Screen Printing and Its History
Screen-printing, the technique that uses a woven mesh to support an ink-blocking stencil, which allows for the image of your choice on cloth, has been around for thousands of years. Although the technique itself has changed, the concept has not. Historians say screen-printing first appeared in a recognizable form in China during the Song Dynasty (960–1279 CE). Later, Japan and other Asian countries adopted this method of printing and advanced the craft using it in conjunction with block printing and paints. By the time Western Europe was introduced to the concept, it wasn’t until the late 1700s and even at that, it was not used as widely as in Asian countries. For the most part, screen-printing in England was used to print on wallpaper, linen or other fine fabrics. By the early 1910s, several printers began experimenting with photo-reactive chemicals using the well-known actinic light activated cross linking or hardening traits of potassium, sodium or ammonium bichromate chemicals with glues and gelatin compounds. Roy Beck, Charles Peter and Edward Owens studied and experimented with chromic acid salt sensitized emulsions for photo-reactive stencils. This trio of developers would prove to revolutionize the commercial screen-printing industry by introducing photo-imaged stencils to the industry. In 1928, Joseph Ulano founded the industry chemical supplier Ulano and created a method of applying a lacquer soluble stencil material to a removable base. This stencil material was cut into shapes; the print areas removed and the remaining material adhered to mesh to create a sharp edged screen stencil. Originally a profitable industrial technology, screen-printing was eventually adopted by artists as an expressive and conveniently repeatable medium for duplication. The Printer's National Environmental Assistance Center says, "Screen-printing is arguably the most versatile of all printing processes." So how does the screen-printing process work today? To start, a screen is made of a piece of porous, finely woven fabric called mesh stretched over a frame of aluminum or wood. This mesh is typically made of steel, nylon, or polyester. Areas of the screen are then blocked off with a non-permeable material to form a stencil, which is a negative of the image to be printed; that is; the open spaces are where the ink will appear. The screen is placed atop a substrate such as paper or fabric. Ink is placed on top of the screen, and a fill bar (also known as a floodbar) is used to fill the mesh openings with ink. The operator begins with the fill bar at the rear of the screen and behind a reservoir of ink. The operator lifts the screen to prevent contact with the substrate and then using a slight amount of downward force pulls the fill bar to the front of the screen. This effectively fills the mesh openings with ink and moves the ink reservoir to the front of the screen. The operator then uses a squeegee (rubber blade) to move the mesh down to the substrate and pushes the squeegee to the rear of the screen. The ink that is in the mesh opening is pumped or squeezed by capillary action to the substrate in a controlled and prescribed amount, i.e. the wet ink deposit is equal to the thickness of the mesh and or stencil. As the squeegee moves toward the rear of the screen the tension of the mesh pulls the mesh up away from the substrate (called snap-off) leaving the ink upon the substrate surface. Screen-printing has become popular for companies as a promotional tool as numerous types of apparel can be screen-printed with a company’s logo or name. Screen-printing’s versatility is also seen in the printing of products such as electronics, balloons and medical devices. There are few limitations when it comes to screen-printing and the industry is only growing bigger.