worsted drawing sets there are 3 passages of pin drafting and roving process.

Objects of drawing

1. To straighten the crimped, curled and hooked fibers.
2. To make the fiber parallel to their neighbors.
3. To improve uniformity of fibers by drafting and doubling.
4. To reduce weight per length unit of sliver.
5. To remove dust from slivers.
6. To blend raw material of same hank perfectly.

Importance or Necessity of Draw frame

To parallelization of fiber and blending the carded sliver, draw frame is needed.

In carded sliver, fibers are present in hook form i.e. trailing hooks and leading hooks. To parallel these hooks raw frame is used.

Majority of the fiber hooks in a carded sliver are trailing hooks while leading hooks are comparatively less. Trailing hooks are also known as major hooks, while leading hooks are known as minor hooks.

Process Flow Chart of Carded Yarn Manufacturing Process

If you want to make a yarn you will have two method to follow. One is Carded yarn manufacturing method and another is Combed yarn manufacturing method.

Combed yarn is most precious, finer and thiner than the carded yarn. Because the Carded Yarn is produced by following some less manufacturing steps than the Combed Yarn.

So let us know about the carded yarn manufacturing.

 Flow Chart of Carded Yarn Manufacturing:

Input Material ———Processing Machines ——–Output Materials

Raw Cotton »»> Blow Room»»»Lap

Lap»»»»»>Carding»»»»>Carded Sliver

Carded Sliver»»Drawing 1»»»»Drawn Sliver

Breaker Sliver»>Drawing 2»»»»Finisher Drawn Sliver

Finisher Drawn Sliver»Simplex/ Speed Frame»»Roving

Roving»»»»Ring Frame»»»>Yarn

Yarn»»»»>Winding»»»»>Yarn In Large Package.

The process flowchart of Yarn Manufacturing mentioning above is currently followed by the Textile Spinning Mills.

Dyeing Process | Process of Dyeing | The Chemistry of the Dyeing Process

The dyeing of a textile fiber is carried out in a solution, generally aqueous, known as the dye liquor or dye bath. For true dyeing to have taken place, coloration of fabric and absorption are important determinants. 

Coloration: 

The coloration must be relatively permanent: that is not readily removed by rinsing in water or by normal washing procedures. Moreover, the dyeing must not fade rapidly on exposure to light. 

Absorption: 

The process of attachment of the dye molecule to the fiber is one of absorption: that is the dye molecules concentrate on the fiber surface. There are four kinds of forces by which dye molecules are bound to the fiber: 

1) Ionic forces 2) Hydrogen bonding 3) Vander Wals’ forces and 4) Covalent chemical linkages

Dyeing of Wool: 

In the dyeing of wool which is a complex protein containing about 20 different amino acids, the sulfuric acid added to the dye bath forms ionic linkages with the amino groups of the protein. In the process of dyeing, the sulfate anion (negative ion) is replaced by a dye anion. In the dyeing of wool, silk and synthetic fibers, hydrogen bonds are probably set up between the azo, amino, alkyl amino and other groups and the amino Co-NH-groups. Covalent chemical links are brought about in the dye-bath by chemical reaction between a fiber-reactive dye molecule, one containing a chemically reactive center and a hydro-oxy group of a cotton fiber, in the presence of alkali. 

The Chemistry of the Dyeing Process : 

Exhaustion In any dyeing process, whatever the chemical class of dye being used, heat must be supplied to the dye bath; energy is used in transferring dye molecules from the solution to the fiber as well as in swelling the fiber to render it more receptive. The technical term for this process is exhaustion. Levelness: An Important Quality 

Evenness of dyeing, known as levelness is an important quality in the dyeing of all forms of natural and synthetic fibers. It may be attained by the control of dyeing conditions viz. 

• By agitation to ensure proper contact between dye liquor and substance being dyed and by use of restraining agents to control rate of dyeing or strike. Solvent Dyeing Serious consideration has recently been given to the methods of dyeing in which water as the medium is replaced by solvents such as the chlorinated hydrocarbons used in dry cleaning. The technological advantages in solvent dyeing are: 1. Rapid wetting of textiles 
• Less swelling 
• Increased speed of dyeing per given amount of material 
• Savings in energy, as less heat is required to heat or evaporate per-chloro-ethylene. Thus it eliminates the effluent (pollution) problems associated with the conventional methods of dyeing and finishing.

Dyeing Methods | Methods of Dyeing | Chain Dyeing | Cross Dyeing | Stock dyeing | Top dyeing | Yarn dyeing | Bale Dyeing | Batik Dyeing | Skein (Hank) Dyeing | Package Dyeing | Warp-beam Dyeing | Space Dyeing | Piece Dyeing | Beck dyeing | Jig dyeing | Pad dyeing | Jet dyeing | Solution pigmenting or dope dyeing | Garment dyeing | Random Dyeing

Dyeing Methods

Color is applied to fabric by different methods and at different stages of the textile manufacturing process. The process of applying color to fiber stock, yarn or fabric is called dyeing.” There may or may not be thorough penetration of the colorant into the fibers or yarns.

Dyes can be used on vegetable, animal or man made fibers only if they have affinity to them. Textile dyes include acid dyes, used mainly for dyeing wool, silk and nylon and direct or substantive dyes, which have a strong affinity for cellulose fibers. Mordant dyes require the addition of chemical substances, such as salts to give them an affinity for the material being dyed. They are applied to cellulose fibers, wool or silk after such materials have been treated with metal salts. Sulfur dyes, used to dye cellulose, are inexpensive, but produce colors lacking brilliance. Azoic dyes are insoluble pigments formed within the fiber by padding, first with a soluble coupling compound and then with a diazotized base. Vat dyes, insoluble in water, are converted into soluble colorless compounds by means of alkaline sodium hydrosulfite. These colorless compounds are absorbed by the cellulose, which are subsequently oxidized to an insoluble pigment. Such dyes are colorfast. Disperse dyes are suspensions of finely divided insoluble, organic pigments used to dye such hydrophobic fibers as polyesters, nylon and cellulose acetates.

Garment dyeing

Reactive dyes combine directly with the fiber, resulting in excellent colorfastness. The first ranges of reactive dyes for cellulose fibers were introduced in the mid-1950. Today, a wide variety is available.

Dyeing Methods | Methods of Dyeing

1. Chain Dyeing
2. Cross Dyeing
3. Stock dyeing
4. Top dyeing
5. Yarn dyeing
6. Bale Dyeing
7. Batik Dyeing
8. Skein (Hank) Dyeing
9. Package Dyeing
10. Warp-beam Dyeing
11. Space Dyeing
12. Piece Dyeing
13. Beck dyeing
14. Jig dyeing
15. Pad dyeing
16. Jet dyeing
17. Solution pigmenting or dope dyeing
18. Garment dyeing
19. Random Dyeing

Chain Dyeing
This is used when yarns and cloth are low in tensile strength. Several cuts or pieces of cloth are tacked end-to-end and run through in a continuous chain in the dye color. This method affords high production.

Cross Dyeing
This is a very popular method in which varied color effects are obtained in the one dye bath for a cloth which contains fibers with varying affinities for the dye used. For example, a blue dyestuff might give nylon 6 a dark blue shade, nylon 6, 6 a light blue shade, and have no affinity for polyester area unscathed or white.

Stock Dyeing
Stock dyeing is used to dye fibers. In this process, the staple fibers are packed into a vessel and then dye liquid is forced through them. Although the dye solution is pumped in large quantities, the dye may not penetrate completely into the fibers and some areas may be left without dyeing. However, the following blending and spinning processes mix up the fibers in such a thorough way that it results in an overall even color. Woolens are usually stock dyed.

Top dyeing
Top is the combed wool sliver. It is wound on perforated spools and the dye solution is circulated through it. This method results in very even dyeing.

Yarn Dyeing
Stock dyeing is used to dye fibers. In this process, the staple fibers are packed into a vessel and then dye liquid is forced through them. Although the dye solution is pumped in large quantities, the dye may not penetrate completely into the fibers and some areas may be left without dyeing. However, the following blending and spinning processes mix up the fibers in such a thorough way that it results in an overall even color. Woolens are usually stock dyed.

When dyeing is done after the fiber has been spun into yarn, it is called yarn dyeing. In this method, the dyestuff penetrates the fibers to the core of the yarn. There are many forms of yarn dyeing- Skein (Hank) Dyeing, Package Dyeing, Warp-beam Dyeing,and Space Dyeing.

Bale Dyeing
This is a low cost method to dye cotton cloth. The material is sent without scouring or singeing, through a cold water bath where the sized warp has affinity for the dye. Imitation chambray and comparable fabrics are often dyed this way.

Batik Dyeing
This is one of the oldest forms known to man. It originated in Java. Portions of the fabric are coated with wax so that only un-waxed areas will take on the dye matter. The operation may be repeated several times and several colors may used for the bizarre effects. Motifs show a mlange, mottled or streaked effect, imitated in machine printing.

Skein (Hank) Dyeing
The yarns are loosely arranged in skeins or coils. These are then hung over a rung and immersed in a dyebath in a large container. In this method, the colour penetration is the best and the yarns retain a softer, loftier feel. It is mostly used for bulky acrylic and wool yarns.

Package Dyeing
The yarns are wound on spools, cones or similar units and these packages of yarn are stacked on perforated rods in a rack and then immersed in a tank. In the tank, the dye is forced outward from the rods under pressure through the spools and then back to the packages towards the center to penetrate the entire yarn as thoroughly as possible. Mostly, the carded and combed cotton which are used for knitted outerwear is dyed through this method.

Warp-beam Dyeing
It is similar to package dyeing but more economical. Here, the yarn is wound on to a perforated warp beam and then immersed in a tank for dyeing it applying pressure.

Space Dyeing
In this method, the yarn is dyed at intervals along its length. For these two procedures- knit- deknit method and OPI Space-Dye Applicator- are adopted. In the first method, the yarn is knitted on either a circular or flat-bed knitting machine and the knitted cloth is then dyed and subsequently it is deknitted. Since the dye does not readily penetrate the areas of the yarn where it crosses itself, alternated dyed and undyed spaces appear. The OPI Space-Dye Applicator technique produces multi coloured space- dyed yarns. The yarns are dyed intermittently as they run at very high speeds through spaced dyebaths. They are continuously subjected to shock waves produced by compressed air having supersonic velocities.

Piece Dyeing
The constructed fabrics are piece dyed for the flexibility they provide. The textile manufacturer can dye the whole fabric in batches according to the fashion demands of the time thus avoiding wastage and resultantly loss. There are several methods prevalent or piece dyeing.

Beck dyeing
It is used for dyeing long yards of fabric. The fabric is passed in rope form through the dyebath. This rope of the fabric moves over a rail onto a reel which immerses it into the dye and then draws the fabric up and forward and brings it to the front of the machine. This process is repeated many times until the desired color intensity is obtained.

Jig dyeing
It is similar to the process of beck dyeing with a slight variation. The fabric in jig dyeing is held on rollers at full width rather than in rope form as it is passed through the dyebath.

Pad dyeing
Padding is also done while holding the fabric at full width. The fabric is passed through a trough having dye in it. Then it is passed between two heavy rollers which force the dye into the cloth and squeeze out the excess dye. Then it is passed through a heat chamber for letting the dye to set. After that it is passed through washer, rinser and dryer for completing the process.

Jet dyeing
Fabric is placed in a heated tube where jets of dye solution are forced through it at high pressures. The fabric too moves along the tube. The solution moves faster than the cloth while coloring it thoroughly.

Solution pigmenting or dope dyeing
This is a method applied for dyeing the synthetic fibers. Dye is added to the solution before it is extruded through the spinnerets for making synthetic filaments. This gives a colorfast fiber as the pigments are used which are the fastest known colors.

Garment dyeing
When the finished textile product such as hosiery or sweaters are dyed, it is called garment dyeing. A number of garments are packed loosely in a nylon net and put into a dyestuff filled tub with a motor driven paddle. The dye is thrown upon the garments by the moving paddles’ effect.

Random Dyeing
Coloring only certain designated portions of the yarn. There are three ways of doing this type of coloring:

Skeins may be tightly dyed in two or more places and dyed at one side of the dye with one color and at the other side with another one. Color may be printed onto the skeins which are spread out on the blanket fabric of the printing machine.

Cones or packages of yarn on hollow spindles may be arranged to form channels through which the yarn, by means of air-operated punch, and the dyestuff are drawn through these holes by suction. The yarn in the immediate area of the punch absorbs the dye and the random effects are thereby attained.

Dyeing Process | Different Types of Dye | Classification of Dyes | Various Classes and Types | Acid Dyes | Natural Dyes | Basic (Cationic) Dyes | Synthetic Dyes | Direct (substantive) Dyes | Disperse Dyes | Sulfur Dyes | Pigment Dyes | Mordant Dyes | Vat Dye | Reactive Dyes | Macromolecular Dyes | Metallized Dyes | Naphthol Dyes | Premetallized Dyes | Gel Dyeing | Developed Dyes | Azo Dyes | Aniline Dyes | Anthraquinone Dyes

A process of coloring fibers, yarns, or fabrics with either natural or synthetic dyes. Dyeing is an ancient art which predates written records. It was practised during the Bronze age in Europe. Primitive dyeing techniques included sticking plants to fabric or rubbing crushed pigments into cloth
. The methods became more sophisticated with time and techniques using natural dyes from crushed fruits, berries and other plants, which were boiled into the fabric and gave light and water fastness (resistance), were developed. Dyeing can be done at any stage of the manufacturing of textile- fiber, yarn, fabric or a finished textile product including garments and apparels. The property of color fastness depends upon two factors- selection of proper dye according to the textile material to be dyed and selection of the method for dyeing the fiber, yarn or fabric

Dyes

Substances that add color to textiles. They are incorporated into the fiber by chemical reaction, absorption, or dispersion. Dyes differ in their resistance to sunlight, perspiration, washing, gas, alkalies, and other agents; their affinity for different fibers; their reaction to cleaning agents and methods; and their solubility and method of application. 

Various classes and types are listed below:

• Acid Dyes
• Natural Dyes 
• Basic (Cationic) Dyes
• Synthetic Dyes
• Direct (substantive) Dyes 
• Disperse Dyes
• Sulfur Dyes
• Pigment Dyes
• Mordant Dyes
• Vat Dyes
• Reactive Dyes
• Macromolecular Dyes
• Metallized Dyes
• Naphthol Dyes
• Premetallized Dyes
• Gel Dyeing
• Developed Dyes
• Azo Dyes
• Aniline Dyes
• Anthraquinone Dyes

Acid Dyes

A class of dyes used on wool, other animal fibers, and some manufactured fibers. Acid dyes are seldom used on cotton or linen since this process requires a mordant. Acid dyes are widely used on nylon when high washfastness is required. In some cases, even higher washfastness can be obtained by aftertreatment with fixatives.

Natural Dyes 

Direct Printing, it is the most common approach to apply a color pattern onto a fabric. If done on colored fabric, it is known as overprinting. The desired pattern is produced by pressing dye on the fabric in a paste form. To prepare the print paste, a thickening agent is added to a limited amount of water and dye is dissolved in it. Earlier starch was preferred as a thickening agent for printing. Nowadays gums or alginates derived from seaweed are preferred as they allow better penetration of color and are easier to wash out. Most pigment printing is done without thickeners because the mixing up of resins, solvents and water produces thickening anyway.

Basic (Cationic) Dyes

 Basic dyes are water-soluble and are mainly used to dye acrylic fibers. They are mostly used with a mordant. A mordant is a chemical agent which is used to set dyes on fabrics by forming an insoluble compound with the dye. With mordant, basic dyes are used for cotton, linen, acetate, nylon, polyesters, acrylics and modacrylics. Other than acrylic, basic dyes are not very suitable for any other fiber as they are not fast to light, washing or perspiration. Thus, they are generally used for giving an after treatment to the fabrics that have already been dyed with acid dyes.

Synthetic Dyes

Synthetic dyes are classified based upon their chemical composition and the method of their application in the dyeing process.

Direct (substantive) Dyes 

Dyes Direct dyes color cellulose fibers directly without the use of mordants. They are used for dyeing wool, silk, nylon, cotton, rayon etc. These dyes are not very bright and have poor fastness to washing although they are fairly fast to light.

Disperse Dyes

Disperse Dyes Disperse dyes are water insoluble. These dyes are finely ground and are available as a paste or a powder that gets dispersed in water. These particles dissolve in the fibers and impart color to them. These dyes were originally developed for the dyeing of cellulose acetate but now they are used to dye nylon, cellulose triacetate, and acrylic fibers too.

Sulfur Dyes

Sulfur Dyes Sulfur Dyes are insoluble and made soluble by the help of caustic soda and sodium sulfide. Dyeing is done at high temperature with large quantities of salt so that the color penetrates into the fiber. After dyeing the fabric is oxidized for getting desired shades by exposure to air or by using chemicals. Excess dyes and chemicals are removed by thorough washing. These dyes are fast to light, washing and perspiration and are mostly used for cotton and linen.

Pigment Dyes

Pigment Dyes Although pigments are not dyes in a true sense, they are extensively used for coloring fabrics like cotton,wool and other manmade fibers due to their excellent light fastness. They do not have any affinity to the fibers and are affixed to the fabric with the help of resins. After dyeing, the fabrics are subjected to high temperatures.

Mordant Dyes

Mordant Dyes The mordant or chrome dyes are acidic in character. Sodium or potassium bichromate is used with them in the dyebath or after the process of dyeing is completed. This is done for getting the binding action of the chrome. They are mostly used for wool which gets a good color fastness after treatment with mordant dyes. They are also used for cotton, linen, silk, rayon and nylon but are less effective for them.

Vat Dyes

Vat Dyes Vat dyes are insoluble in water and cannot dye fibers directly. However, They can be made soluble by reduction in alkaline solution which allows them to affix to the textile fibers. Subsequent oxidation or exposure to air restore the dye to its insoluble form. Indigo is the original vat dye. These dyes are the fastest dyes for cotton, linen and rayon. They are used with mordants to dye other fabrics such as wool, nylon, polyesters, acrylics and modacrylics.

Reactive Dyes

Reactive Dyes Reactive dyes react with fiber molecules to form a chemical compound. These dyes, they are either applied from alkaline solution or from neutral solutions which are then alkalized in a separate process. Sometimes heat treatment is also used for developing different shades. After dyeing, the fabric is washed well with soap so as to remove any unfixed dye. Reactive dyes were originally used for cellulose fibers only but now their various types are used for wool, silk, nylon, acrylics and their blends as well.

Macromolecular Dyes

 A group of inherently colored polymers. They are useful both as polymers and as dyes with high color yield. The chromophores fit the recognized CI classes, i.e., azo, anthraquinone, etc., although not all CI classes are represented. Used for mass dyeing, hair dyes, writing inks, etc.

Metallized Dyes

 A class of dyes that have metals in their molecular structure. They are applied from an acid bath.

Naphthol Dyes

A type of azo compound formed on the fiber by first treating the fiber with a phenolic compound. The fiber is then immersed in a second solution containing a diazonuim salt that reacts with the phenilic compound to produce a colored azo compound. Since the phenolic compound is dissolved in caustic solution, these dyes are mainly used for cellulose fiber, although other fibers can be dyed by modifying the process. (Also see DYES, Developed Dyes.)

Premetallized Dyes

Acid dyes that are treated with coordinating metals such as chromium. This type of dye has much better wetfastness than regular acid dye. Premetallized dyes are used on nylon, silk, and wool.

Gel Dyeing

Passing a wet-spun fiber that is in the gel state (not yet at full crystallinity or orientation) through a dyebath containing dye with affinity for the fiber. This process provides good accessibility of the dye sites.

Developed Dyes

Dyes that are formed by the use of a developer. The substrate is first dyed in a neutral solution with a dye base, usually colorless. The dye is then diazotized with sodium nitrate and an acid and afterwards treated with a solution of B-naphthol, or a similar substance, which is the developer. Direct dyes are developed to produce a different shade or to improve washfastness or lightfastness.

Azo Dyes

Dyes characterized by the presence of an azo group (-N=N-) as the chromophore. Azo dyes are found in many of the synthetic dye classes.

Aniline Dyes

Dyes derived chemically from aniline or other coal tar derivatives.

Anthraquinone Dyes

Dyes that have anthraquinone as their base and the carbonyl group (>C=O) as the chromophore. Anthraquinone-based dyes are found in most of the synthetic dye classes.

Printing Method | Method of Printing | Printing Processes | Different Types of Printing Method | Block Printing | Roller Printing | Screen Printing | Transfer Printing | Heat Transfer Printing | Ink-Jet Printing | Carpet Printing | Warp Printing | Resist Printing | Photographic Printing | Pigment Printing | Blotch Printing | Burn-Out Printing | Direct Printing | Discharge Printing | Duplex Printing

Printing Processes:There are five main methods of printing a fabric, these being the block, roller, screen, heat transfer and ink-jet methods. The heat transfer method differs from the others in that it involves the transfer of color from the design printed on paper through the vapour phase into the fibres of the fabric. With the other methods the dye or pigment is applied to the fabric surface through a print paste medium. The ink jet printing process however is a comparatively recent innovation and is referred to as a ‘non-impact’ method, because the print paste is fired on to the textile from a jet which is not actually in contact with the fabric.

DIFFERENT TYPES OF PRINTING METHOD

Block Printing :

The blocks are usually made of wood and the design is hand carved, so that it stands out in relief against the background surface. The print paste is applied to the design surface on the block and the block then pressed against the fabric. The process is repeated with different designs and colours until the pattern is complete. 

Block printing is a slow, laborious process and is not suitable for high volume commercial use. It is a method still practised in the oriental countries where markets exist for the types of printed fabrics produced.

Roller Printing:

Roller printing has traditionally been preferred for long production runs because of the very high speeds possible. It is also a versatile technique since up to a dozen different colours can be printed simultaneously. The basic roller printing equipment, shown in Fig. 7.1, consists of a number of copper faced rollers in which the design is etched. There is a separate printing roller for each colour being printed. Each of the rollers rotates over the fabric under pressure against an iron pressure roller. A blanket and backing cloth rotate over the pressure roller under the fabric and provide a flexible support for the fabric being printed. A colour doctor blade removes paste or fibres adhering to the roller after contact with the fabric. After the impression stage the fabric passes to the drying and steaming stages.

Screen Printing :

This type of printing has increased enormously in its use in recent years because of its versatility and the development of rotary screen printing machines which are capable of very high rates of production. An additional significant advantage is that heavy depths of shade can be produced by screen printing, a feature which has always been a limitation of roller printing because of the restriction to the amount of print paste which can be held in the shallow depth of the engraving on the print roller. Worldwide, some 61% of all printed textile fabric is produced by the rotary screen method and 23% by flat screen printing. 

There are two basic types of screen printing process, the flat screen and the rotary screen methods. 

Heat Transfer Printing :

Transfer printing techniques involve the transfer of a design from one medium to another. The most common form used is heat transfer printing in which the design is printed initially on to a special paper, using conventional printing machinery. The paper is then placed in close contact with the fabric and heated, when the dyes sublime and transfer to the fabric through the vapor phase.

Ink-Jet Printing :

There has been considerable interest in the technology surrounding non-impact printing, mainly for the graphic market, but the potential benefits of reductions in the time scale from original design to final production has led to much activity in developing this technology for textile and carpet printing processes. The types of machines developed fall into two classes, drop-on-demand (DOD) and continuous stream (CS).

Carpet Printing :

The printing of carpets only really achieved importance after the introduction of tufted carpets in the late 1950s. Until then the market was dominated by the woven Wilton carpets and Axminster designs were well established, but by the 1980s tufted carpet production accounted for some 80% (by area) of UK production. Much of this carpet production was printed because the range of patterns possible to produce using tufting machines was limited and there was a desire to produce a greater flexibility of design for these types of carpet

Warp Printing: 

The printing of a design on the sheet of warp yarns before weaving. The fillingis either white or a neutral color, and a grayed effect is produced in the areas of the design.

Resist Printing:

A printing method in which the design can be produced: (1) by applying a resistagent in the desired 

design, then dyeing the fabric, in which case, the design remains whitealthough the rest of the fabric is dyed; or (2) by including a resist agent and a dye in the pastewhich is applied for the design, in which case, the color of the design is not affected bysubsequent dyeing of the fabric background.

Photographic Printing:

A method of printing from photoengraved rollers. The resultant designlooks like a photograph. The designs may also be photographed on a silk screen which is used inscreen printing.

Pigment Printing:

Printing by the use of pigments instead of dyes. The pigments do notpenetrate the fiber but are affixed to the surface of the fabric by means of synthetic resins whichare cured after application to make them insoluble. The pigments are insoluble, and application isin the form of water-in-oil or oil-in-water emulsions of pigment pastes and resins. The colorsproduced are bright and generally fat except to crocking.

Blotch Printing: 

A process wherein the background color of a design is printed rather than dyed.

Burn-Out Printing: 

A method of printing to obtain a raised design on a sheer ground. Thedesign is applied with a special chemical onto a fabric woven of pairs of threads of differentfibers. One of the fibers is then destroyed locally by chemical action. Burn-out printing is oftenused on velvet. The product of this operation is known as a burnt-out print.

Direct Printing: 

A process wherein the colors for the desired designs are applied directly to thewhite or dyed cloth, as distinguished from discharge printing and resist printing.

Discharge Printing: 

In “white” discharge printing, the fabric is piece dyed, then printed with apaste containing a chemical that reduces the dye and hence removes the color where the whitedesigns are desired. In “colored” discharge printing, a color is added to the discharge paste inorder to replace the discharged color with another shade.

Duplex Printing: 

A method of printing a pattern on the face and the back of a fabric with equalclarity. 

Printing Style | Style of Printing | Different Types of Printing Style | Direct Printing Style | Discharge Printing Style | Resist Printing Style

A process for producing a pattern on yarns, warp, fabric, or carpet by any of a largenumber of printing methods. The color or other treating material, usually in the form of a paste, is deposited onto the fabric which is then usually treated with steam, heat, or chemicals for fixation. 

There are three different printing 'styles' used to produce patterned effects on textiles, these being termed direct, discharge and resist. Each of these will be described in turn.

Direct Printing Style

This method involves the direct application of the colour design to the fabric and is the most common method of textile printing. The dyes used for direct printing are those which would normally be used for a conventional dyeing of the fabric type concerned.

Discharge Printing Style

In this method the fabric is pre-dyed to a solid shade by a traditional dyeing process and the colour is then destroyed locally, by chemicals incorporated in the print paste especially for that purpose. The result is a white patterned discharge on a coloured ground. In “white” discharge printing, the fabric is piece dyed, then printed with a paste containing a chemical that reduces the dye and hence removes the color where the white designs are desired. In “colored” discharge printing, a color is added to the discharge paste in order to replace the discharged color with another shade.

Resist Printing Style

In this method of printing the fabric is first printed with a substance called a ‘resist’ which will prevent the dye from being taken up in a subsequent dyeing process. The resist functions by either mechanically preventing the

dye from reaching local areas of the fabric or by chemically reacting with the dye or the fibre, to prevent adsorption. 

A printing method in which the design can be produced: (1) by applying a resistagent in the desired design, then dyeing the fabric, in which case, the design remains whitealthough the rest of the fabric is dyed; or (2) by including a resist agent and a dye in the pastewhich is applied for the design, in which case, the color of the design is not affected bysubsequent dyeing of the fabric background

Color Fastness Test | Washing Fastness Test | Washing Fastness | Color Fastness to Washing

The property of a dye to retain its color when the dyed (or printed) textile material is exposed to conditions or agents such as light, perspiration, atmospheric gases, or washing that can remove or destroy the color. A dye may be reasonably fast to one agent and only moderately fast to another. Degree of fastness of color is tested by standard procedures. Textile materials often must meet certain fastness specifications for a particular use.

It is always useful and interesting to test the dye which is to be used on a sample of the yarn or fabric to be dyed. The outcome will depend on the fabric, the mordant that has been used and dye that has have been chosen. Testing is best carried out on a series of Groundnuts marked (for identification) samples, which have been mordanted with a number of different mordants. Tests can be carried out for light, water and washing fastness using simple standard test methods.

To Test for Washing Fastness Follow these Steps :

• Take two pieces of fabric about 5cm by 5cm, one of which is undyed cotton and the other undyed wool. Stitch them together along one side.
• Take some sample strips of the dyed yarn and spread them evenly between the two pieces of cloth so that they overlap both sides. If dyed fibre is being tested a combed sample can be used in place of the yarn.
• Sew around all four sides of the cloth so that the yarn is held in place.
• Prepare a similar specimen with dyed materials that has satisfactory properties and place them in two jars with screw lids containing a solution of 5gm per litre soap or detergent solution at 30oC.
• Agitate the two jars gently for 30mins, then remove the fabrics and wash them gently in clean water for 5mins. Open the stitching and separate the pieces to dry in air. Examination:
• Place the dyed yarn next to a sample of the same material which has not been tested, and compare the change which has taken place. Compare also with the control sample with satisfactory properties. If the dyeing being tested shows equal or less change than the satisfactory sample, then it is as good as the satisfactory sample.
• Place the wool and cotton cloths next to samples of the same material which have not been tested and compare them with the cloths that have been tested with a satisfactory dyeing. Equal or less staining shows equal or better fastness.