FABRIC DESIGN / DECORATION / QUESTIONS & ANSWERS

  

Question 1                                                                                                (30 marks)

a. The colouring of fabrics in textile establishments is done through printing, staining (painting) or by dyeing. As a textile designer, discuss in detail, how you can use batiking or tie-dyeing to design a 3-yard mercerized cotton fabric with vat dye.

b. Differentiate between table dyeing and dyeing by immersion.

 

Question 2                                                                                               (30 marks)

There are varied types of dyeing machines used for the colouring of fabrics in large-scale textile firms. Write on the following dyeing machines and discuss the advantages and disadvantages of each of them.

a.     Pad dyeing machine

b.     Winch machine

c.      Beam dyeing machine

d.     Jet dyeing machine

 

Question 3                                                                                               (30 marks)

Printing of fabrics can be done with quite several techniques by textile experts. Clearly discuss how prints are made on fabrics with the following techniques:

a. Sublistatic printing

b. Screen printing

c. Block printing

d. Duplex printing

 

ANSWERS

QUESTION TWO

THE FOLLOWING DYEING MACHINES

                        a) Pad Dyeing machine

 It is a continuous process used in producing of piece- dyed goods that can withstand tension and pressure. Fabrics pass through a dyebath pads or rollers that squeeze out the dye and then into a steam or heated chamber in which the dye fixed or set.

Advantages of Pad Dyeing Machine

➢ Uniform liquor application over the whole fabric width.

➢ Different liquor application in the range of side-center-side zone is possible.

➢ Attractive price.

➢ Easily operation.

➢ Reliable and economical padder.

 

                        b) Winch Dyeing Machine

 It is frequently used in batch dyeing of wool and knitted products as place relatively little tension on the fabric during dyeing. Fabric is formed into endless, circular chain and is rotated through the dye.

Advantages Winch Dyeing Machine

❖ Simple construction and therefore economical to purchase and operate. Suitable for all type of fabric especially lightweight.

❖ It imposes much less tension than jigger so it’s suitable for dedicate fabrics.

❖ Scouring efficiency is high due to greeter mechanical action cause by constant reformation of lengthways fold.

❖ Tubular knitted fabrics are scoured and dyed extensive because of the low tension.

❖ Crimps are developed due to greater mechanical action and low tension.

❖ The dyed fabric is thicker with fuller handle, more fabric covers and better crease recovery.

 

Disadvantages of Winch Dyeing Machine

❖ The temperature varies in different parts. The heating unit is so present only in one compartment so when the fabric leaves that compartment it cools and then re-enter. So, for temperature sensitive dyes it’s a major drawback.

❖ Excessive movement may lead to undesirable felting in wool fabric.

❖ The fabric is irregularly piled and uneven dyeing may occur unless suitable dyes levelling agent are used.

 

 

❖ Due to high liquor ratio, dye exhaustion is poor and considerable amount of dye remains in the bath which hampers the economy.

❖ Formation of running creases during dyeing may not be removable even after stuttering.

❖ Elongation and deformation may occur due to longitudinal tension.

❖ Longer rope may cause entanglement at the bottom.

 

C. Beam Dyeing Machine

It is used for light weight fairly open weave fabrics and utilizes the same principles as the beam dyeing of yarns. A fabric is wrapped around a beam and immersed in a

dyebath.

Advantages of Beam Dyeing machine

❖ The fabric is put under controlled tension, and is wound on to a perforated beam. This results in elimination of crease from the fabric.

❖ It also ensures total control of dimensions of the roll of fabric.

❖ The fabric is not allowed to do any movement during the process of dyeing.

 

Disadvantages of Beam Dyeing Machine

❖ Fabric of different width cannot be dyed together on a single beam.

❖ The dyed fabric may be display moiré effect if it is tightly due to shrinkage.

❖ Uneven dyeing may occur if the beam is fully loaded as the dye liquor has penetrate several layers of fabric.

 

d. Jet Dyeing Machine

It is a relatively new method of dyeing that utilizes jet production to improve dye penetration. Dyeing takes place in a closed system that carries a fast-moving stream of pressurized dye liquor (dye solution). Jet dyeing has the advantage of being economical in operation and at the same time allowing a high degree of quality control.

Advantages of Jet Dyeing Machine

•                     • Lower material to liquor ratio provides savings in energy & faster heating and cooling.

•                     • Less lengthways tension & slightly fullness of handle.

•                     • Vigorous circulation of liquor & material causes quicker dyeing.

•                     • Frequent movement of fabric minimizes creasing problem.

•                     • High fabric transport speed by adjusting nozzle valve to cause level dyeing.

•                     • Less dye at the surface resulting in quicker washing with marginally better fastness properties.

 

Disadvantages of Jet Dyeing Machine

•                     • Typical crease marks which might be developed during high temperature dyeing making it difficult to remove in finishing.

•                     • High capital investment & maintenance costs.

•                     • Limited accessibility to the material when the machine is running, the fabric is loaded & unloaded through a small port.

•                     • Internal cleaning is difficult as the machine is completely enclosed. In particular, Polyester Oligomer deposits may develop on the hot surfaces & later dislodge. (Cleaning is done by circulating Caustic Soda or Sodium Dithionite).

•                     • Any roughness inside the machine causing snagging of the fabric is difficult to locate.

•                     • Vigorous movement of the liquor may create severe foaming.

•                     • The force of the jet may damage delicate fabrics.

•                     • Sampling of the dyed fabric during dyeing is difficult.

•                     • Fabrics from spun yarns of staple fibres may tend to become quite hairy in appearance because of abrasion.

 

QUESTION 3. How prints are made with the following techniques

a. Sublistatic Printing

Heat transfer or sublattice printing is a method of printing in which special dyes are first printed

onto a paper before the designs are transferred from the paper to the fabric. The transfer of

colours take place as the colour sublimes through vaporisation. This is achieved by rolling

pressure and at a high temperature (424°F) or (200°C). This printing method is used on

synthetic fabrics with the use of mostly disperse dyestuffs.

b. Screen Printing

Screen printing is basically a stencil printing technique. It is a developed version of the

stencil process. A screen refers to wooden, plastic or metal frame with a mesh fabric (man–

made or natural) like silk mesh or organdy stretched taut over it. Portions of the mesh have

the holes blocked off with P.V.A. material (non–printing area) and the printing paste is forced

through the open printing areas by a rubber or metal blade called ‘squeegee’ to effect print on

the fabric beneath it. Flat-bed screen printing and rotary screen-printing styles are examples of this method of fabric printing.

ANOTHER ANSWER 

problem

• High fabric transport speed by adjusting nozzle valve to cause level dyeing.

• Less dye at the surface resulting in quicker washing with marginally better fastness properties.

Disadvantages of Jet Dyeing Machine

• Typical crease marks which might be developed during high temperature dyeing making it difficult to remove in finishing.

• High capital investment & maintenance costs.

• Limited accessibility to the material when the machine is running, the fabric is loaded & unloaded through a small port.

• Vigorous movement of the liquor may create severe foaming.

• Fabrics from spun yarns of staple fibers may tend to become quite hairy in appearance because of abrasion.

c. Beam Dyeing Machine

It is used for light weight fairly open weave fabrics and utilizes the same principles as the beam dyeing of yarns. A fabric is wrapped around a beam and immersed in a dyebath

Advantages of a Beam Dyeing Machine The fabric is put under controlled tension, and is wound on to a perforated beam. This results in elimination of creases from the fabric. It also ensures total control of dimensions of the roll of fabric. The fabric is not allowed to do any movement during the process of dyeing.

1. The fabric is put under controlled tension, and is wound on to a perforated beam. This results in elimination of creases from the fabric. It also ensures total control of dimensions of the roll of fabric.

2. The fabric is not allowed to do any movement during the process of dyeing. This actually means that there is no application of mechanical action on to the fabric. As shown in the figure, there is no movement of the fabric as the hydrostatic pressure of the pump forces the dye liquor through the fabric roll.

Disadvantages

1. There is possibility of entanglement of light- weight fabric during dyeing.

2. Lose fibres removed from the fabric may get redeposited on the fabric surface as well as on the interior of the jet dyeing vessel, this problem these not arise in beam dyeing.

a. Pad Dyeing Machine

It is a continuous process used in producing large quantities of piece-dyed goods that can withstand tension and pressure. Fabrics pass through a dyebath then through pads or rollers that squeeze out the excess dye and then into a steam or heated chamber in which the dye is fixed or set.

Advantages of pad-batch dyeing

The pad-batch dyeing system has the following advantages over conventional batch systems such as jets, becks, etc.: 1. Simplicity of dyestuff application. 2. Reduction in water consumption by 50 to 80%. 3. Reduction in energy consumption by up to 60%. 4. Reduction in chemical costs, other than dyestuff, by up to 50%, due to elimination of salt and reduction of alkali requirements. 5. Reduction in labor costs by 40 to 60%. 6. Minimum fabric abrasion. 7. Excellent shade reproducibility from lot to lot.

Disadvantages of pad dyeing machine

Difficult to make amendments to of shade batches so pressure to get things right first time, posset not viable on less high-quality machinery is used, require off line bleaching and wash of which makes planning more complex.

b. Winch Dyeing Machine

It is frequently used in batch dyeing of wool fabrics and knitted products as it places relatively little tension on the fabric during dyeing. Fabric is formed into an endless, circular chain and is rotated through the dye.

Advantages of Winch Dyeing Machine

• Simple construction & therefore economical to purchase and operate.

• Suitable for all types of fabric specially lightweights.

• It imposes much less tension than Jigger so it’s suitable for delicate fabrics.

• Scouring efficiency is high due to greater mechanical action caused by constant reformation of lengthways folds.

• Tubular knitted fabrics are scoured & dyed extensive because of the low tension.

• Crimps are developed due to greater mechanical action & low tension.

• The dyed fabric is thicker with fuller handle, more fabric cover & better crease recovery.

Disadvantages of Winch Dyeing Machine

• The temperature varies in different parts. The heating unit is present only in one compartment so when the fabric leaves that compartment it cools & then re-enters. So, for temperature sensitive dyes it’s a major drawback.

• Excessive movement may lead to undesirable felting in wool fabrics.

• The fabric is irregularly piled & uneven dyeing may occur unless suitable dyes & levelling agents are used.

• Due to high liquor ratio, dye exhaustion is poor & considerable amount of dye remains in the bath which hampers the economy.

• Formation of running creases during dyeing may not be removable even after stentering.

• Elongation & deformation may occur due to longitudinal tension.

• Longer rope may cause entanglement at the bottom.

Question Three (3)

a. Sublistatic printing;

Heat transfer or sublistatic printing is a method of printing in which special dyes are first printed onto a paper before the designs are transferred from the paper to the fabric. The transfer of colours takes place as the colour sublimes through vapourisation. This is achieved by rolling pressure and at a high temperature (424°F) or (200°C). This printing method is used on synthetic fabrics with the use of mostly disperse dyestuffs.

Another type of unit for printing individual pieces, cloth, sweaters, hosiery, drapery panels

A process involving the transference of a printed design from paper to cloth. Applying heat to both fabric and paper, the dyes on the transfer paper sublime to condense in the fiber of the fabric surface. Form this the printer is invited to select a suitable design.

b. Screen printing

Roller printing is the machine method of printing designs on cloth by engraved rollers. It turns out colour –designed fabrics in vast quantities at the rate of thousands of yards an hour. Roller printing is also referred to as Intaglio or Machine printing. The printing areas are recessed below a smooth surface. The engraving of patterns unto the copper rollers in itself is a highly technical and lengthy process. The technique of roller printing is especially used for very large

batches but face great completion from rotary screen printing in recent times. It has also resulted in the less use of the block printing technique. Block printing is comparatively considered to be time consuming and too expensive to use.

The technique of creating a picture or pattern by forcing ink or metal on to a surface through a screen of fine material, screen printing allows large blotches of colour, skill in lining up design is garter in roller printing, Side of pattern limiter only by side of screen exclusive design may be produce. Capital layout for mechanical printed is high.

c. Block printing;

Block printing is the simplest of the printing techniques and requires only a limited technology. It is basically hand printing method and the oldest method of printing designs on fabrics. It is not preferred for printing fabrics on commercial quantities by most experts as compared to techniques like roller printing due to its slow rate of production.

Some experts assign 2000B.C. as the date for the discovery of block printing for fabric decoration at Caucasus in Russia. Blocks that were used in printing textiles have been recovered from Egyptian graves of the 4th century A.D.

In block printing, the print paste is applied to the textile material from a raised surface on a wooden base or block. It is thus a relief method. In the early and mid-18th century, simple wood block was used for line work and small shapes. The design is transferred onto the block and the background and non-printing areas cut to a depth of 1-2cm according the type of shape and type of fabric to be printed.

Fine clothes need less deep cutting. Areas over 5cm in width do not print well because the wood does not hold the water-based dyes easily enough to give a regular result. When bigger areas are to be printed, a colour block is used.

Thick felt is pressed into the center of the motif so that it is level with the wooden outline. The wood outside the shape is then carved away leaving a firm area of pattern in felt with a supporting wall of wood. The felt holds the dye readily and allows the block to give out its colour evenly to the fabric.

To make hand–blocked prints, the following steps are used:

i. Carve the design onto a wooden or metal block.

ii. Apply dyestuff in paste form to the design on the face of the block.

iii. Press down the block firmly by hand on selected portions of the fabric to print the design.

iv. Repeat the printing at other predetermined areas on a particular length of fabric, if desired by the designer.

v. Use additional carved blocks to print the second, third, or any additional colour if needed for the design. Each colour in the design requires a separate block for the printing. The more the colours used, the more expensive the hand–blocked print will be, because of the enhanced beauty of the design as well as the labour involved in the hand printing.

This simple printing technique consist of using wooden block, one side of which is carved with a pattern or design which is raised, the raised pattern could be smeared with coloring matter pressed on to the fabric there by transferring the design

d. Duplex printing

Duplex printing is done on a special machine that prints designs on both sides of the fabric at the same time. The fabrics may be passed through the roller printing machine in two separate operations or through a duplex printing machine in a single operation. Duplex printing produces an equally clear outline on both sides of the fabric. The design is applied so skillfully by careful registration of the printing cylinders that may be mistaken for a woven design. This process is seldom used now, for it is expensive to create duplex prints.

simulates a woven pattern by printing the fabric on both sides. Most duplex prints are produced on direct roller print equipment, some are produced on rotary screen printers. Most often they are made to imitate more costly woven yarn dyed design effects such as stripes, checks, and plaids.

ANOTHER ANSWER.

 

  QUESTION 3

a.       Duplex printing: Is a method of printing the design on both side of the fabric to give the design clear colour, duplex printing simulates a given pattern by printing the fabric on both sides most duplex print are produced on direct roller printer equipment, some are produced on rotary screen printer most often they are made to imitate more costly woven. Yarn dyed design effects such stripes, check, and plaids.

 b. Screen printing: In screen printing the design is transferred onto a well stretched screen so that all but the design is covered by a resist material. The design which is now open for dye penetration is put onto the cloth and the dye forced through the tiny holes by a squeegees

      c.  SUBLISTATIC PRINTING: It is a method of printing in which special dyes are first   printed onto a paper before the designs are transfer of colours takes place as the fabric, the transfer of colours takes place as the colour sublimes through vapourisation

     d. Block printing: This is the oldest method for printing fabrics and it is done with wooden blocks by hand. A wooden block on which has been carved the design to be printed is dipped in a print past and stamped on the cloth. The stamped cloth is dried and then given finishing treatment.

 

Question 2

BEAM DYEING MACHINE: It is used for light weight fairly open weave fabrics and utilizes that same principles as the beam dying of yarns. A fabric is wrapped around a beam and immersed in a dyebath.

ADVANTAGES OF BEAM DYEING MACHINE

·         The fabric is not allowed to do any movement during the process of dyeing

·         The fabric is put under controlled tension and is would on to a perforated beam this results in elimination of creases from the fabric.

           DISADVANTAGES OF BEAM DYEING MACHINE

·         Fabric of different width can be dyed together on a single beam

·         The dyed fabric may be display more effect if it is tighten due to shrinkage

·         Uneven dyeing may occur if the beam is fully  loaded as the dye liquor has several layers of fabric

 

1.      PAD DYEING MACHING

Pad dyeing is a process of dyeing in which the fabric in open width is padded with dyestuff and in then steamed. It’s an ideal machine for reactive dying. Light, pale and medium shades can be dyed in this machine. Continuous roller steamer is used for diffusion of reactive, vat, sulphur and direct dyes into cellulosic fibers in an atmosphere of heat and moisture that is created by saturated steam injected into the steamer

 

 

ADVANTAGES OF PAD DYEING MACHINE

·         wash off can easily be done

·         can be used to serve different wet process operations

·         it exerts lot of tension

·         done on a continues process

·         need less time

   DISADVANTAGES OF PAD DYEING MACHINE

·         batch to batch shade variation occurs

·         uneven dyeing occurs

·         need high man power

·         batching is complicated

·         need high liquor ratio

WINCH MACHINE: it is the oldest method but good for light fabrics which cannot withstand the tension of the methods described above and for heavy good like woollens. It is also referred to as real of beck dyeing.

ADVANTAGES OF WINCH DYEING MACHINE

·         This type of dyeing is suitable for all types of fabric specially lightweights.

·         It imposes much less tension than digger so it suitable for delicate fabrics

·         The dyed fabric is thicker with fuller handle more fabric cover and better creases recovery.

·         Simple construction is economical purchased and operate.

·         Crimps are developed due to greater mechanical action and low tension

 

DISADVANTAGES OF WINCH DYEING MACHINE

·         Longer rope may cause entanglement at the Elongation and deformation may occur due to longitudinal tension.

·         Excessive movement may lead to undesirable felting in wool fabric.

·         Formation of running creases during dyeing may not be removable even after stentering.

·         Due high liquor, dye remains in the bath which hampers the economy.

JET DYEING MACHINE: It is a relatively new method of dyeing that utilizes jet   production to improve dye penetration, dyeing takes place in a closed system that carries a fast moving stream of pressurized dye liquor or dye solution.

     ADVANTAGES OF JET DYEING MACHINE

·         Less lengthways tension or slightly fullness of landle.

·         High fabric transport speed by adjusting nozzle valve to cause level dyeing

·         Frequent movement of fabric minimizes creasing problem

·         Less dye at the surface resulting in quicker washing with marginally letter fastness

·         Lower material to liquor ratio provides savings in energy or faster heating and cooling

DISADVANTAGES OF JET DYEING MACHINE

·         The force of the jet may damage delicate fabrics

·         Sampling of the dyed fabrics during dying is difficult to be become quite hairy in appearance because of abrasion

·         High capital investment and maintenance costs vigorous movement of the liquor may create severe foaming