Hand screen printing is a common technique that has been carried out for years in the textile pockets of the country. It is essentially a stencil process. An open mesh fabric is used to hold in place the ‘islands’ of the stencil design through which inks are forced using a flexible blade of rubber or polyurethane called a squeegee.
History of Hand Screen
Screen printing is not a very old process. Some of the earliest applications can be found in medieval Japan. It appeared in Europe in the 18th century, particularly in France for stenciling patterns on to fabric In the 19th century it remained a simple process using fabrics like organdy stretched over wooden frames. Only in the twentieth century did the process become mechanized, usually for printing flat posters, packaging and fabrics. It became widely used to print colored wallpaper as a cheaper alternative to printing with wooden blocks.
Regions Known For Hand Screen Printing in India
The Gujarat region has been one of the great textile exporting regions of the country. The patterns were usually applied by block printing. Originally there were three types of hand printing – ajrakh, block and screen. The block printed and screen-printed designs produced in Ahmedabad comprise a variety of floral sprays and simulated bandhani (tie-and-dye) on a red background. The floral prints have a strong Persian influence.
The first stage in the process of screen printing is the procurement of the fabric straight from the mills. Screen printing can be done on a whole range of fabrics. It can be done on cotton, jute, silk, polyester and any many more. The below mentioned fabrics are the most common used for screen printing –
There are two main type of dyes used for printing:
Vat dyes are reasonably transparent and so secondary and tertiary colours can be made by the successive printing of one color on top of another. There is greater control on the results when printing light to dark colours. These dyes yield the softest hand (the “hand” is the feel of the fabric) and maintain the fabric’s luster. The color goes through a chemical reaction and actually becomes part of the fabric. These are mainly used for Discharge and Procion printing processes.
Vat dyes are liquid dyes.
The following are also required:
Pigment dyes are much more economical to use. Pigments are generally more lightfast, and give greater color control. Pigment dyes are applied like a coating on the cloth (i.e.) the dye does not seep into the cloth as in Vat dyes. Hence, the color of the pigment must be a tone darker than the base cloth color to get best results.
There are three types of pigments in use:
The pigment dyes could be oil based or water based. Oil based dyes are readily available. The water-based paste has to be made with a ratio of 2 kg paste dissolved in 80 l of water. 2% of glycerin or pen oil and retarder are also added for good color slippage and even spread of color while screening. The inks and dyes need to be stored so that they do not freeze, or they will break down and be useless.
Raw Material Procurement
The raw fabrics are mainly procured from large textile mills in Ahmedabad; Century Mills and Anglo French Mills in Pondicherry; Tirupati Mills and others from Bombay and Rajasthan. All the three main fabrics procured: sheeting, canvas and voile are 100% cotton. They are called as ‘Gray’ fabrics before the pre-dyeing stage. They are stored in the ‘Gray room’ where the fabric is first checked on lighted glass tables for any kind of defect before it is sent for dyeing.
A screen printing wooden table 18 m long (the longer the better) consists of a printing surface:a smooth table top or sheet of plywood with hinge clamps (gittis) attached. The ply surface iscovered with a jute fabric cover and a thick cloth to make the surface smooth. Below the ply is alayer of asbestos.
The boiler is connected through pipes, which run below the wooden tablebetween the asbestos sheet layer, and the printing surface. The heat produced by the boiler andtransferred through the pipes keeps the table warm, hence speeding up the drying process and alsoenhancing the color tones. Usually the heat provided is between 30-40 degrees C. It depends onthe kind of design: a dense design needs a higher temperature.
The screen consists of a frame of wood or metal, stretched with mesh (jaali)made of monofilament polyester nylon fibers. The mesh count is simply the number of threads perlinear inch that are woven into the mesh, and is usually determined by the type of ink to be usedfor printing. Generally a mesh count of 16/64 is used. Finer mesh will allow a thinner inkdeposit. This is a desirable effect when printing very fine detail and halftones. Typically afine mesh should be 200-260 threads per inch. Water based inks work best on finer mesh. These aregenerally used in graphic and industrial printing. Course mesh will give a heavier ink deposit.This type of screen is used for flatter, open shapes. Typically a course screen mesh will be160-180 threads per inch. These are generally used in textile printing.Wood frames have been replaced by metal because they do not warp with water. The most commonly used types of wood are cedar and pine. Pine is preferred because it is more water resistant while it is light-weight. Metal frames are made out of aluminum or steel. Aluminum is generally preferred because it is light-weight yet sturdy. There are some applications where steel is preferred such as in very large printing frames used for long printing runs.
Screens should be as big as possible. Smaller screens are less expensive, but they are very hard to use. The margin between each side of the design and the inside of the frame should be at least 1/3 of the image size. So for e.g. for a design of size 18 x 24-in., the inside dimension of the screen should be 30 x 40-in. 1/3 of 18 = 6, so the top and bottom margins must be 6 in. each; 1/3 of 24 = 8, so the left and right margins must be 8 in. each; 18 + 6 + 6 = 30; and 24 + 8 + 8 = 40. This is the minimum size.
A squeegee is a rubber blade gripped in a wooden or metal handle, which ispulled across the top of the screen. It pushes the ink through the mesh onto the surface of thecloth to be printed. Good squeegee blades print better and last longer. They come in variousdegrees of hardness. Medium hardness is the best. The longer the squeegee, the more difficult itis to print with, so it is always better to print with the squeegee running parallel to theshorter dimension of the screen. However, the squeegee should be at least 2 inches longer thanthe widest design to be printed.
The Process of Hand Screen Printing
The process of screen printing is of two main types:
All the steps involved in both ways of printing are the same except the treatment of the fabric after printing is done.
Delhi and Faridabad areas are known for pigment and discharge printing. The big mills in Ahmedabad use the rotary method of printing. Surat and Bombay regions use the pigment technique in abundance. The process of hand screen printing (discharge printing) has the following steps:
Art work/ Design
The artwork or designs to be printed are either provided by the agencies placing the order with the textile unit or are supplied by the printers themselves based on traditional designs found in the region. They may also be inspired by designs published in various books or magazines, the latest forecasts predicting the color stories and print /graphic directions or from an existing line. Once the artwork is ready, one needs to color-separate the design so that different screens can be made for each color.
Color separating a design from the original artwork means breaking down the design by color into a number of separate designs, from which screens/masters are made. The separations are printed over each other in layers, to create the original design. There are a number of ways to achieve color separations:
The most common technique used is the first one.
By Hand: Tracing the Design
This process is best performed using a lighted glass table, where light shines through the design, highlighting the areas to be copied. A separate tracing paper is used for each new layer/color separation such that each color is on its own piece of tracing sheet. When the sheets are superimposed on each other the original design is created. The ink used is opaque and completely black. The black areas of the tracing sheet are where the ink, of any color, will pass through the screen.Gray areas will give unpredictable results. Line thickness and fineness of detail are limited by the fabric to be printed on, screen mesh used, inks used, and other minor factors.
By Hand: Blocking the Design
By taking multiple copies of the original design, each separation is created by blocking out parts on each layer. This process is more accurate than tracing the design as each design is identical. However, blocking requires more thought and delicate separation, as complex designs (5 colours or more) can get confusing.
Transferring the Design Onto Screens
Step 1 Preparation
A metal frame of the size of the artwork is pulled out. Red lacquer is applied over the frame to prevent it from rusting over time. Then the mesh is stretched over the frame and nailed to hold it in position and red lacquer is applied again
Step 2 Cleaning the mesh
After the screen is stretched on the frame, there are still many dust particles adhered on the screen even though they are not visible to the naked eye. Hence the screen is washed with soap and left to dry.
Step 3 Mixing the screen emulsion
Photo screen emulsion is mixed with sensitizer (ammonium dichromate) before using. This is because they have a longer shelf life before they are combined. The ratio is 10:1 (e.g. in 1 kg emulsion put 10 g sensitizer). This is done in a dark environment. A thick coating of the emulsion is then applied on the screen and left to dry under the fan for almost an hour till it completely dries.
Step 4 Photo Stencil Exposure
A separate screen is made for each color in the artwork such that when all of them placed over each other would create the original design. Once the coating has dried, the positive film is placed on the camera table. Then the screen is placed in the exact position for a mirror image to be taken. The camera (lighted table) is switched on and the screen is exposed to the light for 1.25 minutes. The exposure time could vary depending on the design. The light does not pass through the black/opaque areas and the rest of the screen gets exposed. The exact design may not be visible completely till the emulsion is washed off.
Step 5 Screen Washout
The screen is taken to the washout stand and a jet of water is used to wash off the emulsion till the screen mesh is visible.
Step 6 The Final Touch Up
When the screen is dry, a final touch up is done using a brush and emulsion to avoid ink leak out during printing. Any pin-holes that are visible when looking at the screen with the light behind are also touched up. The four sides of the frame are then sealed using an adhesive tape, so as to provide extra protection.Ideally the screen should be used for printing after three days.
Step 7 Printing and Cleaning
After printing, if water based ink was used for printing, water can be used to clean the frame directly. However if the ink was oil based, it needs to be cleaned with solvent. Around 10,000 m of cloth can be printed using a screen. Over time the screen may deteriorate and need to be replaced.
Dyeing is an important part of the process of screen printing. It may be done on a small scale(where the artisans dye the fabric in small tubs), or in dyeing units (where the process is more or less automated). There are four main types of dyeing: Tub dyeing, Jigger dyeing, Winch dyeing and Jet dyeing.
The most commonly used technique is Jigger dyeing. Here the cloth is wrapped around the jigger flat and it keeps rolling out into the dye color bath. It can be a hand jigger or an automated power jigger. Dyeing is done according to the weight of the cloth. The color dilution is 2-3% i.e. if the fabric to be dyed weighs 10 kg, the water required would be 100 kg and the dye color mixed would be 2-3 kg.
Three main types of dyes are used:
Direct dyes are much easier to use and the dyeing process is faster. The color seepage is fast. However, the colors are not fast. Procion dyes have better color fastness, although the processing time is much longer.Both these dyes are used for plain solid dyeing of fabric only. Ramazol dyes have the best color fastness and these can be used for both plain dyeing as well as printing. They are more expensive than the other two and are locally purchased from Delhi. These are dry powder dyes. The dyed fabric is washed in a caustic soda bath to remove all the impurities in color before it is sent to the store room from where dyed fabric is issued for printing.
Setting up the Printing Table
Once all the supplies are assembled: the screens, the colors and the dyed fabric, the next step is to set the table for printing. The dyed fabric is laid on the table and stretched firmly using soft pins at close intervals. Then the hinge clamps or stoppers (‘gittis’ as they are called locally) are set.
The setting of the gittis requires skill. The screen for the first color to be printed is kept on the printing table. Three registration stops are marked on the surface of the printing table. These are such that there is one stop at each of the lower ends of the design to be printed, and one right in the center. The registration stops ensure that the placement of the screen is in exactly the same place each time relative to the image printed.
Strike Offs /Trial
Hand screen textile printing is as much a craft as a science. There are many variables that are beyond immediate control. To deliver printed fabric to the highest standards, a strike off needs to be printed before running production.
In the textile printing industry a strike off is defined as a small run of fabric printed with screens for the first time after the screens are made, or fabric which is printed in new colors or on new grounds with existing screens. The entire set of screens must be used, and there usually must be enough yardage to show at least three repeats. Strike offs serve a number of functions:
It is most valuable to check color matching, as there is almost always a slight shift between the color test and production conditions.
Two main reasons why a strike off is important before starting the production:
Hand Screen Printing
‘Screen printing is like ski jumping. Once you start, there’s no
convenient stopping place until the end.’
The process of hand screen printing involves two people at a time. The screen for the color that prints first is pulled out and positioned on the printing table, position set according to the gittis (stoppers). The first color is poured on to the screen and two people walk up and down the tables printing each color frame by frame, with the large squeegee pushing the desired color through the screen onto the fabric. Every alternate frame is printed. By the time the first round is over, the colours would have dried and the fabric would be ready for the second round of printing. This way, the process is repeated as many times as the number of colors to be printed.
After the cloth is printed and completely dried, it is put into the boiler and steamed so that the colors come out intense and dark. This process also makes the colors seep into the cloth ensuring a fine hand.
Finishing and Quality Control
After the desired color has been achieved, the fabric is washed. It is uring this time that the fabric might shrink by 8-10%. After it dries, it goes for quality check. The quality check is done for misprint or overlapping of design, bleeding of colours, large intervals between the screen shifts and color fastness.
Then the fabric is sent to the store-room where the yardage count is taken before it is issued to the stitching department where the equired fabric is cut and stitched into garments, bed covers, bed sheets, pillow covers and other requirements. The stitched product is then sent for final washing, drying, ironing and quality check before it is ready for sale.
Use of the Product
The hand screen printed fabric is used in a variety of purposes mainly for home furnishings and garments. Home furnishings include quilted products like quilts, pillow covers and cushion covers and non-quilted items like table covers, bed covers, bed skirts, runners, mats, napkins, cushion covers, pillow covers and curtain panels. Garment accessories like scarves, bandanas and sarongs are also quite in demand for the export markets.
Screen printed fabrics have good markets both in India and abroad. The main markets for this fabric are in the US, Germany and Hungary. Recently Japan has also shown interest in screen prints coming from India. There is a huge demand for screen printed fabric in the domestic market also.
Changes in Recent Years
By definition, a print is an image that has been produced by technical means, which enables it to be multiplied. The art of hand block printing and screen printing to produce attractive fabrics of rich colors and patterns is age old. With an ever increasing market for these printed textiles in oversees markets, newer designs and color combinations are being constantly experimented with. With new market directions, new technologies like rotary printing and ink-jet printing are emerging with fast growth and strong market penetration.