Complete Lab

LAB EXPERIMENT 01 Name: _____________________________________________ _______________________

ID No.

Remarks:________________ Signature of the lab tutor_______________ Date:_________________

Introduction to Textile Printing PERFORMANCE/OBJECTIVES 

To be well familiar for Textile printing.

THEORY "It is the process by which localized dyeing are produced." It can also be defined as: "Localized colouration of the textile substrate." PRINTING SCENARIO: These are the three major criteria's that must be considered for the efficient production in printing process.   

Printing Techniques. Substrate (Fiber) Type. Dye Stuff Classes (Colorants)

1. PRINTING TECHNIQUES: There are five types of printing techniques that are used in the modern textile industry.

S.No

Techniques

Contibution In Printing Industry (%)

i.

Rotary Screen Printing

61

ii.

Flat Screen Printing

23

iii.

Cylinder Printing

10

iv.

Transfer (Paper) Printing

4

v.

Others (Block) Printing

2

1

2. FIBER TYPES:

S.No

Fibres

Contribution In Processing (%)

i.

Cotton

48

ii.

Polyester/Cotton (Blends)

19

iii.

Viscose

15

iv.

Polyester

13

v.

Others(acrylics,wool,silk,nylon,e tc)

5

3. DYE STUFF CLASSES (COLORANTS):

S.No

Dye Stuffs

Contribution (%)

i.

Pigments

46

ii.

Reactive

27

iii.

Disperse

15

iv.

Vat

7

v.

Others

5

In

Processing

Test Results:

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Review Question:

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LAB EXPERIMENT 02 Name: _____________________________________________ _______________________

ID No.

Remarks:________________ Signature of the lab tutor_______________ Date:_________________

Preparation of fabric & paste for printing

PERFORMANCE/OBJECTIVES 

To be well familiar for fabric preparation and paste.

THEORY Textile printing is used to signify the production, by various means of colored patterns on designs upon all sorts of textile fiber. Textile printing is the most important and versatile of the techniques used to add design, color, and specialty to textile fabrics.

Steps of Printing The basic steps in the printing process are as follows: 1. Preparation of the fabric 2. Preparation of the print paste. 3. Printing the fabric. 4. Drying the printed fabric. 5. Fixation of the printed dye or pigment. 6. Afterwashing.

There are many factors encountered for fabric preparation prior to printing, mainly depents on two factors: 1. Type of fabric to be printed 2. Type of colorant to be applied. Preparation of cloths: 4

Following process are carried out on fabric for printing: 1. Singeing 2. Desizing 3. Scouring 4. Bleaching 5. Mercerization 6. Heat setting

Color preparation: Print paste is a viscous solution of printing ingredients referred below that is used for textile printing. The main three printing ingredients are: 1. Dyestuff or pigments 2. Thickeners: 3. Chemicals and waters:

Dyestuff or pigments For printing color is prepared in paste form. There are two types of paste used:  

Pigment paste Reactive paste

PIGMENTS

DYES

Good light stability

Relatively low light stability

No Diffusion between layers

Prone to diffusion in layers

Poor ink stability

Produce stable inks

Low color Brilliance

High color brilliance

Inks Difficult to formulate

Easy ink formulation

No wide range of colors

Wide range of colors

Less rubbing fastness

Good rubbing fastness

Recipe:  1000 kg of pigment paste:  Urea  Liquor ammonia  Thickener  Binder

4% 1.4 % 4 % (further depends on design and screen) 3% 5

 1000 kg of reactive paste:  Urea  Soda bicarbonate  Resist salt / RG  Thickener

15 % 4% 1.5 % 4 % (further depends on design and screen)

Note: IPS machine is used for color paste preparation. In Popular Fabric Mills, this machine is out of order now days.

Thickeners: Thickener can be defined as a substance used to increase the viscosity of a print paste or other fluid, in order to control its flow properties.

Chemicals and waters: The main types of chemicals used for textile printing are wetting agents, solvents, solution acids, dispersing agents, hygroscopic agents, oxidizing & reducing agents, defoamers, acids, alkalis, catalyst & carriers, swelling agents etc.

Test Results: __________________________________________________________________________________ __________________________________________________________________________________ ___________________________________________________________________________ 6

Review Question:

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LAB EXPERIMENT 03 Name: _____________________________________________ _______________________

ID No.

Remarks:________________ Signature of the lab tutor_______________ Date:_________________

Printing Paste Requirement and Preparation of Thickener OBJECTIVES  Identify the requirements of printing paste. THEORY UREA: It is used as a hygroscopic agent or humectants:  

Keeps the paste in wet form. Avoid blocking/chocking of screens in screen-printing.

THICKENING AGENTS/THICKENERS ARE USED:    

To provide viscosity of print paste up to 1000-4000 centipoises (cp) for reactives and 8000 cp for pigments. Responsible for localized dyeing, must be non-reactive and removed from the surface after their application, because their presence onto the substrate can change the texture of fabric. Viscosity has a great importance in print paste, if viscosity of paste reduces or paste spreads in the design after printing, this is will be considered as a fault. Mostly Starches, gums and Sodium Alginate used as thickners

SELECTION OF THICKENERS:    

Economical Compatible with the recommended pH for a particular process. Non-reactive Easy removal

BINDERS: Binders plays key role in pigment printing. Binder is monomers which on heating get converted into polymers.

8

Binder actually hold the pigment color and sandwich it between fabric surface and plastic coating and this coating help color to stick there and stand with high and severe conditions.

WETTING AGENTS: A chemical that can be added to a liquid to reduce its surface tension and make it more effective in spreading over and penetrating surfaces SOLVENTS: Solvents are liquids or gases that can dissolve or extract other substances. DISPERSING AGENTS: Dispersing agents are surface-active ingredients, which ease the incorporation of pigments and fillers into a liquid. Bunch up are broken up by shearing whereby new surfaces are created. They are wetted by dispersing agents which stabilize the aggregates of pigments or dyes. DEFOAMERS: A defoamer or an anti-foaming agent is a chemical additive that reduces and hinders the formation of foam in industrial process liquids. The terms anti-foam agent and defoamer are often used interchangeably. LIQUOR AMMONIA: It is used: To maintain pH towards the alkaline medium, generally up to 10 FIXATION: It is achieved by using Sodium Bicarbonate in Reactive Dyestuff. BLANK PASTE: The paste containing all the solutes in water, except colourant (dyestuff) is known as blank paste.

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Test Results: __________________________________________________________________________________ __________________________________________________________________________________ ___________________________________________________________________________

Review Question:

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LAB EXPERIMENT 04 Name: _____________________________________________ _______________________

ID No.

Remarks:________________ Signature of the lab tutor_______________ Date:_________________

Printing Styles OBJECTIVES  To determine the different methods / styles of textile printing.

THEORY There are three printing styles that are mostly used in the textile industry. DIRECT STYLE: Dye in a thickened formulation is applied to selected areas of the fabric producing a coloured pattern. Fabric must be pretreated (bleached) and dyed. DISCHARGE STYLE (DUPLEX PRINTING): Background colour is decolourized due to the discharging chemical from the localized area. Reactives and pigments are used for this purpose. Fabric is first dyed and printed so that the dye present in the printed areas is destroyed. There are two possibilities in discharge style of printing: 1. If the original white of the fabric reappears, the process is called as a white discharge. 2. Coloured discharge could be produced, if the pre-dyed ground is destroyed while at the same time another dyestuff is left in its surface. *Sodium Sulfite is the main product for discharge and resist styles. SEQUENCE OF OPERATIONS: 

Dyeing: Conducted by continuous method (pad and dry), but the dye is not 11



fixed. Ground dyeing is always carried out by reactive dyes. Pick up must be 70% and controlled drying is carried out at maximum 80°C. Printing: By using direct style and then dyes are fixed.



Soaping: In continuous form.

SPECIAL SELECTION OF DYESTUFF FOR DISCHARGE STYLE OF PRINTING: Special dyes are selected for ground dyeing, which are not compatible with discharging chemical (sodium sulfite) used in the print paste for discharging. When this paste is applied on the pre-dyed fabric, it becomes decolourized. For coloured discharging, dyes must be selected which have compatibility with discharging chemical. TYPES OF REDUCING AGENTS THAT CAN BE USED AS DISCHARGING CHEMICAL: 

Strong Reducing Agent: Sodium Hydrosulfite (Hydro) or Sodium Dithionite



Moderate Reducing Agent: Sodium discharging) Mild Reducing Agent: Sodium Sulfide



Sulfite

(Mostly

recommended

for

RESIST STYLE: 1. Pretreated fabric (pre-wash) 2. Printing 3. Dyeing

Dye is applied to a fabric but not fixed. A resist formulation is printed on selected areas of the fabric. The resist agent prevents the fixation of the dye in subsequent processing. The unfixed dye is washed away leaving a white pattern. If the resist agent is applied before the dye, the method is called a "preprint process." If the dye is applied first followed by the resist formulation, the method is called an "overprint process."

Test Results:

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Review Question:

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LAB EXPERIMENT 05 Name: _____________________________________________ _______________________

ID No.

Remarks:________________ Signature of the lab tutor_______________ Date:_________________

Screen Printing Technique OBJECTIVES  Demonstration of screen printing technique. MACHINES  

Screen Sampling machine

THEORY SCREEN PRINTING TECHNIQUE: It is the technique in which screens are used along with the print paste to print the design onto the fabric. SCREEN: It is a perforated sheet having some holes partly opened and some holes partly closed. Screens possess a particular mesh number: Mesh number = Number of holes/sq. inch This number varies depending upon the types of dye and substrate. Pigment Printing = 40—60 mesh no. Reactive Printing = 80—120 mesh no. Disperse (Polyester) Printing = 120—150 mesh no. On the basis of screen shapes, screen-printing is divided into two main types:  FLAT SCREEN PRINTING: 14

Having horizontal angle of 180° and made up of Nylon.  ROTARY SCREEN PRINTING: It is the printing in which circular/cylindrical shaped screens are used having 360°angle and made up of metals i.e. Nickel or Cobalt. This technique is gives more production than flat screen printing, rotary printing machine can be run up to 20—80 m/min. Its biggest advantage is high production and variety of designs and the limitation is, it is not suitable for short batches.

 DIFFERENCES BETWEEN FLAT AND ROTARY SCREEN PRINTING

Parameter

Rotary Screen

Flat Screen

SEQUENCE OF OPERATIONS IN SCREEN-PRINTING USING REACTIVE DYESTUFFS: 1. 2. 3. 4.

Print Dry Fixation Washing/Soaping

• •

Vinyl Sulfone type reactive dyes (Low Reactivity) are used for printing purpose. Drimarene-P (reactive) dyes are produced by CLARIANT for printing.

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Test Results: __________________________________________________________________________________ __________________________________________________________________________________ ___________________________________________________________________________

Review Question:

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LAB EXPERIMENT 06 Name: _____________________________________________ _______________________

ID No.

Remarks:________________ Signature of the lab tutor_______________ Date:_________________

Block printing of cotton fabric

OBJECTIVES  Process of block printing MACHINES 

Wooden blocks

THEORY Woodblock printing is a technique for printing text, images or patterns used widely throughout East Asia and probably originating in China in antiquity as a method of printing on textiles and later paper. It is the oldest and simplest way of printing. In this method a wooden block with a raised pattern on the surface was dipped into the printing colorant and then pressed face down on to fabric. The desired pattern was obtained by repeating the process using different colors. Generally the wooden block is carved out of hand. Printing is done manually in this method. PROCESS

17

1. The first step is to sketch the design. It is important to reverse the image if you are using text, as the printed image will be the reverse of what is on the block. Once you have the image ready, and then transfer the design on to the linoleum to give an outline of where to carve. 2. The next step is to carve the design. Carve away the parts that you don’t want to print, as the ink will be applied to the raised surfaces to print the design. Whatever surface is untouched will be what prints onto the paper. Carving a block can take anywhere from an hour for a small piece, to several weeks or even months depending on the size and detail of the image. 3. Use a range of knives, with very small-tipped knives for carving outlines and details, and much larger ones for cutting away the background. Carving the blocks takes a lot of patience, because if your hand slips it can damage the whole piece. With practice, you can learn the amount of pressure it takes to carve the material. 4. Once the block is carved, trim the excess off with scissors to give it a straight edge, and then it is ready for printing. There are many different types of ink on the market, and it’s important to test them out to find the best one. Use oil-based inks because they give the best even coverage and print well on both fabric and paper, but there are lots of options out there. 5. The most important part is applying the pressure evenly, since the color will be stronger in some areas of the print than others if uneven pressure is applied. This is also a step that takes some practice and perfecting. 6. The ink then takes several days to dry, so unlike other printing processes, there is a long wait time before the prints are ready to use. The oil based inks can take from two days to a week to fully dry, whereas water-based inks will dry slightly faster.

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LAB EXPERIMENT 07 Name: _____________________________________________ _______________________

ID No.

Remarks:________________ Signature of the lab tutor_______________ Date:_________________

Screen Preparation

OBJECTIVES  To determine the different steps of screen preparation. MACHINES 

Engrave department

THEORY Screen-printing is the most flexible printing process. It can be used to print on a wide variety of substrates, including paper, paperboard, plastics, glass, metals, fabrics, and many other materials including paper, plastics, glass, metals, nylon and cotton. Some common products from the screen-printing industry include posters, labels, decals, signage, and all types of textiles and electronic circuit boards. The advantage of screen-printing over other print processes is that the press can print on substrates of any shape, thickness and size. PROCESS SEPERATING/ DESIGNING DEPARTMENT Separating department separates the colors which are made on the sample of papers, piece of fabric, in CD drive. There are following tasks of this department:  Set the repeat design  Open the congested design  Make pixels on design  Dots in the design of screen These all tasks can be done on adobe Photoshop or Ramsete-3 software’s. Supplier or costumer gives only their required design in cd format. In cd they also give a form in which following things are mention:  Number of ways on same design (deign is same but color change)  Number of screen required  Repeat size 20

 Screen width  Print direction

ENGRAVING DEPARTMENT This department makes the sheets for printing known as screens. There are two types of engraving 1. Rotary engraving 2. Flat engraving ROTARY ENGRAVING: Engraving means exposing of design on the screen. These screens are made of nickel. Following are parameters concern with screen:  Screen size (length): Screen size 1280 mm 1620 mm 1850 mm 2650 mm 3050 mm 3500 mm  Screen repeat (diameter):  64 mm  82 mm  91.4 mm  101 mm  Screen mashes:  20 /cm  40 /cm  60 /cm  80 /cm  125 /cm  135 /cm  135 /cm  155 /cm  165 /cm  195 /cm

Max. Fabric width processed 45” 60” 72” 94” 110” 130”

Gold, silver, white white and back side print Geometric, rafted effect, half tone and fine print same same same same same

Following is the sequence of process for exposing screen:  Chemical coating:  G.B.M used for chemical coating the screen.  This task is done on coating machine. 21

 The screen fixed in vertical form.  The chemical put on squeegee.  The squeegee diameter depends on screen diameter.  Time depends on screen length.  Speed of machine is 15-16 m/min for hard coating and 6-7 for light coating.  Climatizer Machine ( Dryer):  This machine is used for drying the chemical coating on screen.  Temperature is set 47-48 oC  Time= 10mins  Exposing machine: There are two exposing machines used in Popular Fabrics Mill: I. II.

Manual machine Ink-jet machine  Manual machine now a day’s, not used. Inkjet machine:  

CST Ink-jet machine 2011 model Time for exposing design on screen depends on design & length of screen.  After completing task, screen is brought into lighting machine in which light is given to screen. The design area becomes soft and remaining is hard.  8 round of lighting carriage are given to screen length & about 10-12 min time taken for this task.  Exposing & developing:  Screen is dip on bath containing water for 5-10 min.  After this screen is fixed on rod and pressurized water is giving and soft brush is rub on screen through that soft area or chemical is taken off from exposed area.  Ring machine:  Solid ring is fixed at both ends of screen which is fit on print machine.  Adhesive is applied for joining the rings with screen.  Polymer chamber:  This machine is used for drying the adhesive on screen.  Temperature= 220 oC  Time = 10 min

Test Results:

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Review Question: __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ ___________________________________________________________________________

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LAB EXPERIMENT 08 Name: _____________________________________________ _______________________

ID No.

Remarks:________________ Signature of the lab tutor_______________ Date:_________________

Hand screen printing of cotton fabric with pigments PERFORMANCE/OBJECTIVES  

Preparation of stock paste. Preparation of print paste.



To print given cotton fabric with the help of Pigments.

APPARATUS  Beaker  Stirrer  Electric Balance MACHINES USED  Flat bed printing machine  Stenter DISCUSION In pigment printing, insoluble pigments, which have no affinity for the fiber, are fixed on to the textile with binding agents in the pattern required. Importance of pigment printing Pigments, of course, are used for the production of plain-colored fabrics, but are of much greater importance in printing. 1. The pigment can be applied to all fibers potentially and it is the only coloration to glass fiber, fabric and polyester 2. No wet treatment is required, so drying and curing is applicable to all fiber. 3. Extensive color range of highly light fast colors 4. Possible to produce good combination shades on blended fiber in one padding operation 24

5. Application procedure is simple 6. Less expensive

CHEMICAL REQUIRED (for stock paste) 

Sodium Alginate

________



liquor Ammonia

________



Binder

________

 Water

________

PROCEDURE First of all, about 1liter of water was taken in a beaker followed by the addition of sodium alginate 3% and a small amount of ammonia liquor. This mixture was then stirred vigorously using a high speed stirrer. The viscosity of paste was then measured with the help of viscometer. The amount of PVA was optimized to obtain a viscosity level of 7000 centipoises using spindle no. 6 of the viscometer. In the next step, binder was added and again the viscosity was measured. The increase or decrease in viscosity was noted. A small amount of PVA was again added to get the required viscosity. CHEMICAL REQUIRED (for print paste) 

Stock paste

________



Pigment

________

PROCEDURE Pigment was added in the prepared stock paste and the paste was stirred for some time to make the pigment paste. PRINTING OF COTTON FABRIC PROCEDURE: The fabric sample was put on flat bed machine with the screen on the fabric. Print paste was put on one side of screen and applied with the help of steel rod. Steel rod moved with the help of electromagnetic assembly and applied the paste on the fabric. The fabric was then dried at 110oC for 1 min through stenter. It was then cured at 170 oC for 2 min. Testing was carried out on the fabric.

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Test Results: __________________________________________________________________________________ __________________________________________________________________________________ ___________________________________________________________________________

Review Question: __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ 26

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LAB EXPERIMENT 09 Name: _____________________________________________ _______________________

ID No.

Remarks:________________ Signature of the lab tutor_______________ Date:_________________

Lab-scale automatic flat screen printing of cotton fabric with reactive dyes

PERFORMANCE/OBJECTIVES  

Preparation of stock paste. Preparation of print paste.



To print given cotton fabric with the help of Pigments.

APPARATUS  Beaker  Stirrer  Electric Balance MACHINES USED  Flat bed printing machine  Stenter CHEMICAL REQUIRED (for stock paste)      

Dyes Urea Thickener Resist salt Soda ash Additional water

= = = = = =

4gm 10gm 50gm 1gm 6gm as required.

DICUSION By the term textile printing we mean the localized application of dyes or pigment and chemical by any method, which can produce particular effect of color on the fabric according to the design. In this practical we print cotton fabric with cold brand reactive dyes in block 27

and screen-printing methods in combination method. Block printing method is the oldest printing method. It is used mostly in sarees, handkerchiefs etc. in this printing method we use blocks of different designs. In screen printing a very little screen made by glass fibre is used. There are types of screen-printing, but we have done in our experiment was hand screenprinting. Handscreen-printing is mostly used for sarees to 14-16 colors in on pattern can be produced at a time.

Preparation of thickener: 1) 16 gm of starch and 200cc water are taken in bowl. 2) Heat is applied and solution is stirred continuously until a thick viscose solution is obtained. 3) By continuous stirring and boiling a specific viscosity is obtained. 4) The heat application is stopped otherwise viscosity falls down. So temperature is maintained strictly.

Preparation of printing paste: 1) At first we take required amount of dyestuffs in a bath. 2) Then little amount of water is added into the bath for mixing these dyes. And start stirring for mixing the three types of dye. 3) Then required amount of urea is added into the dye bath. 4) After then required amount of thickener is added 5) Then continuous stirring is done for few minutes for mixing all the ingredients of print paste. 6) After mixing finally required amount of alkali is added to the dye bath and mix them with the help of stirring.

PRINTING PROCESS: Block printing method: 1) The fabric which will be printed is placed on the printing table. 2) The printing paste is put on the tray box. 3) The block is selected and it is touched with print paste. 4) Then block is pressed upon the sample fabric. 5) After pressing the block on the sample fabric the block is put off from the fabric. 6) Finally we get the printed fabric of required dyes.

Screen-printing method: 1) The fabric is placed on the printing table of flat screen-printing machine. The table is made of soft by laying on it. 28

2) Then the screen is placed on the sample fabric. 3) The printing paste is taken on the screen perforation. 4) Thus we can find the printed fabric with a smooth wooden strike the paste is spread over the screen with slight pressure. 5) So that the dye particles can penetrate through the screen perforation. 6) Thus we get printed fabric.

After treatment: The printed fabric is steamed for 5-10 minutes in a cottages steamer and washed with cold water for removing unfixed dye and exhausted thickener and then dried.

Conclusion: Printing of cotton fabric with reactive dyes has excellent build up property and maximum fixation. Shade is also bright. By this experiment we have acquire knowledge about process of printing cotton fibres with cold brand reactive dyes in combination shade. The shade of printed fabric is moderately good, as we required. Special thanks to our teacher and his assistants for grate cooperation.

Test Results: __________________________________________________________________________________ __________________________________________________________________________________ ___________________________________________________________________________ 29

Review Question:

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LAB EXPERIMENT 10 Name: _____________________________________________ _______________________

ID No.

Remarks:________________ Signature of the lab tutor_______________ Date:_________________

Lab-scale automatic flat screen printing of polyester-cotton blended fabric with Pigment printing

PERFORMANCE/OBJECTIVES  

Preparation of stock paste. Preparation of print paste.



To print given cotton fabric with the help of Pigments.

APPARATUS  Beaker  Stirrer  Electric Balance MACHINES USED  Flat bed printing machine  Stenter CHEMICAL REQUIRED (for stock paste) 

Sodium Alginate

________



Ammonia liquor

________



Binder

________

 Water

________

PROCEDURE First of all, about 1liter of water was taken in a beaker followed by the addition of sodium alginate 3% and a small amount of ammonia liquor. This mixture was then stirred vigorously using a high speed stirrer. The viscosity of paste was then measured with the help of viscometer. The amount of PVA was optimized to obtain a viscosity level of 7000 centipoises using spindle no. 6 of the viscometer. In the next step, binder was added and again the viscosity was measured. The increase or decrease in viscosity was noted. A small amount of PVA was again added to get the required viscosity. 31

CHEMICAL REQUIRED (for print paste) 

Stock paste

________



Pigment

________

PROCEDURE Pigment was added in the prepared stock paste and the paste was stirred for some time to make the pigment paste. PRINTING OF COTTON FABRIC PROCEDURE: The fabric sample was put on flat bed machine with the screen on the fabric. Print paste was put on one side of screen and applied with the help of steel rod. Steel rod moved with the help of electromagnetic assembly and applied the paste on the fabric. The fabric was then dried at 110oC for 1 min through stenter. It was then cured at 170 oC for 2 min. Testing was carried out on the fabric.

Test Results: __________________________________________________________________________________ __________________________________________________________________________________ ___________________________________________________________________________

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Review Question:

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LAB EXPERIMENT 11 Name: _____________________________________________ _______________________

ID No.

Remarks:________________ Signature of the lab tutor_______________ Date:_________________

To determine viscosity of printing paste

PERFORMANCE/OBJECTIVES Upon the successful completion of this experiment, the students will be able to understand: (i) (ii)

The need for calculating viscosity of printing paste Working with digital viscometer

APPARATUS  Digital Viscometer  Printing Paste DISCUSSION Viscosity of printing paste is very important because it influences the clarity and appearance of printed pattern. It maintains sufficient elasticity and plasticity of film coating on the fabric after printing and not to flake or crack when dry.The capillary actions caused by the dye to run can also be prevented by maintaining viscosity. It also provides easy flow in the screen while printing operation is continued. Mostly the viscosity is maintained by using thickener and liquor ammonia or other alkalis. Thickeners are added to the printing past to produce viscosity which is necessary to ensure sharp definitions. If the viscosity of printing paste is high then “Haloing effect” fault is produced and if the viscosity of printing paste is high then “Flushing effect” fault is produced. According to the standard conditions for printing, the paste viscosity should be between 7000- 8500 mPa. PROCEDURE: 1. 2. 3. 4. 5.

Prepare printing paste as per recipe. Homogenously mix it. Turn on the viscometer. Select the spindle type to be used. Adjust speed of the spindle and enter the number of selected spindle on the control panel. 6. Start to the process and determine the viscosity values.

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Test Results: __________________________________________________________________________________ __________________________________________________________________________________ ___________________________________________________________________________

Review Question: __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________

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LAB EXPERIMENT 12 Name: _____________________________________________ _______________________

ID No.

Remarks:________________ Signature of the lab tutor_______________ Date:_________________

To determine rubbing fastness of pigment printed fabric by ISO 105 x 12 method

PERFORMANCE/OBJECTIVES Upon the successful completion of this experiment, the students will be able to understand: (i) (ii)

The need for determining rubbing fastness of printed materials ISO 105 X 12 method for checking rubbing fastness

APPARATUS   

Crock meter Rubbing Cloth Grey scale

DISCUSSION Loss of color when textile material is rubbed against various surfaces is known as lack of color fastness to rubbing. Reason for poor rubbing fastness is loosely held dye molecules on the surface of the fabric. Crock meter is the apparatus used to determine rubbing fastness of dyed or printed textile materials. Fabric are tested for checking their rubbing fastness using wet and dry rubbing cloth, called wet rubbing and dry rubbing respectively. Rubbing cloth used for this purpose is 5 x 5 cm desized and bleached cloth on which few drops of water are pored in case of wet rubbing, otherwise dry cloth is used. PROCEDURE: 1. Cut two pieces of fabric to be tested having their dimensions not less than 14 x 5 cm. 2. Fasten the samples on the baseboard of crock meter with the help of clamps. 3. To determine rubbing of multi-colored fabric fix and check rubbing of each color separately. 4. With the dry rubbing cloth flat in place over the end of finger of testing device, rub to and fro in a straight line along a track 10 cm long on the dry specimen at 10 cycles per 10 second downwards force of 22N or 9N. 5. Repeat the process for wet rubbing with a fresh dry specimen and with a rubbing cloth that has been wetted with water by placing it on the grating and dropping evenly on it its own mass of water or use any method to ensure a take-up of about 100%. After rubbing dry the cloth at room temperature. 6. Asses the staining on the rubbing cloth using grey scale. 36

Test Results: __________________________________________________________________________________ __________________________________________________________________________________ ___________________________________________________________________________

Review Question: __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________

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LAB EXPERIMENT 13 Name: _____________________________________________ _______________________

ID No.

Remarks:________________ Signature of the lab tutor_______________ Date:_________________

Digital printing of textiles

PERFORMANCE/OBJECTIVES 

Introduction and importance of Digital Printing

DISCUSION  First digitized manufacturing process involved textiles-Invention of Joseph Marie Jacquard in 1801.  That device was able to weave complex designs.  Information was carried onto punched cards.  Opportunities arose to apply these technologies to textile printing.  Provided a spring board for product innovation.  First digital printing on carpet by Millikan (patented).  Textile digital printing evolved in 1990s as a prototype tool for printing small batches of fabrics for niche production.

COMPARISON OF ROTARY SCREEN AND DIGITAL PRINTING METHODS

Digital method

conventional method

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Features Digital Printing of Textiles  Flexibility  Reduced setup  costs  Small batches  Variable data  Design freedom  Process enhancement  Low waste  Customised products  Design innovation  No stock  Innovation  Novel inks  Product security  Nanotechnology

MACHINES USED Dream ink jet printer  Printing Speed 150- 190 Sq. m /hr.  Fabric width 150 cm.

DuPont 3210    

Speed 30 -60sq m / h Width 3.2 meter 360 dpi (Good quality) 8 color system

DuPont 2020    

Speed 30 sq m / Hr. Width 1.8 M 720 dpi 8 color process

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Test Results: __________________________________________________________________________________ __________________________________________________________________________________ ___________________________________________________________________________

Review Question: __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________

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