Screenprinting

The principle of screenprinting is somewhat different from that of other printmaking processes in that the print is taken not by the direct impression of one surface upon another, but by printing through an intermediary surface - the screen mesh. The images of screenprints are formed by various kinds of stenciling techniques, based on blocking out areas of the mesh either with sheet materials such as paper or stencil film or with liquids that fill the mesh. As well as being a fine-art process, screenprinting has a direct association with commercial and industrial printing processes, being used extensively in graphic, ceramic, and textile design. It is a colorful, versatile medium which you can adapt to the context of your work.

Filling the screen

Squeegee at an angle

History of Screen printing

Screenprinting is quite a modern method of printing compared to many other types of fabric decoration. It was first used at the beginning of the 20th century in England. This may seem a long time ago but compared to block printing, hand painting, tie-dye, batik, woven and stitched designs, wooden rollers and engraved metal rollers, this is really very new.Asia and the Middle East were the areas to begin printing patterns onto textiles. Block printing began in India as long ago as 3000 years before the birth of Christ (B.C.). The Japanese who had used many methods of fabric decoration adapted from the Chinese were probably one of the first to use a stencil technique which later had much similarity to modern stencils used in screen printing. They used rice paper which had been cut to form patterns and this was held together with human hair. The paper would resist the colour and the hair would be fine enough to allow the colour to flow past onto the fabric. The first screen printing was developed in England around 1900 but it was not used in factories for another 30 years. Screen frames were made of light wood and covered with a pure silk gauze.  It really took off after WWI as an industrial process and became a popular art form in the 30s and the decades following. Andy Warhol and the pop art movement made extensive use of the medium.Now stronger synthetic gauze is used, and metal frames, which will not twist or warp like wood. One of the newest types of screens is a cylindrical rotary screen make of very fine metal gauze which allows fabrics to be printed on a moving conveyor belt.

Tools and materials

There is not much equipment required for screenprinting. It consists of a screen - a wooden or metalic frame with a fine-mesh fabric stretched over it - and the squeegee. This is a rubber blade set in a handle, with which the screen ink is pulled across the mesh. The mesh transmits an even coating of ink which adheres to the paper below the screen. The stencil, whatever its form, seals certain areas of the screen so that the ink cannot pass through, thus creating positive and negative color areas. The stencil can be a material as simple as thin paper that will adhere to the underside of the mesh - for example, newsprint, tracing paper, or greaseproof paper. Commercial stencil film is a gelatinous material on a plastic backing that can be cut with a sharp craft knife - when soaked with water it softens and is pressed into the mesh before the backing is removed. A similar effect can he obtained with self-adhesive plastic film applied to the screen, and you can also use adhesive tapes.

Screenprinting using a paper stencil

Use light weight paper. It is even possible to use tissue paper or newspaper. A paper called M.G. Litho is very good. Try and get sheets of paper that are a little longer than the screen.

(a) Try cutting out any shapes with a sharp knife (stencil or cutting knife). Make the shapes very simple and make several stencils.

(b) Tape a piece of fabric or, if you're just practicing, even a large piece of plain paper onto your printing surface.

(c) Place the stencil (do not tape) with the design area on the material to be printed.

(d) Place the screen flat down on the stencil so that the edges of the stencil paper are evenly covered. Make sure the inside screen printing area of the screen is not smaller than the shape to be printed.

(e) Put the squeegee into the well and at the end closest to you. Hold the squeegee to make a narrow channel with the screen side and then pour a large amount of colour into the channel. (Diagram 2).

(f) Hold the screen edge with one hand and the squeegee in the other hand, or get someone to hold the screen while you work the squeegee. Lift the squeegee in an angle (Diagram 3) and move it in an even motion to the other side of the screen. Gently wipe the colour off with the front edge of the squeegee blade onto the screen frame then slide the squeegee behind the dye and firmly move the colour back over the screen. Wipe the excess colour off on the edge of the frame and rest the squeegee to one side. Lift the screen gently from one side then lift off the fabric. You will probably find that the paper stencil will stick to the underside of the screen. If you wish to you can place the screen in a new position and repeat the printing process again OR take off that stencil and try one of the others. If you plan to have a rest and you don't want to cover a new screen again, scrape out all the colour that is left over, put it back into the storage jar and wash the screen out with water immediately. If possible wash it outside using a strong spray garden hose near a gully trap or drain.

If you are printing onto paper you only need to give one even stroke with the squeegee. Painting on fine cotton - two even strokes. Painting on heavy cotton , canvas or hessian  - three or more strokes.

Try some of these variations with your open screen.Put strips of cellotape across your screen, or tear strips of paper and lie them on the fabric to be printed.

Fold a piece of paper in half and in half again and then cut out various shapes with a pair of scissors.

Put the screen flat down on a hard clean surface and then draw with a candle or crayon onto the mesh. Press hard so that the wax will clog the mesh. This will give textured lines when printed. This wax can be removed after the screen has been washed, by ironing gently onto newspaper.

Screen printing using film

Screen printing begins by creating the art work, which is comprised of a piece of clear film (transparency copy?) that has the image to be printed in black. The screen is created by stretching thin but durable fabric over a wood or metal frame. The fabric is then coated with a light sensitive emulsion. The film is taped to the screen and exposed to a bright light. The dark areas of the film block the light from hitting the areas of the screen that are to print, and the transparent areas allow a photo-chemical reaction to harden the emulsion. When the screen is rinsed with water the emulsion washes out of the areas that are intended to print. The screen is then clamped into a frame that holds it steady while printing. Ink is forced through the fabric by the use of a rubber bar, called a "squeegee", that is pulled across the stencil, and the shirt is held in place by adhering it to a flat board with spray adhesive. Once the inks have been applied the shirt is placed on a conveyor belt that cycles it through a dryer. The dryer fuses the components of the ink together, causing it to become "cured" and durable. Then you put it on and scream really loud because it is still about 900 degrees.

For more information

Photo emulsion

is a photosensitive substance used in screen printing that hardens when subjected to ultraviolet light. To prepare a screen for printing, it is coated with liquid photo emulsion and allowed to dry. Opaque, monochromatic artwork (known as a stencil) is transferred onto a transparent medium such as glass or film or transparency which is placed over the emulsed screen. Ultraviolet light is shone on the screen causing the emulsion to become hard and insoluble, except in areas that are covered by the opaque artwork. The entire screen is then washed in water or solvent, allowing any emulsion not hardened by the light to rinse away, leaving a representation of the artwork on the screen. Most commercial photo emulsion products consist of either bichromated gelatin or a photopolymer such as bichromated polyvinyl alcohol (PVA) in suspension. It is often light brown in color and has the consistency of heavy syrup. Most brands/types of emulsion have a short shelf life (on the order of days or months) and must be refrigerated. After being used for screenprinting, the emulsion may be stripped from the screen using chemicals known in the industry as reclaimer, usually one or a number of extremely toxic solvents.

What is a print – excellent flash animation from moma