24 Textile Finishes

S. Karpagam Chinnammal

epgp books

 

 

 

 

Learning Objectives

 

  • To understand about fabric finishes and its objectives
  • Learn about the classification of finishes
  • To understand the fundamentals, techniques and application of different finishes to fabrics

1.    Introduction

 

In textile production the making of saleable and customer usable textile material is not accomplished just after weaving, knitting, dyeing or printing. Materials must undergo further process referred to as finishing. It is the ultimate stage of processing of the cloth, to make it suitable for its desired end use. The desired functional properties are imparted to the fabric through various physical and chemical treatments.

 

Finishing includes a single process or a series of processes which help to maintain or increase the value of the textile material. It makes the fabric more efficient. There are different types of finishing operations like making the fabric soft, stiff, wrinkle resistant, flame retardant, water proof, anti static or a combination of these.

 

2.    Definition

 

Treatments given to textile material to improve their appearance, feel and qualities/characteristics are referred to as textile finishes.

 

3. Object of finishing

 

The object of finishing is to

  • Make the fabric more appropriate for its end use
  • impart better appearance    like whiteness and luster to a fabric and enhance its looks
  • improve the drape , feel or handle, serviceability/utility of the fabric
  • improve the wearing qualities of fabric by making it anti static or crease resistant
  • impart special qualities for specific use like flame retardancy, antimicrobial finish etc
  •  provide desirable qualities to the fabric like dimensional stability, soil repellency etc
  • enhance the sale ability of the fabric
  • make up for faults in the original fabric
  • produce novelty effects eg organdie fabrics by parchmenting
  1. Classification of finishes

Textile finishes are classified in a number of ways.

Based on the function finishes are categorized as aesthetic finishes and functional finishes they are also called basic or special finishes respectively. Aesthetic finishes alter the appearance and/or hand (feel) of fabrics. Example. A thin fabric may be starched to increase its weight and shine. Calendering gives a neat look. A dull gray fabric is bleached to get a bright white colour. All these are aesthetic finishes. The functional finish improves the performance properties of a fabric as per the end use of the product for example

  • water proof finish makes fabrics water repellent for making umbrellas and     Tarpaulins
  • crease- resistant finish makes cotton / wool fabric wrinkle resistant.
  • fire proof finish prevents the burning of fabrics

Finishes are also classified as chemical finishes and mechanical finishes based on the application of finish. Chemical finish also called wet finish uses acids, alkalis, bleaches, resins and other chemicals to either change the appearance or property of fabric. Properties which are not possible by mechanical means can be imparted by chemical means. These finishes are usually durable and permanent. Examples are fireproof, Mercerisation etc. Chemical finish may be reactive type in which chemical reaction causes change in fiber eg. Mercerisation, Flame retardancy or deposition types in which substances are held on the fabric eg. Starch. Mechanical finish also called dry finish involves application of physical treatment ie friction, pressure, temperature and tension to the surface of fabric using machines. eg Napping, Shearing, calendaring etc. These finishes are either temporary or semi durable and are not long lasting.

Finishes are also categorized based on their period of effectiveness as permanent, durable, semi-durable and temporary.

 

Permanent finishes lasts the life of the fabric without any change in its effectiveness because it is usually a chemical process that changes the fiber structure e.g. Water proofing, fire proofing, etc.

  • Durable finishes usually last all through the life of the product, but efficiency diminishes with use. e.g. permanent pleats, wrinkle resistance, etc
  • Semi-durable finishes last through a number of launderings or dry cleanings and then removed e.g. bleaching.
  • Temporary finishes lasts only until the item is laundered or dry cleaned. e.g. starching and calendering .

Each finish may fall into one or more of the above categories. For example Desizing, scouring and bleaching are all basic finishes and are achieved using chemical finishes. Starching is a basic finish which is temporary. Singeing is a basic and mechanical finish. Mercerization, plisse are special finishes which are applied using chemicals and are permanent

 

5.    ROUTINE FINISHES

 

5.1.Desizing– is the removal of starch from gray cloth using dilute acids or enzymes .It is done to achieve even dyeing .

 

5.2. Scouring/cleaning– Fabrics are often soiled during manufacture and storage and has a lot of impurities like oils and waxes. Scouring is the removal of these impurities and is done with the help of detergents, alkaline solutions or enzymes. The absorbency, smoothness and neatness are enhanced after cleaning.

 

5.3. Bleaching –Bleaching produces white fabric by chemically removing any colour present in fabric.

Natural fibres are usually bleached with oxidative bleaches like hydrogen peroxide and sodium hypochlorite while synthetic fibres are bleached using reductive bleaches such as Sodium hydrosulphite.

 

5.4.Singeing – Protruding fibers on the surface of the fabric are burnt by passing the fabric rapidly over gas flames .Fabric becomes smooth.

 

5.5.Bio-polishing– The protruding fibers of cotton fabric are removed by the action of cellulase enzyme.

 

6. SPECIAL FINISHES

 

6.1.Mercerisation– Mercerization is one of the most important finishes for cotton. Cotton is a dull and rough fibre which wrinkles easily. It is, treated with cold concentrated sodium hydroxide solution under tension to make it stronger, lustrous and absorbent. As absorption is increased it improves dye affinity, producing brighter shades than unmercerized cotton. This is a durable finish.

 

6.2. Ammoniating

 

Rayon and cotton yarn or fabric are treated with a weak ammonium solution at 233°C and then quickly passed through hot water, stretched and dried in hot air. Swelling of fibre takes place. Luster and affinity for dyes is improved.

 

6.3.Tentering is done to dry and even out the fabric.The tenter frames consist of two endless chains which hold the fabric selvedge by series of pins or clips. The distance between the two chains is adjustable. The fabric after passing through this frame goes into the drying chamber where hot air removes any moisture present in the fabric and imparts dimensional stability.

 

6.4.Heat-setting– Internal tension is caused in synthetic fibres during manufacturing, heat-setting helps to eliminate this tension and fixes the fabrics in the stress-free state, avoiding shrinkage later on. It is also a process of decorating fabric by imparting wrinkles or pleats to the fabric and heat setting them into the fabric.

  6.5.Calendering – is a mechanical operation where fabric is pressed by passing it between two or more rotating rollers .The temperature and pressure of the rollers can be controlled and it produces a smooth flat fabric. If the calendar is heated it produces a lustrous surface. It reduces fabric thickness, yarn slippage and air permeability by closing the threads.

 

7. AESTHETIC FINISHES

 

7.1. LUSTER

 

7.1.1.Glazing–In this mechanical finish the fabric is treated with starches or resins before passing through hot calenders. The spaces between the yarns are filled up and a highly polished surface (glazed) is obtained.

 

7.1.2.Moire– Ribbed fabrics are doubled and passed between calenders in such a way that thick yarns of one side press and produce impressions on the other side. A watered effect is created due to difference in light reflection.

 

7.1.3.Cireing is done to silk, rayon or nylon. Wax or other compounds are applied to the fabric, followed by hot calendaring resulting in a super gloss appearance.

 

7.1.4.Schreinering– In schreiner calendar one of the metal rollers is embossed with fine diagonal lines. This produces smooth fabrics with soft luster.

 

 

7.1.5.Embossing– It is the process of producing (three-dimensional design) ie raised figures or designs on surface of fabric by passing between heated engraved metal roller and a soft calendar.

 

7.2.DRAPE

 

7.2.1. Starching / Stiffening– Fine quality or loosely woven fabric are treated in a mixture containing starch, waxes, oils and glycerine to add stiffness, weight and body. It also adds shine and smoothness to the fabric. It is a temporary finish.

 

7.2.2. Weighting– Silk fabric losses weight after degumming. To compensate the weight loss silk is treated with solution having metallic salts. It improves its feel and draping quality. Excessive weighting tends to weaken the fabric.

 

7.2.3. Parchmentization– In parchmentization, thin, transparent, light weight and crisp fabric called organdy is produced, by treating cotton with mild sulfuric acid which partially eats away the fabric.

 

7.2.4. Burnt out Finish- The fact that cellulosic fibres are harmed by acids is used to produce interesting designs. Controlled concentration of acids, temperature and treatment time is used on a blend of cellulosic and non cellulosic fibres to burn out some areas or make it transluscent.

 

7.3. TEXTURE AND HAND

 

7.3.1. Plisse–Plisse is a permanent finish, created by printing sodium hydroxide on cotton. The alkali shrinks the fabric in the treated areas and produces a puckered effect in the unprinted area.

 

7.3.2.Shearing

Shearing refers to the process of trimming off surface fibres or pile to control the length of the nap. It creates a smooth fabric with uniform surface. This process is done by a machine similar to a lawn mower.

 

7.3.3.Napping

 

Is a process, in which a hairy surface is achieved by passing the fabric under rollers having fine steel wires with small hooks on the ends .The hooks scrape the surface of the fabric pulling up the fiber ends. It produces a soft fabric with air trapped in the cells lending warmth to the fabric. It is commonly used in blankets, sleepwear and winter clothing.

 

7.3.4.Beetling

Beetling is a finish applied to linen or cotton. The fabric is pounded with heavy hammers. This process flattens the yarns of the fabric and produces a hard, flat surface with sheen.

 

7.3.5.Sueding/Peach Finish

When a fabric is passed through two or more emery-covered rollers, a soft nap is produced and the fabric gets a suedelike (velvet-like ) surface.

 

7.3.6.Gigging

 

Is the raising process is applied to wool fabrics. Teasels fixed to a cylinder brushes against a fabric gently and produces a short, soft nap.

 

7.3.7. Tigering

Tigering finish is done to a fabric already having naps to improve the height of the raised naps and to remove the loose fibers. The fibres not raised by napping process are pulled by the tiger roll, with long fine wires.

 

8. SPECIAL PURPOSE OR FUNCTIONAL FINISHES

 

8.1.Sanforization/Zero finish/Shrinkage control –Textile fibres are under constant tension during spinning, weaving and dyeing and they have a tendency of reverting back to their original state, this causes shrinkage in the fabric. The process of shrinking the gray good is carried out to avoid shrinkage. Sanforizing is a process where the fabric is first moistened with steam, run through a short tenter frame to straighten and smooth out wrinkles, through the compressive shrinkage head feed between a roller and rubber blanket, the rubber blanket compresses the weft threads and imparts (compressive shrinkage) and then through a drying unit to set the fabric. Labels such as ‘sanforised’ or ‘antishrink’ or ‘shrinkproof’ means the fabric has already undergone shrinkage control, and will not shrink on washing. This is a mechanical finish.

 

8.2. SHAPE RETENTION

 

Wash ‘n’ Wear – It is also called drip dry finish. Cotton fabrics or other cellulosics like rayon and linen wrinkle easily. When wash-n-wear finish is applied cellulosic fabrics acquire qualities similar to that of synthetic fibers. They become easy to maintain as they dry smooth, do not wrinkle and so needs no frequent ironing. This finish is a durable one. The fabric is saturated with resin and cured at temperatures of about 360°F. The fabric becomes stiff, less absorbent and more resistant to wrinkling. Tensile strength and abrasion resistance are reduced. This finish is also called Crease-Resistant finish or “wrinkle-free”finish.

 

8.3.APPEARANCE RETENTION

 

8.3.1.Stain and Soil Resistant Finishes avoid soil and stains from being attracted to fabrics and helps to maintain a clean look of a product like carpets and upholstery. Chemicals such as fluorocarbons and organo silicone compounds are used to coat the fabric surface. Thus, a protective coating is formed which inhibits penetration of stains and soil. Another approach is to increase the surface tension so that the liquid based stains roll off in a manner similar to droplets on lotus leaves.

 

8.3.2. Non-slip finishes– Some fabrics with synthetic warp and weft threads in loosely-woven fabrics have the tendency to slip because of their surface smoothness and appearance is no longer attractive. Non-slip finishes is applied to a yarn to make it resistant to slipping and sliding when in contact with another yarn. The fabrics are treated with resins, stretched and dried under tension.

 

8.3.3. Anti-pilling finish– Pills are balls of tangled fibres that appear on fabric surfaces. Fabrics with pills have an unsightly appearance. Pills are common with spun yarn fabrics, and knits especially when they contain synthetics. Loose fibres are pulled from yarns and are formed into spherical balls by abrasion. Anti pilling finish reduces the forming of pills on fabric and is based on the use of chemical treatments which aim to suppress the ability of fibres to loosen and also to reduce the mechanical resistance of synthetic fibre.

 

8.4. COMFORT RELATED FINISH

 

8.4.1. Water-RepellentFinishes

 

Water-repellent finishes resist absorption and penetration of water for a given period of time depending on time and force of the water. After sometime, water may pass through even a water repellent fabric. As opposed to waterproof fabrics, these fabrics are porous, permitting the body to breathe and therefore are more comfortable. This finish  applied to fabrics found in raincoats, hats, caps, umbrellas and shower curtains. Water repellent fabrics may be nondurable, semi durable and durable finishes.

 

8.4.2.Hydrophilic finishes– Synthetic fibres have low moisture absorption and this makes it uncomfortable when it is in contact with the skin. Hydrophillic finish imparts absorbency using chemicals such as ammonium compounds, humectants and wetting agents .Such finished fabrics readily absorb perspiration, reduce static cling and increase fibres moisture holding power. This finish is useful for towels, sports wear and other items where moisture absorption is important.

 

 

8.4.3. UV Protection –Fabric treated with UV absorbers deflect the harmful ultraviolet rays of the sun, reducing a person’s UVR exposure and protects the skin from damage. This protection isexpressed as SPF (Sun Protection Factor), higher the SPF value, better is the protection against UV radiation.

 

8.4.4. Softening Finish– is required for pleasant hand and better drapability. Fabrics are harsher and stiffer because of their construction or due to some prior finishing process. Softening can be done by either mechanical or chemical process. Simple calendering softens hand, but it is temporary. Silicone compounds are used mostly as softner.

 

8.4.5. Anti-static finish – Static electricity causes problems of clinging to the wearer and attraction of dirt. Anti-static finishes are chemical substances applied to synthetic textile for the purpose of reducing or eliminating static electricity which accumulates on these fibres. These chemicals absorb small amounts of moisture from the atmosphere, thus reducing the dryness of the fabric and making it comfortable to wear. Anti-static finishes are semi-durable. It also prevents dust from clinging to the fabric.

 

8.5. BIOLOGICAL CONTROL

 

8.5.1. Anti-microbial finish- The inherent properties of textiles fibres like humidity and warmth encourages the growth of the micro organisms. Anti microbial finish is a treatment which makes the fabric resistant to bacterial growth, odor causing germs and prevent the cloth from damage.

 

Anti-microbial agents can be applied to textile by exhaust, spray, pad-dry-cure, coating or foam techniques. Chemicals used are quarternary ammonium compounds, melamine resins with zinc nitrate. This finish is extensively used in healthcare sector like surgical gowns, nurse’s uniforms, infant wear, sports and leisure clothes.

 

8.5.2. Mothproofing Finishes

 

Protects protein-containing fibres, such as wool and silk, from being attacked by moths, beetles and other insects. It is achieved by using substances containing fluorine such as sodium fluoride, aluminium fluoride, potassium fluoride and sodium antimony fluoride.

 

8.5.3. Anti Mildew

 

In suitable conditions of humidity and heat, cellulose can be permanently damaged by mildew. This can be prevented by using antiseptics, bacteria controlling products containing quaternary ammonium salts, and phenol derivatives.

 

8.6. SAFETY RELATED

 

Fire Resistant or Flame Retardant finish Fabrics cannot be made absolutely fire proof but can be treated to retard flammability. It imparts safety to the individual using them. They do not propagate the flame and are self extinguishing. Flame retardants are chemicals containing phosphorous or chlorinated hydrocarbons which are applied to fabrics to inhibit or suppress the combustion process. It is commonly used for children’s garment, fire fighter uniform, carpets and furnishing.

 

8.7. OTHER FINISHES

 

8.7.1. Fragrance Finish – Microencapsulation is a useful method for applying various functional finishes on textiles. Aroma encapsulated capsules are used for fragrance finish. The fragrance from the capsule is released during the application of pressure onto the fabric. A binder is used to fix the capsules as it has no affinity to fabrics.

 

8.7.2. Waterproof Finishes –Water proof fabrics are coated with natural or synthetic rubber that is insoluble in water. It allows no water to penetrate, but is uncomfortable as it traps moisture next to the body. It is a durable finish.

 

8.7.3. Plasma finish- In plasma treatment the surface of the fabric exposed to the action of the plasma is modified physically and chemically. Mechanical properties are not altered. A gas (oxygen, nitrogen, air, argon etc ) injected inside a reactor at a specified pressure, is ionized by the presence of two electrodes in the presence of an electric field. The fabric, sliding through the electrodes, is bombarded by the elements of the plasma causing surface modification.

 

9. FINISHES FOR WOOL

 

9.1.Decatising is a finish done to bring dimension stability, enhance lustre and improve the appearance and feel of woolen fabrics. In this process the fabric is wound on a perforated roller and is immersed in hot water or has steam blown through it

 

9.2.Carbonising– is burning of vegetable matter in wool using dilute sulphuric acid to achieve uniform dyeing

 

 

10. FINISHES ON DENIM:

 

10.1. Stone wash– In stone washing process, freshly dyed denims are spun together in large washing machines with pumice stones. The pumice stone abrades the surface of the denim, removing some dye particles from the surfaces of the yarn producing a faded or worn out look.

 

10.2. Enzyme Washing

 

Cellulase enzyme can be used to produce stone washed effects on denim fabrics. The surface colour of the denim is removed by cellulase. This process gives a soft feel to the fabric and does not damage the cloth as stone washing.

 

 

10.3. Sand Blasting

 

Sand blasting is a mechanical process. Worn out or abraded look is achieved on specific areas of the garment using the technique of blasting abrasive materials in granular or powdered form at very high speed and pressure through a nozzle.

 

10.4. Whiskering –Laser is used to create crease lines on denim

 

  1. Summary

Finishing is a final step in textile processing and it improves the appearance, feel or imparts required qualities to the fabric. Finishes may be applied using chemical or machinery and it may be temporary, semi permanent or permanent .It may be a basic finish done for all fabrics or special finishes applied based on the end use of the fabric.

 

you can view video on Textile Finishes

Web links

  • https://en.wikipedia.org/wiki/Finishing(textiles)
  • Textilelearner.blogspot.co.uk/2011/03/description-of-textile-finishing-1796.html