Understanding Screen Printing
Screen printing is a process in which a stencil is placed over a piece of film, positioned on the fabric that will eventually become the finished article. In general, it's done by large machines with hoppers and rollers rather than individual screens.
The process begins by coating the stencil with ink to create an area where subsequent colors will be printed. Next, the screen itself is spread out and placed over the wet ink-coated area—the screen has evenly spaced holes through which ink can pass as it travels through to reach printable areas of the fabric underneath. After allowing time for compound to dry, heat caused by friction helps set the dye in those areas where color has been deposited.
Types of screens, as well as methods for applying them to different sizes and shapes of material, have become relatively standardized through the years. Early stencils were made of metal. Modern ones are often made from plastic or glass. The more recent addition of adhesive allows them to be applied directly over a substrate, such as fabric.
Modern developments in the process have extended the possibilities for screen printing into areas not previously accessible to it—particularly where color can be combined with a number of black-and-white images and printed onto paper and other various surfaces where traditional photographs could not be taken.
There are essentially three types of screens that can be used in modern screen printing:
Ink-Jet . This is what you're likely to find in most commercial printers. It's a specially constructed stencil, typically with rollers attached, that holds a screen and squeezes the ink onto it by way of pressure exerted on the screen itself. When the roller is turned off, the screen squeezes out excess ink from gaps between its teeth.
The concept is similar to that of an ordinary squeegee or paint roller—except it's made for use with an ink jet printer instead of paint or glue.
Electrostatic . Compared to ink-jet, this is relatively new technology that allows the stencil to be placed on a piece of paper and then pressed against it. The ink in the screen can be printed directly onto the substrate, or the screen itself can be covered with an opaque coating and pressed away from it.
Braille screen printing . This is another relatively new process that prints braille characters directly onto paper through a process using a side-to-side contact between a stencil, called a "braille plate," and paper (in much the same way as hand writing!). This was done by applying ink to both sides of blank pieces of paper, laying them on top of one another and then pressing them together. It has been adapted for use as a type of computer printer.
It works by embossing letters into paper through the use of a "braille plate," rather than through pressure applied by hand. The plate—usually made of plastic or glass—has each letter engraved into it, one at a time. It works in much the same way as the keyboard on a typewriter, except that each hole and bump isn't raised just slightly but enough to make contact with the paper underneath.
The process is similar to that used by manual printing devices and traditional stencil printing, though it's using an electronic process instead of manual ones.
Some of the most interesting, and likely to prove valuable in the future, developments in screen printing have been in color graphics printing. The process creates an excellent way to print full color images onto fabric and other surfaces.
The process begins by applying a stencil with a specially prepared ink to it. Next, the screen is placed over a piece of film that has been coated with ink, so when both are pressed together, the screen can transfer ink from one medium to another through a small number of progressively smaller holes. If necessary, pressure can be applied by means of rollers and squeegees via a machine.
Color printing is done by printing the screen and stencil onto a single piece of film, which is moved back and forth between a roller and squeegee, so that each area has the same amount of ink applied as it needs.
There are many other methods of decorating fabrics using screen printing, some more common than others to regional industrial arts scenes. It has been adapted for use in many areas where stencil is not practical— notably in areas of high security and military design, such as camouflage patterns, where a large number of screens would be necessary to cover an area with multiple images.
Screen Printing has been used for various ceremonial purposes throughout history. The ancient Egyptians used screen printing to create mummy masks and other body decorations. The Greeks and Romans also used it for the same purposes. There are also many examples of royalty using its unique creative abilities for decorative purposes, including King Louis XIV of France, who had a mural painted at Versailles depicting his favorite hunt— the four-legged stag—and his hunting dogs.
In medieval times, it was believed that certain pictures were invisibly present in wax (hence the term 'wax seal') when applied to documents or metal containers (such as wine amphoras) by the use of a special wax-based adhesive called colophonium , which was made from beeswax mixed with oil or animal fats. The term "coulommiers" is used for this type of tool in France, and was first introduced as a printing process at the end of the sixteenth century.
Early printers found that using colophonium to print text or images directly onto paper was too expensive, so they began using a new technique called stencil printing. The stencils consisted of an engraved copper plate on which an image could be drawn and then covered with wax or shellac. By placing a piece of colored paper over it and pressing them together, the image would transfer onto the paper. The result was sometimes used to embellish documents at a much lower cost than if they had been printed using colophonium ink.
It's still possible to have modern day paper documents or souvenirs printed with colophonium ink at many museums in France, including the Louvre and Musée d'Orsay in Paris.
In the sixteenth century, printers began using a new form of stencil printing called "coulommiers". The process required specially prepared printing plates made from copper and a wax-based stencil that was attached to a curved wooden handle. The plate was pressed into paper with such force that the design on it was transferred onto the paper. (A piece of colored paper was then placed over it and pressed together to transfer the image.
Conclusion
Today, stencil printing is still a popular form of expression and commercial design. The term "stencil" can be used to describe the process, the product (a printed image transferred onto paper or fabric), or a type of artistic movement—with so many different applications, it's no wonder it has been around since before the dawn of human civilization! It's also easy to see that stencils have been adapted and changed to meet our increasingly sophisticated needs. The next time you see a rock band's concert tee shirt or your favorite artist's poster in your local hot spot, ask yourself what is really being expressed by the use of stencils.