What is Screen Printing

Screen printing, serigraphy, or silk screening is considered one of the earliest methods of printing, which involves passing ink, or any other printing substance, through a screen or mesh, stretched on a frame, and on which a stencil has been applied. The image that is printed is determined by the openings of the stencil.

History of Screen Printing

The screen printing technique was first used by the Chinese almost 2000 years back. They stretched human hair across a frame made of wood in order to form the screen. And on that, they applied a stencil created from leaves, which were stuck together to form different shapes.

Later, the Japanese adopted the process, although they made the mesh out of woven silk and used lacquers to create the stencils. This is the reason why screen printing is also known as silk screen printing or silk screening.

However, other materials apart from silk for screen printing also have a long history, with the ancient art of stenciling be used by the Greeks and Egyptians as long back as 2500 B.C. The word ‘serigraphy’, in fact, has been derived from the Latin word for silk, ‘seri’, and the Greek word for writing or drawing, ‘graphein’.

It was in 1907 that screen printing as an industrial process was first patented by Samuel Simon near Manchester. A few years later, around the time of the First World War, the Selectasine method was developed by John Pilsworth of San Francisco. This method basically introduced the process of using the same screen to create multi-color printing. It became very popular because large quantities of posters and signs could be printed. The technique was also adopted by American graphic artists to create their artworks.

Today, screen printing is popular both in commercial printing and fine arts, and is used to print images on CD covers, T-shirts, glass, ceramics, wood, metals, paper, polypropylene, polyethylene, silk and cotton fabrics, posters, flyers, signs, and even on watch dials.

Screen Printing Technique

Screen printing technique basically involves three elements – the screen, which will carry the image; the squeegee; and the ink. As was the method used in the past, a porous mesh is stretched tightly over a wooden or metallic frame. It is essential for the tension to be right so that the color gets registered accurately. The mesh used is a stainless steel mesh, a porous fabric, or a polymer mesh. The stencil is created on the screen either photochemically or manually. The stencil is what creates the image that is printed, and in other methods of printing it would be denoted as the image plate.

The ink is applied on the substrate by the screen being placed on top of the material. A paint-like consistency of ink is then applied on the surface of the screen. Then the squeegee is drawn across the screen to force the ink through the openings of the fine mesh. The ink passes through only those areas where there is no stencil, thus forming the image on the printing material. The thread count and the diameter of the threads determine the amount of ink deposited on the material.

Many elements like the form, size, composition, angle, speed and pressure of the squeegee determine the quality of the image produced. In the past, the blades of the squeegee were made of rubber, which was susceptible to wear, the edge being prone to getting nicked, and thus had a tendency to distort and warp. Although rubber blades, such as neoprene, continue to be used, these days squeegee blades are usually made of polyurethane, which can be used to make as many as 25,000 impressions, without any significant deterioration of the image.

Once the item has been printed, either by automatic or manual screen press, it is then placed on a conveyor belt, which takes it through a UV curing system or a drying oven. Rotary screen presses pass the material through the curing or drying process automatically. Although rare, but certain inks are still air dried sometimes.

Innovations in Screen Printing

While in the past the rate at which the ink dried determined the rate of production, modern innovations and improvements have increased the production rate greatly today. Some of the innovations that have been incorporated, which have resulted in improving the production rate and have also led to the popularization of screen printing are:

• The introduction of automatic presses, which have largely replaced hand operated presses.
• Improvement in the method of drying, which has increased the production rate significantly.
• The introduction of UV curing ink technology.
• The development of rotary screen presses, which allows the press to be operated continuously.

From using meshes made of hair, to silk, to polymer, screen printing technology has come a long way indeed. Although the basic technique of screen printing has remained the same, but with the advent of computers and electronics and other new innovations, Samuel Simon, who patented it, would barely recognize it if he were around today.