LESSON 6 BLOCK PRINTING: PRE-AND POST-TREATMENTS STRUCTURE 6.0
OBJECTIVES
6.1
INTRODUCTION
6.2
SELECTION OF THE FABRIC
6.3
PRE-TREATMENT OF FABRIC
6.4
PREPARATORY PROCESS FOR W OODEN BLOCK
6.5
STEPS TO BE TAKEN BEFORE PRINTING
6.6
POST-TREATMENT OF FABRIC
6.7
QUALITY PARAMETERS
6.8
ASSIGNMENTS 6.8.1 CLASS ASSIGNMENT 6.8.2 HOME ASSIGNMENT
6.9
SUMMING UP
6.10 POSSIBLE ANSWERS TO SELF-CHECK QUESTIONS 6.11 TERMINAL QUESTIONS 6.12 REFERENCES AND SUGGESTED FURTHER READING 6.13 GLOSSARY
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6. BLOCK PRINTING: PRE - AND POST -TREATMENTS In Lesson 4, the historical background of block printing was first given followed by a description of the types of blocks used and how they are made. In Lesson 5, the materials and tools used were first listed followed by brief description of print paste or dye paste formulation and the block printing process. In this lesson we will describe some pre- and post-treatments which will lead to superior performance.
6.0
Objectives After going through this lesson, you will gain an understanding of:
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What constitutes an appropriate fabric for block printing
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Pre-treatment of fabric
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Preparatory process for wooden blocks
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The steps to be taken before printing
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Post-treatment of fabric
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Quality parameters
6.1
Introduction
Although we have earlier discussed the process of block printing in some detail, there are some important issues that need attention. These are mainly concerned with the choice of a suitable fabric and their pretreatment, pretreatment of wooden blocks to enhance their working life and post-treatment of the fabric to fix the print. These various issues have to be taken care of by proper planning, preparation and precautions before and after the printing phase so as to accomplish any block printing project satisfactorily and successfully. This lesson will deal with these various practices which lead to quality output.
6.2
Selection of the Fabric
The print paste formulations based on pigment colours and dyes that have been described in lessons 5 and 14 are suitable for printing fabrics based on natural fibres, which include cotton, organdie, and chiffon silk. They are not suitable for the printing of fabrics based on synthetic fibers.
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6.3
Pre-treatment of Fabric
It is essential to remove the starch that may be present in the fabric to be printed before we start printing. To remove the starch dip the fabric in cold water in which small amount of detergent has been added. Allow the fabric to soak water for 24 hours after which take out the fabric and wash it with cold water. After drying the fabric, iron it well. Now the fabric is ready for printing.
6.4
Preparatory Process for the Wooden Blocks
Before starting the work, the wooden blocks are dipped in mustard oil for 48 hours (Fig. 6.1), so that wood absorbs the oil. This is to ensure that the block does not deteriorate soon as the blocks have to be cleaned several times with water and since wood swells in water, it may soon disintegrate through fibrillation. Dipping the block in the oil ensures that the wood does not absorb water during the cleaning step, thus adding to the useful lifetime of the block and also ensuring that the block does not change shape. After treatment the blocks are removed from oil and placed on a newspaper for a whole day. The newspaper absorbs the extra oil in the block. Before the actual printing, a trial print on some rough fabric should be done, so that the extra oil in the block comes out and does not affect the final product.
Fig. 6.1 Pre-treatment of Block
6.5
Steps to be taken before printing
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First cover the wooden table with woollen cloth, to give resilience and provide a water resistant top. The cloth absorbs any colour which penetrates into the underside of the fabric and thus avoids staining of the printed fabric..
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The next step is to prepare the print paste according to the recipes given in lessons 5 and 14.
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The fabric to be printed is laid on the table in a stretched, creaseless condition.
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Three to four layers of foam sheet are placed in the tray before pouring the colour over it. These soak the colour which can then be conveniently transferred to the design on the wooden block.
Self-check Questions 1. What do you understand by Pre-treatment of a Fabric? 2. What are the steps to be taken before printing?
6.6
Post-treatment of Fabric
After printing, leave the fabric for drying. Then the print may be fixed by dry heat in a drying chamber or by keeping the fabric in the reverse position in the Sun. Finally the fabric is ironed from the backside.
6.7
Quality Parameters The main important quality parameters for block printing are listed below:
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There should be perfect alignment in successive positions of the block.
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Colour should be spread evenly on the foam sheet.
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Fabric should be in a creaseless form.
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The blocks must be cleaned immediately after the printing with the help of a toothbrush, so that they are ready for further use.
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The printed side of the fabric should not be exposed to the Sun while drying. Otherwise the colours can fade.
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The fabric should not be washed immediately after printing. The prints should be allowed to dry first.
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6.8
Assignments
6.8.1 Class assignments i)
Visit a block printing unit and observe carefully how the various things you have learnt are actually put into practice.
6.8.2 Home Assignments
i)
Write down your observations about the block printing unit you have visited.
6.9
Summing Up
In this lesson, we have learnt that fabrics based on natural fibres are more suitable for printing using the formulations described. The various preparatory processes for the fabric and the blocks have also been briefly described. Finally post-treatment steps along with quality parameters were briefly discussed.
6.10 Possible Answers to Self-check Questions 1. Pretreatment of fabric: Dip the fabric in cold water in which a small amount of detergent has been added. Allow the fabric to soak water for 24 hours after which take out the fabric and wash it with cold water. After drying the fabric, iron it well. Now the fabric is ready for printing. 2. Steps to be taken before printing: i)
First cover the wooden table with woollen cloth, to give resilience and also provide a water resistant top. The cloth absorbs any colour which penetrates into the underside of the fabric
ii)
Spread the fabric to be printed on wooden table in stretched, creaseless condition.
iii) Put three to four layers of foam sheet in the tray before pouring the colour over it.
6.11 Terminal Questions 1. What are the quality parameters for block printing? 2. Which kind of fabric is appropriate for colouring with Acramin pigment colours? 3. What are the necessary arrangements which should be made before we start block printing? 6
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6.12 References and Suggested Further Reading 1. Hatanaka, K. 1996. Textile Arts of India. Chronicle Books, New York. 2. Kothari, G. 1995. Colourful Textiles of Rajasthan. Jaipur Printers Pvt. Ltd., Jaipur. 3. Mehta, R. J. 1984. Masterpieces of Indian Textiles. D.B.Taraporevala Sons & Co. Private Ltd., Bombay. 4. Singh, M. 2000. Handcrafted Indian Textiles. Roli Books Pvt. Ltd., Mumbai.
6.13 Glossary 1. Disintegrate
Break into parts or components
2. Mustard Oil
An edible oil Obtained from mustard seed
3. Natural
Derived from nature
4. Resilience
Flexibility
5. Starch
Sizing material used to stiffen the fabric
6. Synthetic
Artificial, Derived Chemically
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