LESSON 14 SCREEN PRINTING: TOOLS USED AND THE PROCESS STRUCTURE 14.0 14.1 14.2
OBJECTIVES INTRODUCTION TOOLS AND MATERIALS USED IN SCREEN PRINTING 14.2.1 14.2.2 14.2.3 14.2.4 14.2.5 14.2.6
14.3
THE PRINTING PASTE 14.3.1 14.3.2 14.3.3
14.4
SCREEN COATING METHOD
CLEANING THE SCREEN ASSIGNMENTS 14.9.1 14.9.2
14.10 14.11 14.12 14.13 14.14
CHALK LINE A BORDER BORDER REPEATED TO CREATE AN ALL OVER DESIGN AN ALL OVER DESIGN BEFORE STARTING TO PRINT
PREPARATION OF SCREEN 14.7.1
14.8 14.9
PREPARING THE FABRIC FOR SCREEN PRINTING
MARKING THE FABRIC BEFORE PRINTING 14.6.1 14.6.2 14.6.3 14.6.4 14.6.5
14.7
BRIGHT COLOURS DULL COLOURS PASTEL COLOURS
THE FABRICS 14.5.1
14.6
PREPARATION OF EMULSION THICKENER OR BINDER PASTE RECIPE FOR PRINTING PASTE MIXING YOUR OWN COLOURS- COLOUR W HEEL
COLOUR COMBINATIONS 14.4.1 14.4.2 14.4.3
14.5
FRAMES BOLTING CLOTH SQUEEGEE PRINTING BASE DRYING RACK OR LINE OTHER BASIC EQUIPMENT
CLASS ASSIGNMENTS HOME ASSIGNMENTS
SUMMING UP POSSIBLE ANSWERS TO SELF-CHECK QUESTIONS TERMINAL QUESTIONS REFERENCES AND SUGGESTED FURTHER READING GLOSSARY
14. SCREEN PRINTING: TOOLS USED AND THE PROCESS After obtaining knowledge about the basics of screen printing in lesson 13, one needs to learn about the tools and equipments required for the process. One also needs to understand the process so that he/she can create designs through screen printing with ease and perfection. Both these aspects are dealt with in this lesson.
14.0 Objectives After going through this lesson you will be able to: •
Assemble the tools and equipments for the project.
•
Make the printing paste by yourself.
•
Decide how you are going to place a design on your fabric piece with screen print for example all over repeat or a border repeat etc.
•
Set-up a screen printing project.
14.1 Introduction Screen printing is a simple ornamentation technique of surface designing for embellishment of fabric with the help of a simple stencil or screen through which colour is passed, with a design on its surface. This process is a very widely used in India for creating attractive designs. The equipments can be automatic, semi-automatic or manual. The manual process is very popular in India and provides jobs to a large number of people. It is of utmost importance that the right tools and the right process are used to create designs on fabrics. This lesson deals with the following aspects of Screen Printing: •
Tools used in screen printing
•
Fabrics that can be used for screen printing
•
The printing paste
•
Mixing of colours
•
Marking the fabric before printing
•
Preparation of screen/screen coating method
•
Cleaning the screen
14.2 Tools and Materials Used in Screen Printing 14.2.1 Frames A frame (Fig. 14.1) is invariably used in manual screen-printing. The frame serves the purpose of holding the bolting cloth or silkscreen in a tight position as well as a basin for holding the paste while printing. The frame is usually of rectangular shape and its size has to be a few centimeters more than the size of the print desired. There is no hard and fast rule about this. The idea is that sufficient paste is held at one end, to be taken to the other by the squeegee, covering the entire area to be printed.
Fig. 14.1 Frame
The frames must be made of good quality seasoned, knot-free wood. Metal frames are mostly used where rigidity is necessary for quality production e.g. in mechanized screen-printing. 14.2.2 Bolting cloth Screens may be made using cotton organdie stretched on a wooden frame. Such screens are very primitive, but for a beginner they are adequate. For professional use polyester mesh (Fig. 14.2) is sold by the meter by screen-printing suppliers. This is a fine gauze mesh of man-made fabric. Earlier the mesh used to be made of silk hence the term ‘silk screening’, which is still in common use today. Mesh numbers can range from very coarse (30) to fine (90) and then to ultra fine. The numbers indicate Fig. 14.2 Bolting cloth the number of threads per 2.5 cm [1 inch]. Screens using higher mesh count fabric produce very sharp prints with small and fine details. The paste consumption will also be less, and reverse the case with screens of lower mesh counts. Good quality printing will result from a properly stretched and prepared screen, especially when multi-colours are used in the process, so prime importance should be given to this aspect during screen preparation. 14.2.3 Squeegee This is a blade of rubber or plastic, attached to a wooden handle and used for pushing the printing paste over the surface of the mesh. It is the pressure Fig. 14.3 Squeegee
that is applied to the squeegee that pushes the printing Paste through the mesh and onto the fabric beneath. The squeegee selected for a particular job (Fig. 14.3) should be at least 1.5” wider than the width of print or design taken in hand. Also its width should be less than the inside width of the frame by about the same margin of 1.5”. This will allow for a side play of Squeegee inside the frame while printing is carried on. The rubber used for making this tool should have appropriate flexibility or hardness and be resistant to the various chemicals in the printing paste. The higher the hardness, the less flexible the squeegee will be, and so will require more pressure. This can, however, give finer and sharper prints. The Squeegee blade should be maintained and trimmed with a sharp square edge. A thorough cleaning is necessary after each printing job when storing it for subsequent use. A piece of sand paper nailed to a block of wood will help to sharpen the rubber edges when they become round and blunt in course of time. 14.2.4 Printing base Any flat surface can be used as long as it does not wobble. The bigger the surface, the better it is, as it is easier to print large pieces of fabric. A dining table or a table tennis table can easily be converted into a temporary printing-table by covering them with a thin piece of foam rubber as large as the area to be used for printing and with a couple of bed sheets to cover it. These can be removed after a printing session. If, however, you are going to do more than an occasional print, you will need a special table in order to work with long lengths of fabric and also to avoid having to tidy them up every time. To prevent the fabric from moving around while you print the material to be printed can be fixed with the help of pins. 14.2.5 Drying rack or line The printed fabric or made-up dresses need to be hung out, For long fabric or saris, rows of plastic or wire lines are best suited, and racks for drying the made ups. The time required for drying and curing may depend on various factors related to the weather (e.g. temperature, humidity, circulation of air and the Sun). 14.2.6 Other basic tools •
Craft knife, ideal for cutting out paper stencils.
•
Sheet glass (Fig. 14.4), useful for resting paper stencils on when cutting them out with a craft knife. A piece of hardboard can also serve this purpose well or a wad of newspapers can be used instead.
Fig. 14.4 Glass
•
Packaging tape used to reduce the size of the printing area of the screen and as a ‘resting place’ for the paste before and after it has been pushed across the screen. (This tape is 2 inch wide and is a brown, extra sticky type of Scotch tape. It is not to be confused with rolls of gummed brown paper.)
•
Soft lead (HB) pencil used for marking the mesh. (A hard lead will damage the mesh.)
•
Metal or wood Ruler
•
Set square.
•
All-purpose scissors.
•
Paint brushes 1” wide, with the length of the bristles shortened by half to create firm, sturdy applicators. These are used for applying textile printing paste to narrow areas of printed fabric.
•
Watercolor brushes, a sable or imitation sable brush (size 4) for design work on the screen or on tracing paper.
Self-check Questions 1. List the tools and equipments that are used for screen printing process. 2. What is meant by the term bolting cloth? 3. What is mesh count or mesh number? 4. What is a squeegee?
14.3 The Printing Paste The print formulation, which must be non-toxic, has to be carefully worked out. To ensure a sharp fine print with clear edges, the colours must be held in position without spreading. A thick paste containing the colour (dye or pigment) prevents migration of the colour and the paste holds the colour till it is fixed after printing. The success of screen-printed fabric depends as much on the mixing of colours as on the design. You will find that suppliers carry a wide range of colours, but if you are just starting it would be best to begin with four basic colours. These are Red, Blue, Yellow and Black; and from them virtually any colour can be prepared by mixing. The printing paste may be based on the use of pigment colours or of dyes; the former being more in use for Screen Printing, Acramin pigments are widely available along with
Acramin SLN binder. For making a print paste formulation from this pigment–binder combination, an emulsion thickener or binder paste is first made as an intermediate product. A formulation based on this product combination for printing of cotton fabrics will now be described:
14.3.1 Preparation of emulsion thickener or binder paste The binder (10% SLN) is the intermediate product, which is prepared first. It is then used to prepare the paste. Preparation of 10% Acramin SLN (Emulsion thickener) 10 parts
Acramin SLN
3-6 parts
Low viscosity CMC thickener
2-3 parts
Urea
6-3 parts
Water
79 parts
Kerosene added slowly under high speed stirring
Note: Soak overnight low viscosity CMC (Carboxy Methyl Cellulose) Thickener in water (Take 5 parts CMC to which add 100 parts water) 14.3.2 Recipe for printing paste The recipe of printing paste depends upon the shade required.
Colour/shade
Lemon yellow
medium shade
Dark shade
Black/dark yellow
Acramin pigment(colour)
1
3
5
7
10% Acramin SLN (emulsion thickener)
93
91
89
81
Acramin SLN
-----
-----
3
9
Water
3
3
-----
---
Parts of
Diammonium phosphate solution 1:3 water (Catalyst)
3
3
3
3
Colour fixing is done by curing the goods, subjecting them to dry heat treatment at 140 degrees celsius for 5 minutes after printing and drying. 14.3.3 Mixing Your Own Colours - Colour Wheel (Fig.14.5): From the three basic colours (Red Blue, Yellow) you will first need to mix three secondary and six tertiary colours in order to have in stock the 12 colours in the colour wheel. Using these, try a few exercises in colour mixing and make a set of colour swatches i.e. samples of cloth to help you in planning colours for future screen printing projects. Fig. 14.5 The colour wheel
Set aside 12 x 500 ml jars, with air tight lids, in which, to mix your printing paste.
14.4 Colour Combinations When measuring your colours, it is not critical to measure precisely to the last drop, but it is important to be consistent, so that when you need to remix a colour it will be the same. Stir the printing paste thoroughly together until there are no streaks. Then, once you have mixed a colour, label it. It is very frustrating if you cannot find a colour and have to re-test them all in order to find the right one. To make secondary and tertiary colours, mix the following: •
Yellow in a small container(Fig. 14.6) o Green - mix Yellow with Blue (50-50%). o Lime-green - mix Yellow with Blue (75-25%). o Deep green - mix Yellow with Blue (25-75%).
•
Blue in a small container. o Violet - mix Blue with Red (50-50%). o Reddish Violet - mix Blue with Red (25-75%).
Fig. 14.6 Yellow
o Bluish Violet - mix Blue with Red (75-25%). •
Red in a small container(Fig. 14.7) o Orange - mix Red with Yellow (50-50%). o Reddish Orange - mix Red with Yellow (75-25%). o Yellowish orange- mix Red with Yellow (25-75%). Fig. 14.7 Orange
Take 12 squares of cotton fabric and sponge on each of the 12 colours. (Just dip a piece of sponge into a colour and wipe it over the square, then smooth it with the sponge until it is even and there are no ridges on the surface. When the colours are dry, iron to set them, then write the formula for each colour on the back of the relevant Square from 1 to 12). From these 12 colours an incredible range can be mixed.
Activity 1. Draw a colour wheel filled with primary, secondary and tertiary colours. 14.4.1Bright colours While mixing colours when it looks too bright, always add to it a little of the colour that appears opposite it on the colour wheel, i.e. its complementary colour. For example, if a turquoise (no 5) looks too intense, add a tiny quantity of orange. The colour becomes less bright and subtler, but it still remains distinctly turquoise. Exercise 1: Try the exercise below to see what happens to colours when a little of a colour’s complement is added: •
Mix (2 tbsp) of colour no 1(Yellow) with (½ tsp) of colour no 7(Violet)
•
Mix (2 tbsp) of colour no 2 with (Lime-green) (½ tsp) of colour no 8. (Reddish violet)
•
Mix (2 tbsp) of colour no 3 (Green) with (½ tsp) of colour no 9. (Red)
•
Mix (2 tbsp) of colour no 4 (Deep green) with (½ tsp) of colour no 10. (Reddish orange)
•
Mix (2 tbsp) of colour no 5 (Blue) with (½ tsp) of colour no 11. (Orange)
•
Mix (2 tbsp) of colour no 6 (Bluish violet) with (½ tsp) of colour no 12. (Yellowish orange)
•
Mix (2 tbsp) of colour no 7 (Violet) with (½ tsp) of colour no 1. (Yellow)
•
Mix (2 tbsp) of colour no 8 (Reddish violet) with (½ tsp) of colour no 2. (Lime Green)
•
Mix (2 tbsp) of colour no 9 (Red) with (½ tsp) of colour no 3. (Green)
•
Mix (2 tbsp) of colour no 10 (Reddish orange) with (½ tsp) of colour no 4 (Deep green)
•
Mix (2 tbsp) of colour no 11 (Orange) with (½ tsp) of colour no 5. (Blue)
•
Mix (2 tbsp) of colour no 12 (Yellowish orange) with (½ tsp) of colour no 6. (Bluish Violet)
Sponge the colours onto 12 more cotton squares. When the colours are dry, iron to set them, then write the formula on the back of each and number them from 13 to 24. 14.4.2 Dull colours Exercise 2: Mix 2 tbsp of a colour with 1 tsp of its complementary colour. For example, mix (2 tbsp) of colour no. 1 (yellow) with (1 tsp) of colour no. 7 (navy blue). Remember to write the formula on the back of each square and number them from 25 to 36. 14.4.3 Pastel colours Exercise 3: To each of the 12 colours of the colour wheel add four parts of clear base to give you colours 37 to 48. Then add four parts of clear base to one part of each of the jewel colours to obtain soft and different pastels (colours 49 to 60). You now have your 12 main colours from which you have mixed a further 48. If you like earthy colours, try adding more of each colour’s complement. If you enjoy working with pastels, try adding varying amounts of clear base to all the colour wheel, jewel and duller colours. The possibilities are endless. Always write the formula on the back of the swatch you have created so that you will be able to remix the colour.
Self-check Questions 5.
When colours look very bright, what should you mix with it?
6.
What is the full form of CMC?
14.5 The Fabrics Textile printing colours are effective on natural fibres, but always prefer to print onto 100% cotton. This, however, is a purely personal preference. If you are printing onto calico, be sure that it is pure cotton as some makes of calico have at least 50% synthetic. To test for synthetic (polyester) content, burn a little piece of fabric. Cotton burns readily without melting and leaves ash, while polyester shrinks away from flame and burns slowly, giving off a sweet smell of ester and leaves a hard, gray plastic residue. Cottons print well, absorbing any excess printing paste, which, on other fabrics, would remain on the surface and result in an uneven print. When made up they drape particularly well. 14.5.1 Preparing the fabric for screen printing Cotton fabric is available in the market ready for printing or dyeing. This is useful as washing and ironing of long pieces of raw fabric is tedious. The normal cotton fabric must first be washed in cold water to remove the starch and then in hot water (above 60°C) to shrink it. Using a washing machine, wash the fabric twice on a cold cycle and then, with detergent, on a hot cycle. Alternatively, if you do not have a washing machine, soak the material over- night in soap water and rinse and dry in the morning for shrinkage to be effective. To remove all the creases from pure cotton, always iron the fabric when it is damp. Spread the fabric on the printing table and smooth it out with the palm of your hand, making sure that the warp and weft of the fabric lie at right angles to each other. While smoothing out the fabric, feel for any foreign objects underneath the cloth that could cause printing irregularities or damage to your screen. Even if everything is straight, lift up the material again to remove even the slightest lump or ridge.
Activity 2. With the theme “Geometrical pattern for a bed sheet’’, think of 10 design ideas and chart out a final design from this and prepare the screen for this design.
14.6 Marking the Fabric before Printing This is the method of putting the screen down in exactly the right place on the fabric. You can position the screen by peering through the mesh, and it works quite well
until the screen becomes darkened by the ink. Therefore, it is better to mark out the fabric with a chalk line (Fig. 14.8). 14.6.1 Chalk line Using what is popularly known as tailors chalk, the string is coloured and placed along the fabric on the printing table. Stretching the string tight, a finger is placed firmly on each end, while a third hand is enlisted to pluck the string up at a more or less central point. When released with a snap, the string deposits a neat, straight line on the fabric.
Fig. 14.8 Chalk line 14.6.2 Border repeat The following two methods can be used: •
Method 1 o Mark a chalk line along the length of the fabric where the lower edge of the design will be printed. o Lower the screen into its first printing position on the left-hand side of the fabric (it is possible to see through the mesh to position it correctly on the chalk line) and mark the frame of the screen at the two points where it crosses the line. o To position the screen correctly for subsequent prints, look through the mesh until you can see the right-hand side of the previous print, and put the screen down so that there is a ½ inch overlap. Check that the marks on the frame are touching the chalk line as this keeps the border straight, and then print (Fig. 14.9).
Fig. 14.9 Border repeat, Method 1
•
Method 2 o Place the screen on the left-hand side of the fabric and measure the width of the design. Then, using a tailor’s chalk, and starting from the extreme right hand edge of the screen, marks off the width of the design along the entire length of the fabric. After making the first print, move the screen so that the first mark on the fabric lines up with the outer right-hand edge of the screen. This means that each section is printed with the screen touching the wood at the bottom, as well as one of the marks on the fabric on the right-hand edge of the screen (Fig. 14.10).
Fig. 14.10 Border Repeat, Method 2
14.6.3 Border repeated to create an all-over design Using the first method of registration with the chalk line, the border can be repeated close together to create an all-over design (Fig. 14.11).
Fig. 14.11 An all over design
14.6.4 An all-over design Every design has two dimensions - width and height. Mark off one of these dimensions along both selvedges of the fabric (i.e. the edges of a fabric that is woven so that they will not ravel or fray) and the other along both cut ends. Then join the opposite marks by means of chalk lines to form a grid over the fabric.
Initially it will be possible to print the material by simply looking at the chalk lines through the mesh, but after many prints, particularly when printing in black, the build-up of the printing paste will make it increasingly difficult to see clearly. Before starting to print, therefore, place the screen on the fabric and line up a square with the design on the screen. The chalk lines will intersect each side of the frame in two places. Mark these eight points clearly on the frame. Now the screen can be put down accurately in any square just by lining up the marks on the outside of the frame with the chalk lines.
Self-check Questions 1. Why one should wash the cotton fabric in cold water first and then in warm water followed by ironing while it is still damp? 1. What is the use of a chalk line? 14.6.5 Before starting to print •
Have a damp cloth ready for wiping your hands. Soiled fingers invariably leave smudges on the fabric.
•
Decide where to rest your Squeegee in between prints. If you leave it in the screen it always slides into the Paste. (It is not necessary to wipe the Printing paste off each time, as it does not drip.)
•
Have a pile of newspapers cut and ready to place on wet printing paste.
14.7 Preparation of Screen • Cut the mesh 10 cm (4”) larger than the frame all round. (This is necessary in order to get a good grip on the mesh when stretching it.) • Secure one side of the mesh with a Thumb pin in the middle of one side of the frame. Pull the other side of the mesh as tightly as possible without tearing it and pin it to the opposite side. • Now pin both sides of the mesh alternately, again keeping it as tight as possible. (You will need some help with this. Even so, there will still be a few wrinkles but these should disappear when the mesh is stretched in the opposite direction.) Fig. 14.12 Preparation of Screen
•
Starting at the centre of the other two sides, pin the mesh in the same way.(Fig.14.12)
•
Finish the screen by turning the excess mesh under, and pinning it down.
14.7.1 Screen coating method • After fixing the screen (by covering the frame with mesh), draw the design on to the screen with the help of pencil. • After tracing the design, apply enamel paint on the screen with the help of a flat brush, leaving the design portion. • Cover the entire screen (excepting the design portion) with enamel carefully (Fig.14.13), so that pores may not be left open. Fig. 14.13 Enameling the screen
•
Leave the screen for drying the enamel.
•
After drying, wash the screen with water
and let it dry.
14.8 Cleaning the Screen If some enamel is left on the design portion, clean it immediately with urea water, otherwise it will block the design.
14.9 Assignments 14.9.1 Class assignments i) List and sketch the tools used in screen printing. 14.9.2 Home assignments i) Draw the colour wheel and make different colour combinations.
14.10
Summing Up The following is a summary of what was covered in this lesson:
14.11
•
Printing pastes have excellent flow properties, depending upon the viscosity of the paste.
•
Coat the screen first from outside and then immediately from inside. After the final coating is over, the screen should be dried in horizontal position.
•
Immerse and keep the screen in cold-water bath for about 5-10 minutes. Wash the screen thoroughly by spraying water.
•
Avoid washing with sponge or wet cloth while cleaning dry screen properly.
Possible Answers to the Self-check Questions 1. Tools and materials used in screen printing are frames, bolting cloth, squeegee, printing base, drying rack or line, craft knife, ideal for cutting out paper, stencils, sheet glass, packaging tape, soft lead (HB) pencil, metal or wooden ruler, set square, watercolor brushes, paint brushes, all-purpose scissors. 2. Bolting cloth is a fine gauze mesh of man-made fabric which is stretched and bolted on a wooden frame to serve as screen for printing. 3. The mesh numbers indicate the number of threads per 2.5 cm [1 inch] of the fabric to be used as bolting cloth for screen. Mesh numbers can range from very coarse (30) to fine (90) and then to ultra fine. Screens using higher mesh count fabric produce very sharp prints with small and fine details. 4. A Squeegee is a blade of rubber or plastic, attached to a wooden handle and used for pushing the printing paste over the surface of the mesh. 5. To reduce the brightness we have to add the complementary of that colour lying opposite to it on the colour wheel. 6. Carboxy Methyl Cellulose. 7. The normal cotton fabric must first be washed in cold water to remove the starch and then in hot water (above 60°C) to shrink it. Ironing is done to remove all the creases from pure cotton.
8. The chalk like is made to mark on the fabric, the position along which the repeat prints are to be made with screen. It serves as a guide line for proper placement of the screen.
14.12 Terminal questions 1.
How will you create an all over design by screen printing?
2.
Explain the screen coating method.
3.
Explain the making of lighter, brighter, dull and pastel shades for printing.
4.
How screen is prepared for printing.
5.
Describe the print paste formulation briefly.
14.13 References and Suggested Further Reading 1.
Bhatnagar, P. 2000. Screen Printing Techniques for Unemployed Women, Ministry of SSI & ARI, Govt. of India, New Delhi.
2.
Kafka F. J. 1959. Batik, Tie Dyeing, Stenciling, Silk Screen, Block Printing: The Hand Decoration of Fabrics. Dover Publications, Inc., New York.
3.
Russ, S. 1964. Fabric Printing By Hand. Studio Vista Limited.
4.
Stallebrass, P. 1990. The Creative Guide to Fabric Screen Printing. New Holland Publishers Ltd.
5.
Anonymous. 1920. Fancy Designs. The Pepin Press, Milan.
6.
Clarke, W. 1974. An Introduction to Textile Printing. 4th Ed. Newness Butterworth, U.K.
14.14
Glossary
1.
Beneath
Under
2.
Complementary
Opposite
3.
Consistency
Evenness
4.
Consumption
Use
5.
Converted
Changed
Educated
6.
Dimensions
Size
7.
Embellishment
Decoration
8.
Humidity
Moisture content
9.
Increasingly
More and more
10.
Incredible
Unbelievable
11.
Non Toxic
Safe
12.
Obtainable
Available
13.
Organdie
Fine cotton fabric
14.
Released
Free
15.
Relevant
Being related
16.
Required
Necessary
17.
Ridge
A raised strip
18.
Scotch Tape
Sticking plastic tape
19.
Sponge
A porous, absorbent object, Wipe
20.
Squeegee
Rubber blade with wooden Handle
21.
Stretch
Extend, lengthen
22. Subsequent
Following
23. Sufficient
Enough
24. Temperature
Measure of heat
25. Treatment Virtually
Handling Almost