Sunday, 14 October 2007

Back ground to the clothing industry: Why Garment Manufacturing Is Labour Intensive



Background to the Clothing Industry

The clothing industry is one of the most interesting industries because it combines fashion, fabric, labour, machines, speed, skill and market demand. A garment factory may employ only a few people, or it may employ thousands. This wide variation is mainly because of the special nature of fashion and clothing manufacture.

Unlike many other industries, garment manufacturing is not only a machine-based activity. It is strongly dependent on human handling, judgement and coordination. The fabric has to be spread, cut, bundled, stitched, finished, checked, packed and delivered according to market requirements.

Simple understanding:

The clothing industry is shaped by two major realities: fashion changes quickly, and sewing still needs a large amount of human skill.

1. Fashion Requires Quick Response

The first important feature of the clothing industry is the need for quick response. Fashion changes fast. Colours, styles, silhouettes, prints, trims and garment details may change from season to season, and sometimes even faster.

Because of this, clothing companies must be able to produce and deliver garments quickly. A delay in production may mean that the style becomes less attractive in the market.

Two Broad Types of Clothing

Clothing may be broadly divided into two categories:

Type of Clothing Meaning Production Nature
Fashion or couture garments Garments strongly influenced by style, design and current fashion trends. Usually produced in smaller quantities and often at higher cost.
Staple garments Regular garments such as underwear, shirts, school uniforms and basic clothing. Produced in larger quantities because demand is more stable.

The level of technology used in garment manufacture is closely related to the quantity produced and the length of the production run. If a style is produced in very large quantities for a long period, more mechanisation can be justified. But if a style is produced only in small quantities, too much investment in special machines may not be economical.

Practical point:
A basic school shirt may run in thousands of pieces, so production can be standardised. A fashion blouse or designer kurta may run in small quantities, so flexibility becomes more important than heavy mechanisation.

2. The Fashion Industry Is Labour Intensive

The clothing industry is also labour intensive. Entry into garment manufacturing is relatively easy compared with many other industries because the central operation is sewing. A small factory can begin with sewing machines, cutting tables, pressing equipment and trained operators.

However, this simplicity is also the reason why garment production depends heavily on people. Sewing may appear to be a simple operation, but it needs continuous fabric handling, alignment, judgement and control.

Why Sewing Dominates Garment Production

Sewing is the central process in garment manufacture. A garment is formed by joining different fabric components such as fronts, backs, sleeves, collars, cuffs, waistbands, pockets and linings.

In many sewing operations, the actual needle stitching time is only a part of the total operation time. A large part of the time is spent in handling activities such as:

  • Picking up the fabric parts
  • Matching and aligning edges
  • Folding or creasing fabric
  • Positioning under the presser foot
  • Trimming threads
  • Marking or checking seam positions
  • Disposing the sewn piece after stitching
  • Bundling parts for the next operation

This is why the productivity of a sewing line depends not only on machine speed, but also on operator skill, workplace layout, bundle movement, handling method and production planning.

Important learning:
In sewing, the machine may be fast, but the fabric must still be controlled by the operator. Therefore, garment manufacturing remains highly labour dependent.

Why Is Garment Manufacturing Difficult to Automate?

Garment manufacturing is difficult to automate mainly because fabric is not rigid. It behaves differently from metal, plastic or wood. A fabric piece bends, stretches, slips, folds and changes shape during handling.

1. Fabrics Are Limp

Fabrics bend in many directions. They do not remain fixed like a sheet of metal. This makes it difficult to design jigs, fixtures and automatic equipment for many sewing operations.

For example, while joining a sleeve to an armhole, the operator has to control curves, ease, seam allowance and fabric movement at the same time. This type of operation is difficult to fully mechanise.

2. Fabrics Vary in Extensibility

Different fabrics stretch differently. Some fabrics have very little extensibility, while knitted fabrics or stretch fabrics may extend considerably.

A minimum amount of yarn and fabric extensibility helps the sewing needle penetrate the fabric properly. If the extensibility is too low, sewing may become difficult. If the extensibility is too high, the fabric may distort during stitching.

3. Fabrics Vary in Thickness

Fabric thickness also affects garment manufacturing. A fine voile fabric, a denim fabric, a wool coating fabric and a quilted fabric cannot be handled in the same way. Seam formation, needle selection, thread selection, feed mechanism and pressing conditions all depend on fabric thickness.

4. Sewing Must Match the Fabric Behaviour

The method of joining must be compatible with the flexibility, drape and handle of the fabric. A garment seam should not only hold two fabric pieces together; it should also move with the fabric.

This is why sewing has remained the most widely used method of joining garments. Mechanically, a stitch is one of the few joining methods whose flexibility comes close to the flexibility of fabric itself.

Textile concept:
A good garment seam should be strong, but it should not make the fabric unnecessarily stiff. The seam must support the garment without spoiling its drape and handle.

Cutting Room Mechanisation

While sewing is difficult to fully automate, cutting room mechanisation is more practical and is widely used in many garment factories. This is because cutting deals with fabric in layers before garment components are separated for stitching.

In the cutting room, activities may include:

  • Fabric spreading
  • Marker planning
  • Manual or automatic cutting
  • Numbering and bundling
  • Sorting garment components

Modern garment factories may use computerised marker making, automatic spreading machines and automatic cutting machines. These technologies help reduce fabric wastage and improve cutting accuracy.

Why Cutting Is Economically Important

Cutting is very important because fabric is usually the largest cost component in a garment. In many garments, material cost forms a major part of the total cost.

Therefore, even a small saving in fabric consumption can have a large impact on profitability. This is why marker efficiency, lay planning and cutting accuracy are very important in garment manufacturing.

Area Main Concern Why It Matters
Cutting room Material utilisation Fabric is a major cost, so wastage must be controlled.
Sewing room Labour productivity Sewing depends heavily on operator skill and handling time.
Finishing section Appearance and quality Pressing, checking and packing influence final garment presentation.

Difference Between Cutting and Sewing Activities

Cutting and sewing are both essential, but they are very different in nature.

Cutting Sewing
Can be mechanised more easily. More difficult to automate fully.
Main concern is fabric saving and accuracy. Main concern is operator skill, quality and productivity.
Fabric is handled in layers. Fabric components are handled individually or in small assemblies.
Marker planning can improve material utilisation. Workplace design can improve handling efficiency.

Conclusion

The clothing industry is a unique industry because it must respond quickly to fashion changes while still depending heavily on human skill. The central process of garment manufacture is sewing, and sewing remains labour intensive because fabric is limp, flexible, extensible and variable in thickness.

At the same time, some areas such as cutting can be mechanised more easily because fabric can be handled in layers and material saving can be calculated systematically.

For a textile or fashion student, the most important understanding is this: garment manufacturing is not only about stitching. It is about managing fabric behaviour, labour skill, production flow, material cost and market speed together.

Key takeaway:
The garment industry remains labour intensive not because machines are unavailable, but because fabric is a difficult material to control automatically.

Tuesday, 2 October 2007

Textile Finishing



Textile Finishing: Meaning, Classification, Pre-Treatments, Resins and Important Finishes




Textile finishing is one of the most important stages in textile manufacturing. A fabric may be beautifully woven, knitted, dyed or printed, but it is the finishing process that finally decides how the fabric will look, feel and perform in actual use.

In simple terms, finishing refers to the various processes and treatments given to a fabric after it has been made and coloured. These processes prepare the fabric for its intended end use. A finish may make the fabric softer, stiffer, shrink-resistant, water-repellent, crease-resistant, flame-resistant, more lustrous, or more comfortable to wear.

A saree, shirt fabric, blanket, suiting material, workwear fabric or curtain material may all require different finishes because their end uses are different. Therefore, finishing is not just a decorative process; it is a functional and commercial necessity in textiles.

What Is Textile Finishing?


Finishing is the final processing of cloth after weaving or knitting and after dyeing or printing. Its purpose is to make the fabric suitable for the use for which it is intended.

For example, a fabric may be finished to become shrinkproof, softer in handle, stiffer and more formal, water-repellent, crease-resistant, flame-resistant, soil-resistant, more lustrous, more compact, warmer or more insulating.

In apparel retail, finishing often becomes a silent selling point. A customer may not know the technical name of a finish, but they immediately notice softness, shine, fall, crease recovery, warmth, or stiffness.

Classification of Textile Finishes

Textile finishes may be classified in several ways. Different people in the textile value chain look at finishing from different perspectives.

Designers, merchandisers and salespeople usually classify finishes according to how they affect the consumer experience. Textile chemists and processing experts classify them according to the method of application. Another useful classification is based on how long the finish lasts.

1. Aesthetic and Functional Finishes

From the point of view of the final product, textile finishes are commonly divided into aesthetic finishes and functional finishes.

Aesthetic Finishes

Aesthetic finishes improve the appearance or hand feel of the fabric. They may make the fabric smoother, softer, shinier, crisper, fuller, more lustrous or more decorative.

Examples include calendering, napping, shearing, glazing and embossing.

Functional Finishes

Functional finishes improve the performance of the fabric under specific conditions of use. These may make the fabric crease-resistant, flame-resistant, water-repellent, anti-static, antiseptic or soil-releasing.

For example, a hospital fabric may require antiseptic finishing, a workwear fabric may need soil release finishing, and a curtain fabric may require flame-retardant treatment.

2. Chemical and Mechanical Finishes

From the processing point of view, finishes are also classified as chemical finishes and mechanical finishes.

Chemical Finishes

Chemical finishes involve the application of chemicals to change or improve fabric properties. Resin finishing, crease-resistant finishing, flame-resistant finishing, antiseptic finishing and soil release finishing are examples.

These are also called wet finishes because they usually involve chemical baths, padding, curing or other wet-processing methods.

Mechanical Finishes

Mechanical finishes are produced mainly by physical action rather than chemical reaction. Calendering, shearing, napping and fulling are examples.

These are also called dry finishes, although some processes may involve moisture, heat or pressure.

3. Classification Based on Permanence

Textile finishes are also classified according to how long they remain effective.

Type of Finish Meaning Example Understanding
Permanent finish Usually involves a lasting chemical or structural change in the fibre or fabric. Mercerization of cotton
Durable finish Lasts through much of the life of the article, but gradually diminishes with cleaning. Durable press or some resin finishes
Semi-durable finish Lasts through several launderings or dry cleanings. Some anti-static finishes
Temporary finish Removed or greatly reduced after the first washing or dry cleaning. Starch-like stiffening finishes

This classification is very important for buyers, merchandisers and consumers. A finish that looks good in the showroom but disappears after one wash can create customer dissatisfaction.

Pre-Treatment Processes

Before finishing, fabrics usually undergo pre-treatment processes. These are cleaning operations designed to remove impurities, oils, waxes, dirt, added chemicals and other materials that may have entered the fabric during fibre preparation, spinning, weaving or knitting.

Pre-treatment is necessary because dyeing, printing and finishing cannot be properly carried out on an unclean fabric.

In cotton, cotton blends, silk and man-made fibres, these cleaning treatments are often known generally as boil-off. In woollen and worsted fabrics, the process is known as scouring.

Pre-treatment may look like a background process, but it has a major effect on the quality of the final textile. Poor pre-treatment may lead to uneven dyeing, poor finishing, patchy appearance, lower absorbency and customer complaints.

The Role of Resins in Textile Finishing

Resins are an important group of chemicals used in many textile finishes. They are especially common in the finishing of cellulosic and cellulosic blend fabrics such as cotton, rayon and polyester-cotton blends.

Resins can significantly affect the hand, drape and physical characteristics of fabrics. They can make a fabric stiffer, more stable, crease-resistant or shrink-resistant. However, they may also reduce some desirable properties such as absorbency, tear strength and abrasion resistance.

Effects of Resins on Fabric

Resins can add stiffness and create a firm hand. This is useful in fabrics where body, crispness or structure is desired.

They can stabilize a fabric in the shape in which it is cured. For example, a fabric cured in a smooth condition tends to return to that smooth condition after wrinkling. Similarly, a garment cured with a crease can retain that crease.

Resins can also stabilize yarns in the fabric and help resist shrinkage during laundering.

However, there are disadvantages. Resin-treated fabrics may become less absorbent, which means they dry faster but may feel less comfortable in hot and humid weather. Resin finishing may also reduce abrasion resistance, breaking strength and tear strength, especially in cellulosic fibres. In some cases, this strength reduction can be considerable.

Some resins may also produce an unpleasant odour, often described as fish-like or formaldehyde-like. This odour generally reduces after airing or laundering. Another problem is that resins may attract oily soils, which is why soil release finishes are often applied along with resin finishes.

Important Textile Finishes

1. Anti-Static Finishes

Anti-static finishes are applied to reduce or eliminate static electricity in textiles. Static is a common problem in synthetic fabrics, especially in dry weather. It may cause garments to cling to the body, attract dust, or produce small electric shocks.

Anti-static finishes work by absorbing small amounts of moisture from the atmosphere. This reduces the dryness of the fabric and helps dissipate static charges.

However, many anti-static finishes are only semi-durable. They may wash out or wear off after several launderings or dry cleanings. More permanent anti-static effects are possible in man-made fibres that have been specially modified for this purpose.

2. Antiseptic Finishes

Antiseptic finishes are chemical treatments that inhibit bacterial growth. They are useful in products where odour, hygiene and skin comfort are important.

These finishes may be used in shoe linings, luggage materials, underwear fabrics, socks, sportswear, medical textiles and similar products.

They are generally low in cost, easy to apply, and durable to laundering and dry cleaning. In modern textile marketing, these finishes are often connected with terms such as antibacterial, antimicrobial, odour control or hygiene finish.

3. Calendering

Calendering is a mechanical finishing process. It is not one single finish but a group of finishes produced by different calendering machines and settings.

A calender consists of two or more large rotating cylindrical rollers, usually heated and placed under pressure. The fabric passes between these rollers. Depending on the roller surface, pressure, heat, speed and fabric type, different effects can be produced.

Calendering can improve smoothness, lustre, compactness and surface appearance.

Type of Calendering Effect
Simple calendering Smoothens and flattens the fabric surface.
Glazing calendering Produces a polished or glossy effect.
Embossed calendering Produces raised or depressed patterns.
Moiré calendering Produces a watered or wavy appearance.
Schreiner calendering Produces high lustre through fine engraved lines.

In sarees and dress materials, calendering can influence shine, fall and surface appeal.

4. Crease Resistant Finishes

Crease resistant finishes are commonly known as CRF finishes. They are mainly used on cotton, rayon and linen because these fibres wrinkle easily.

CRF finishes are usually resin finishes. The fabric is saturated with resin and then cured at high temperature. The treatment makes the fabric stiffer, less absorbent and more resistant to wrinkling.

The main advantage is easy-care performance. Garments remain neater and require less ironing.

However, there are disadvantages. Resin treatment can reduce tensile strength and abrasion resistance, particularly in cellulosic fibres. Therefore, the finisher must balance wrinkle resistance with fabric strength and comfort.

Most crease resistant finishes are durable.

5. Flame Resistant Finishes

Flame resistance can be achieved in two ways. The first method is to use fibres that are naturally or inherently flame resistant. The second method is to apply flame resistant finishes to fabrics.

Flame resistant finishes are important for curtains, upholstery, children’s sleepwear, protective clothing, industrial textiles, uniforms and public-use fabrics.

However, flame retardant finishes may have certain limitations. They may stiffen the fabric, reduce drapability, cause strength loss, lose effectiveness after laundering, or become less effective when washed with bleach, soaps or water softeners.

This is why flame-resistant textile development always involves a balance between safety, comfort, durability and appearance.

6. Fulling

Fulling is a permanent finish used on wool fabrics. It is also known as milling or felting.

The process is a carefully controlled scouring or laundering treatment that induces felting shrinkage in wool fabrics. As a result, the fabric becomes smoother, more compact and more closely structured.

After fulling, the yarns become more tightly embedded in the fabric. Woollen fabrics are often heavily fulled to produce warmth, body and compactness.

This finish is especially important in blankets, coats, woollen suiting and traditional wool fabrics.

7. Mercerization

Mercerization is one of the most important cotton finishes.

It is a permanent finish that improves cotton in several ways. It increases lustre, improves strength, enhances dye affinity, produces brighter shades and improves hand feel. Mercerized cotton may also require less dye to achieve the same depth of shade.

The process involves treating cotton yarn or fabric under tension with cold, concentrated sodium hydroxide solution.

Mercerization can be applied to yarns and fabrics, but not to loose fibres.

In retail language, mercerized cotton is often associated with a smoother, shinier, stronger and more premium cotton fabric.

8. Napping

Napping is a mechanical finish in which woven or knitted fabrics are passed against rotating wire-covered brushes. These brushes raise fibres from the fabric surface, creating a soft, fuzzy surface.

Napped fabrics have a softer hand and provide better insulation because the raised fibres trap air.

This is why napping is widely used in blankets, flannels, sleepwear and winter clothing.

However, the durability of the nap depends on the fibre. Cotton and rayon napped fabrics may lose their raised surface more quickly because these fibres have lower resilience. The nap may flatten with use, though it can be partly restored by brushing.

9. Plissé Finish

Plissé is both the name of a finish and the name of the fabric produced by that finish.

It is a permanent finish usually produced on cotton using sodium hydroxide. Unlike mercerization, the fabric is not held under tension.

The sodium hydroxide is printed on the fabric in paste form. The treated areas shrink, while untreated areas do not. This difference in shrinkage produces a puckered or crinkled effect.

Plissé fabrics are often used in summer garments because the puckered surface keeps parts of the fabric away from the skin, improving air circulation and comfort.

10. Shearing

Shearing is a process used to cut off surface fibres from fabric.

It is especially important after napping because it makes the raised surface more uniform. Cut pile fabrics are also sheared to create an even pile height.

Shearing improves appearance, smoothness and uniformity. In pile fabrics, it helps create a neat and controlled surface.

11. Soil Release Finishes

Soil release finishes make it easier to remove soil, especially oily soil, during ordinary home laundering.

These finishes work by making fibres more absorbent or hydrophilic. This improves wettability, allowing water and detergent to penetrate the fabric more effectively and remove dirt.

Soil release finishes are often applied along with resin finishes, especially because resin-treated fabrics may attract oily soils.

They are commonly used in workwear, tablecloths, slacks, skirts and durable press fabrics. Many soil release finishes are durable through 40 to 50 launderings.

Apart from soil removal, these finishes may also improve anti-static properties, fabric drapability and comfort in hot weather.

Textile Finishing and End Use


The choice of finish depends on the final use of the fabric.

End Use Useful Finishes
Sarees and dress materials Calendering, mercerization, softening, embossing
Workwear Soil release, crease resistance, flame resistance
Blankets and winterwear Napping, fulling
Children’s wear Flame resistance, soft finish
Sportswear Anti-static, antiseptic, moisture management
Table linen Soil release, crease resistance
Cotton shirting Mercerization, crease resistance, soft finish
Woollen fabrics Fulling, shearing, brushing

This makes finishing a bridge between textile manufacturing and consumer satisfaction. The same base fabric can become suitable for different markets depending on the finish applied.

Conclusion

Textile finishing gives fabric its final identity. It can change the appearance, hand, comfort, durability, safety and performance of a textile. Some finishes are mainly aesthetic, while others are functional. Some are temporary, while others are permanent.

For textile students, finishing helps explain why two fabrics made from the same fibre may behave very differently. For merchandisers and retailers, finishing is an important selling point. For consumers, it determines comfort, care, durability and satisfaction.

In short, finishing is not merely the last step in textile production. It is the step that converts cloth into a usable, desirable and market-ready textile product.



Textile Printing-1



Textile Printing Methods: Roller, Screen, Rotary Screen and Heat Transfer Printing

Printing has often been described as dyeing in a localized, patterned design. In dyeing, colour is usually applied uniformly to the whole fabric, yarn, fibre, or garment. In printing, the colour is applied only to selected areas of the fabric to create motifs, repeats, borders, buttas, stripes, florals, paisleys, checks, or other decorative effects.

Textile printing uses many of the same dyes or pigments that are used in textile dyeing. The same principles of dye selection, fibre affinity, colour fastness, and shade performance apply to printing as they do to dyeing.

Printing and Dyeing: What Is the Difference?

In dyeing, dyes or pigments are generally used in a water bath solution. The textile material is immersed in the dye bath so that the colour can penetrate the fibre, yarn, or fabric.

In printing, however, the colour must remain exactly where the design requires it. Therefore, the dyes or pigments are thickened with gums or starches so that the print does not spread, wick, or flow outside the design area. This thickened colour mixture is called print paste.

The print paste is generally thick, almost like heavy buttermilk. This thickness helps the design remain sharp and prevents bleeding of the printed pattern.

Why All Dyes Cannot Be Used for Printing

Although printing and dyeing use similar colouring substances, not every dye used for dyeing is suitable for printing. A dye may fail in printing because of several reasons.

Some dyes do not dissolve properly in the print paste. Some give low colour yield when printed. Others may not remain stable in the thickened paste. If the dye is not stable, the shade may change, weaken, or become uneven during printing, drying, steaming, or curing.

Therefore, a successful printing dye must not only have affinity for the fibre, but must also perform well inside a printing paste.

Methods of Textile Printing

There are several methods used for printing textiles. Among them, two have been of major commercial importance: roller printing and screen printing. A third method, heat transfer printing, is also important, though more limited in its application.

Other traditional or less widely used printing methods include block printing and batik printing. These methods are very important from a craft, design, and cultural point of view, although they are not used as widely in large-scale commercial textile production.

The main printing methods discussed here are:

  1. Roller printing
  2. Hand screen printing
  3. Automatic screen printing or flat bed printing
  4. Rotary screen printing
  5. Heat transfer printing

1. Roller Printing

Roller printing is one of the oldest and most important machine printing methods. It may be compared to newspaper printing because the design is transferred through engraved rollers. It is a high-speed process and can produce more than 6000 yards of printed fabric per hour. For this reason, it is also known as machine printing.

In roller printing, the design is engraved on copper rollers, also called copper engraved cylinders. These roller engravings must match the creative sketch prepared by the textile designer. A separate engraved cylinder is required for each colour in the print.

For example, if a fabric has a four-colour design, four separate engraved rollers are required. The size of the engraved cylinder depends on the printing machine and the design repeat.

How Roller Prints Are Made

In roller printing, the engraved copper roller rotates and comes into contact with a colour furnisher. The colour furnisher works somewhat like a paint roller used in house painting. It picks up print paste from the colour box and transfers it to the surface of the engraved copper roller.

The entire surface of the roller becomes covered with print paste. Then the roller comes into contact with a doctor blade. This steel blade works like a squeegee. It scrapes off the print paste from the smooth surface of the roller but leaves the paste inside the engraved portions.

The fabric is then guided between the cylinder roller and the engraved copper roller. Pressure at the point of contact transfers the print paste from the engraved area onto the cloth. In this way, the pattern is printed on the fabric.

As the engraved roller continues to rotate, it also comes into contact with a lint doctor. This blade removes any lint that may have been picked up from the fabric being printed.

If additional colours are required, the same process is repeated with additional engraved rollers, colour boxes, doctor blades, and related mechanisms. The fabric usually makes only one pass through the roller printing machine. The colours do not usually become smudged because the pressure of the roller squeezes the print paste into the fabric and the surface colour dries quickly.

After printing, the fabric is immediately dried so that it can be handled without smudging. If dyes are used, the fabric is generally steamed so that heat and moisture help to set the colour. If pigments are used, the fabric may be cured in a dry heat oven at temperatures up to about 400°F.

What Is Back Grey?

In roller printing, a fabric called back grey moves through the printing machine along with and behind the fabric being printed. Its function is to absorb excess print paste that may strike through the printed fabric and stain the cylinder roller cover.

The back grey is washed and reused again and again. Over time, it develops a dull grey appearance, which gives it the name “back grey.”

Advantages of Roller Printing

Roller printing is best suited for long production runs of the same pattern. It is especially useful for fine-line patterns and paisley prints. It can produce half-tones and fall-on effects.

A half-tone is a gradual shading from light to dark in the same colour. A fall-on effect occurs when two colours overlap and produce a third colour. This makes it possible to achieve a three-colour appearance with two rollers or two screens.

Roller printing can be used successfully on woven fabrics. Knitted fabrics may also be printed, but they require special handling.

Limitations of Roller Printing

Roller printing is not economical for short production runs because engraving the rollers is expensive. Pattern changeovers take time, and production delays may occur when new patterns have to be prepared.

Another limitation is repeat size. The pattern repeat is limited by the machine and cylinder size. In many cases, the repeat is limited to about 16 inches for apparel patterns and about 22 inches for home furnishing fabrics.

2. Screen Printing

Screen printing is a method in which print paste is forced through a closely meshed screen onto the fabric. The screen is mounted in a wooden or metal frame and placed in contact with the fabric.

The design is created by blocking certain portions of the screen. The blocked areas do not allow print paste to pass through. The open areas allow the print paste to pass and form the printed design.

The paste is pushed through the screen by a squeegee, which is a rubber-edged implement used for spreading or forcing liquid-like material across a surface.

There are three important methods of screen printing:

  1. Hand screen printing
  2. Automatic screen printing or flat bed printing
  3. Rotary screen printing

Although these methods differ in machinery and speed, the basic principle remains the same: the design is created by allowing print paste to pass only through selected open areas of the screen.

3. Hand Screen Printing

Hand screen printing is carried out commercially on long printing tables, sometimes up to 60 yards in length. The fabric is spread smoothly on the table, whose surface is first coated with a light tack adhesive. This helps hold the fabric in place during printing.

The print operators move the screen frames by hand along the length of the table. The fabric is printed one frame at a time until the complete length is printed.

Each screen frame carries one colour of the design. Therefore, a three-colour print requires three separate screen frames and three separate applications on the fabric.

The rate of production in hand screen printing is around 50 to 90 yards per hour.

Advantages of Hand Screen Printing

Hand screen printing is best suited for low yardage samples, exclusive designs, and limited quantity production. It is useful when the design is special, experimental, or not required in very large quantities.

Large repeat sizes, up to about 120 inches, are possible. Wet-on-dry print effects can also be produced.

Hand screen printing gives better colour definition than roller printing because it allows a heavier lay-on of colour. It is adaptable to woven and knitted constructions. Screens can be prepared quickly, and pattern changeover is relatively rapid.

It also allows printing of cut garment parts and small items such as towels, scarves, panels, and accessories.

Limitations of Hand Screen Printing

Hand screen printing is slow compared to machine printing. It is uneconomical for large production yardage.

It is also not suitable for half-tone designs, fine-line paisley prints, and lengthwise stripe designs. Since it depends heavily on manual handling, skill and accuracy are very important.

4. Automatic Screen Printing or Flat Bed Printing

Automatic screen printing, also called flat bed printing, follows the same principle as hand screen printing, but the process is automated.

Instead of spreading the fabric on a long table and moving the screens manually, the fabric moves on a wide rubberized belt. The fabric moves to the screen, stops for the automatic squeegee action, and then moves again to the next screen.

This makes flat bed printing an intermittent process, because the fabric stops and starts during printing.

The production rate of automatic screen printing is about 500 yards per hour. It is mainly used for printing whole rolls of fabric.

Advantages of Automatic Screen Printing

Automatic flat bed printing allows large repeat sizes, up to about 240 inches. It gives better colour definition than roller printing and is equal to hand screen printing in colour clarity.

It is adaptable to woven and knitted fabrics. Design changeover is relatively rapid, and it gives very good machine registration.

This method is useful where good quality screen printing is required in roll form, but production needs to be faster than hand screen printing.

Limitations of Automatic Screen Printing

The cost of screen preparation and special mountings is higher than hand screen printing. It is not suitable for very low yardage production.

Half-tone designs and fine-line paisley prints are not possible. Lengthwise stripes are also difficult or not possible in this method.

5. Rotary Screen Printing

Rotary screen printing is different from hand screen and flat bed screen printing in several important ways. Unlike flat bed printing, rotary screen printing is continuous. In this respect, it is closer to roller printing.

In rotary screen printing, the fabric moves on a wide rubber belt under rotating cylindrical screens. These screens are seamless and perforated and may be made of metal or plastic.

Rotary screen printing is the fastest form of screen printing. It can produce around 2500 to more than 3500 yards per hour.

The largest rotary screens have a circumference of about 40 inches, so the maximum pattern repeat is usually about 40 inches.

Advantages of Rotary Screen Printing

Rotary screen printing allows repeat sizes over 40 inches, which are larger than many roller printing repeats but smaller than flat screen repeats.

Lengthwise stripe effects and fall-on designs are possible. It is adaptable to woven and knitted fabrics.

Rotary screen prints generally have cleaner and brighter colours than roller prints. They also give excellent colour definition, although not as much as flat screen printing.

Design changeover is faster than roller printing. Rotary printing is efficient for long runs as well as moderately small runs of around 1000 yards.

Limitations of Rotary Screen Printing

Fine-line paisley prints are not possible. Half-tone designs are not as effective as in roller printing.

Another limitation is that rotary screens do not last as long as engraved rollers. Therefore, screen life becomes an important production consideration.

6. Heat Transfer Printing

Heat transfer printing is also known as thermal transfer printing.

In this method, the design is first printed on paper using printing inks containing disperse dyes. This printed paper is known as transfer paper. The paper is stored until the textile printer or converter is ready to transfer the design onto fabric.

When the fabric is to be printed, the transfer paper and fabric are brought together face to face and passed through a heat transfer printing machine. The machine applies heat, usually around 400°F.

At this high temperature, the disperse dye on the printed paper sublimates and transfers onto the fabric. The process is somewhat similar to decal transfer.

Heat transfer printing is relatively simple and does not require the same level of expertise as roller printing or rotary screen printing.

Why Disperse Dyes Are Used in Heat Transfer Printing

Disperse dyes are used because they can sublime under heat. Sublimation means the dye changes into vapour and transfers from the paper to the textile material.

Since disperse dyes have affinity for certain synthetic fibres, heat transfer printing is limited to fibres such as acetate, acrylics, polyamides such as nylon, and polyester.

Advantages of Heat Transfer Printing

Heat transfer printing can produce bright, sharp, and clear fine-line designs. It can be used for cut garment parts and small items.

It is adaptable to both long and short yardage runs. Pattern changeover is rapid. The installation is relatively simple and requires low investment compared to some conventional printing methods.

Another advantage is that steamers, washers, dryers, and other post-treatment equipment are generally not required. The actual printing process takes only a few seconds, and heat setting can also be accomplished during the same process.

Limitations of Heat Transfer Printing

The preparation of transfer paper can create lead-time problems, especially in high-fashion markets where speed is important.

The method is generally limited to fabrics containing at least 50% man-made fibres. Cellulosic fibres such as cotton and protein fibres such as wool and silk cannot be printed effectively by this method.

Another limitation is that it is more suitable for printing over pastel shades or prepared production yardage. It may not completely cover a darker original fabric colour.

Comparison of Textile Printing Methods

Printing Method Best Suited For Main Advantages Main Limitations
Roller Printing Long production runs High speed, fine-line designs, paisleys, half-tones Expensive engraving, limited repeat size, uneconomical for short runs
Hand Screen Printing Low yardage and exclusive designs Large repeats, good colour definition, flexible design change Slow production, not suitable for large yardage
Automatic Screen / Flat Bed Printing Whole rolls of fabric Large repeats, good registration, better speed than hand screen Not suitable for low yardage, limited for half-tones and fine paisleys
Rotary Screen Printing Long and moderately small runs Continuous printing, bright colours, good speed, adaptable to woven and knitted fabrics Fine-line paisleys difficult, screens do not last as long as rollers
Heat Transfer Printing Synthetic fabrics and small items Sharp designs, low investment, quick changeover, no major post-treatment Limited to certain fibres, transfer paper lead time, poor coverage on dark grounds

Printed Fabric Imperfections

Printed fabrics may show certain defects or imperfections. These may arise due to faulty printing procedures, improper fabric preparation before printing, or defects in the fabric itself.

Since textile printing is similar to dyeing in many respects, many imperfections found in dyed fabrics may also be found in printed fabrics.

Colour Drag

Colour drag occurs when the colour of the print smears or smudges because it rubs against another object before it becomes dry.

Colour Splatter

Colour splatter occurs when the print paste is thrown or splattered onto the fabric surface instead of being placed only on the intended design area.

Fuzzy Pattern

A fuzzy pattern occurs when the edges of the printed design are not sharp and clear. Instead, the edges appear blurred or fuzzy.

This is often caused by improper singeing or by print paste that has not been thickened properly.

Off-Register

Off-register occurs when printing rolls or screens are not properly aligned. As a result, different parts of the pattern do not meet correctly.

This defect is also called out-of-fit or out-of-register.

Stop Mark

A stop mark is a colour streak across the fabric. It occurs when the printing machine is stopped during the printing process and then started again.

Tender Spots

Tender spots are weakened areas in printed fabrics. Sometimes one or more colours in the print may weaken the fabric in the areas where they are printed.

This is usually due to excessive use of injurious chemicals in the print paste. Tender spots may also be found in discharged areas of discharge prints.

Practical Note for Textile Students and Merchandisers

The printing method is not selected randomly. It depends on the type of design, repeat size, fabric construction, fibre content, production quantity, colour sharpness required, cost, and delivery time.

For example, if a mill needs a very long production run with fine paisley designs, roller printing may be suitable. If the order is small and exclusive, hand screen printing may be preferred. If high-speed screen printing is needed, rotary screen printing may be more practical. If the fabric is polyester and the design requires sharp colour effects, heat transfer printing may be considered.

In fashion and saree production, the choice of printing method affects not only cost but also design clarity, colour depth, repeat size, hand feel, and final market appeal.



Conclusion

Textile printing is the art and science of applying colour in selected areas to create patterns on fabric. It is closely related to dyeing, but printing requires the use of thickened print paste so that the design remains sharp and controlled.

Roller printing, screen printing, rotary screen printing, and heat transfer printing each have their own advantages and limitations. Roller printing is fast and suitable for long runs. Hand screen printing is flexible and good for exclusive designs. Flat bed printing gives large repeats and good registration. Rotary screen printing combines speed with screen-print quality. Heat transfer printing is simple and effective for synthetic fibres.

A good understanding of printing methods helps textile students, designers, merchandisers, production teams, and buyers make better decisions about fabric development, cost, design suitability, and quality control.

Printing Method Important Features and Advantages Limitations and Disadvantages
Roller Best suited for long production runs of same pattern. Best method for fine-line patterns and paisley prints. Can produce half-tones and fall-on effects. A half-tone is a gradual shading from light to dark in the same colour. A fall-on is two colours of overlapping pattern, which results in a third colour. It is thus possible to achieve a three-colour print with two rollers or two screens. Can print woven fabrics. Knitted fabrics require special handling. Machine size of pattern repeat limited to 16-inch maximum for apparel patterns and 22 inches for home furnishings. Uneconomical for short runs. Long production delays in pattern changeovers. Engraving is expensive.
Hand Screen Best method for low yardage samples, exclusive, limited quantity designs. Large repeat sizes, up to 120 inches possible. Wet-on-dry print effects possible. Better colour definition than roller print due to heavier lay-on of colour. Adaptable to all woven and knitted constructions. Rapid preparation of screens and rapid pattern changeover possible. Ability to print cut garment parts and small items, towels, scarves etc. Half-tone designs not possible. Fine-line paisley prints not possible. Lengthwise stripe designs not possible. Slow production. Uneconomical for large production yardage.
Automatic Screen
(Flat Bed)
Large repeat size, up to 240 inches possible. Better colour definition than roller print; equal to hand screen. Adaptable to all woven and knitted constructions. Rapid changeover of designs possible. Best machine registration. Cost of screen preparation and special mountings more costly than hand screen. Not adaptable to low yardage. Half-tone designs not possible. Fine-line paisley prints not possible. Lengthwise stripes not possible.
Rotary Screen Over 40-inch repeat size possible; larger than roller printing, but smaller than flat screen methods. Lengthwise stripe effect possible. Fall-on designs possible. Adaptable to all woven and knitted constructions. Cleaner and brighter colours than on roller prints. Excellent colour definition, but less than flat screen methods. Rapid changeover of designs possible. Efficient for long runs and moderately small, 1000 yards runs. Fine-line paisley prints not possible. Half-tone designs not as effective as roller printing. Screens do not last as long as rollers.
Heat Transfer Produce bright, sharp, clear fine-line designs. Ability to print cut garment parts and small items. Adaptable to long and short yardage runs. Rapid pattern changeover possible. Simple, low-investment installation possible. Streamers, washers, dryers etc. not required; no post-treatments. Fewest seconds of all print processes. Heat setting also accomplished. Lead time for paper preparation can cause problems in high-fashion markets. Limited to fabrics having minimum 50% man-made fibres. Cellulosic and protein fibres cannot be printed. Overprint only on pastels or production yardage. Else will not completely cover the original cover.

Monday, 1 October 2007

Textile Dyeing -3



Dyeing and Types of Dyeing in Textiles





Dyeing is one of the most important processes in textile manufacturing. It is the process by which colour is applied to textile materials such as fibres, yarns, fabrics, or garments. Dyeing can be carried out at different stages of textile production, depending on the type of fabric, design requirement, end use, cost consideration, and the depth of colour penetration required.

In textile manufacturing, dyeing may be done at the fibre stage, yarn stage, fabric stage, or garment stage. Each stage has its own advantages and limitations. Generally, dyeing at an earlier stage gives better colour penetration and uniformity, while dyeing at a later stage allows greater flexibility in fashion, design, and market response.

Stages of Dyeing

Textile materials may be dyed in the following stages:

  1. Fibre stage
  2. Yarn stage
  3. Fabric stage
  4. Garment stage
  5. Cross dyeing

The choice of dyeing stage depends on the final product. For example, if a fabric needs checks, stripes, plaids, or multicoloured woven designs, yarn dyeing is usually preferred. If the final colour decision has to be delayed until the garment is ready, garment dyeing may be used.




1. Fibre Stage Dyeing

Fibre stage dyeing means dyeing the fibre before it is spun into yarn. Since the dye is applied at the earliest stage, the colour penetration is usually very good.

Stock Dyeing

Stock dyeing refers to the dyeing of fibres, also called stock, before they are spun into yarn.

In this method, loose fibres are dyed first and then blended, carded, combed, and spun into yarn. This method is useful when a uniform colour is required throughout the yarn and fabric. It is also useful for producing heather effects or mixed-colour yarns, where fibres of different colours are blended before spinning.

Top Dyeing

A sliver of worsted, known as top, is sometimes dyed at the stage between fibre and worsted yarn.

Top dyeing is especially associated with wool and worsted spinning. In this process, the fibres have already been combed and arranged in a more parallel form, but they have not yet been spun into yarn. Dyeing at this stage gives good uniformity and is commonly used where high-quality yarns and fabrics are required.

2. Yarn Stage Dyeing

Yarn dyeing means dyeing the yarn before it is woven or knitted into fabric. This method is very important when the final fabric has to show patterns created by differently coloured yarns.

The main reason for dyeing yarn is to manufacture plaids, stripes, checks, dobby effects, jacquard effects, and other multicoloured designs.

In many traditional and fashion textiles, yarn dyeing plays a very important role. For example, checks in shirting fabrics, stripes in sarees, borders in woven fabrics, and many ikat-type effects depend on yarn-level colour planning.

Skein Dyeing

Skein dyeing consists of immersing large, loosely wound hanks of yarn into dye vats specially designed for this purpose.

In this method, yarn is not tightly wound. It remains in loose hank form, allowing the dye liquor to move freely around the yarn. Because of this, skein dyeing can give soft handle and good colour penetration. However, it is more labour-intensive and slower than some other yarn dyeing methods.

Package Dyeing

In package dyeing, about a pound of yarn is wound on a small perforated spool or tube called a package.

Many such spools fit into a dyeing machine. The dye bath is circulated through the packages. The flow of the dye liquor alternates from the centre to the outside and then from the outside to the centre of the package.

This alternating flow helps in achieving more uniform dyeing. Package dyeing is widely used in modern textile mills because it is efficient, compact, and suitable for large-scale yarn dyeing.

Beam Dyeing

In beam dyeing, an entire warp beam is wound on a perforated cylinder. This cylinder is then placed in the beam dyeing machine.

As in package dyeing, the flow of the dye bath alternates through the yarn. Beam dyeing is mainly used for warp yarns. Since the warp is already wound on a beam, it can be dyed in a form closer to its weaving preparation stage.

This method is useful when the warp yarn needs to be dyed uniformly before weaving.

3. Fabric Stage Dyeing

Fabric dyeing means dyeing the textile after it has been woven, knitted, or otherwise constructed into fabric. This is one of the most common methods of dyeing.

Fabric dyeing is suitable when the entire fabric is required in one solid colour. It gives flexibility because the manufacturer can first produce greige fabric and then dye it according to market demand.

Common methods of fabric dyeing include:

Beck Dyeing

In beck dyeing, the fabric is dyed in rope form in a large dye vessel. The fabric moves continuously through the dye bath. This method is suitable for many kinds of fabrics, especially where gentle movement is required.

Jet Dyeing

In jet dyeing, the fabric is circulated through the dyeing machine by the force of the dye liquor. This method is commonly used for synthetic and blended fabrics. It is faster and suitable for fabrics that need controlled dyeing conditions.

Pad Dyeing

In pad dyeing, the fabric is passed through a dye solution and then squeezed between rollers to remove excess dye liquor. The dye is then fixed by further processing such as steaming, heating, or chemical treatment.

Pad dyeing is commonly used in continuous dyeing processes and is suitable for large-scale production.

Beam Dyeing

In fabric beam dyeing, fabric is wound on a perforated beam and dye liquor is circulated through it. This method is useful for fabrics that should not be subjected to too much mechanical movement.

4. Garment Dyeing

Garment dyeing means dyeing the textile after it has already been stitched into a garment.

In this method, the garment is first made in an undyed or prepared fabric, and then the finished garment is dyed. Garment dyeing is useful when manufacturers want to respond quickly to fashion trends or market demand.

It allows the decision of colour to be postponed until the final stage. This can reduce the risk of producing large quantities of fabric in colours that may not sell well.

However, garment dyeing requires careful control. The thread, trims, buttons, zippers, labels, and fabric must all be compatible with the dyeing process. Shrinkage, seam puckering, uneven dyeing, and colour variation may occur if the process is not properly managed.

5. Cross Dyeing

Cross dyeing is a special type of dyeing in which a yarn, fabric, or garment made with two or more kinds of fibres having different dyeing qualities is dyed in a single bath containing two different classes of dyes.

Each class of dye colours only one type of fibre. In this way, two different colours can be dyed in one dye bath. Alternatively, one type of fibre may be dyed while the other remains white.

For example, if a fabric is made from two fibres, such as polyester and cotton, dyes may be selected so that one dye colours the polyester and another dye colours the cotton. The result can be a two-tone or multicoloured effect from a single dyeing operation.

Cross dyeing is useful for producing novelty effects, mixed shade effects, checks, stripes, textured looks, and special fashion fabrics. It depends heavily on the difference in dye affinity between the fibres used.

Relationship Between Dyeing Stage, Cost, Fashion Flexibility, and Dye Penetration

The stage at which dyeing is done affects cost, flexibility, and colour penetration.

Dyeing at the fibre or yarn stage generally gives better colour penetration and is useful for high-quality or multicoloured woven designs. However, it may involve higher planning and inventory commitment.

Dyeing at the fabric or garment stage gives more flexibility because the colour decision can be taken later. This is closer to fashion demand and market response. However, dye penetration and uniformity may require greater care, especially in garment dyeing.

Comparison of Different Dyeing Stages

Dyeing Stage Main Advantage Common Use
Fibre dyeing Excellent colour penetration Wool, blends, heather effects
Top dyeing Uniform colour in worsted yarns Worsted fabrics
Yarn dyeing Required for checks, stripes, and plaids Shirtings, sarees, woven designs
Fabric dyeing Suitable for solid-colour fabrics General apparel fabrics
Garment dyeing Fashion flexibility and quick response Casual wear, fashion garments
Cross dyeing Two-tone or special colour effects Blended fabrics and novelty textiles

Conclusion

Dyeing can be carried out at several stages in textile manufacturing: fibre, top, yarn, fabric, or garment stage. Each method serves a different purpose. Fibre and yarn dyeing are preferred when deep penetration, uniformity, and multicoloured woven effects are required. Fabric dyeing is commonly used for solid-colour fabrics, while garment dyeing gives flexibility in fashion and inventory planning.

Cross dyeing is a special method that takes advantage of the different dyeing behaviour of different fibres. It allows two or more colour effects to be produced in one dye bath.

Thus, the method of dyeing is not chosen randomly. It depends on the fibre, yarn, fabric structure, design requirement, production cost, and final appearance desired in the textile product.

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