Silk Screen Printing Techniques

Silk-screen printing is a versatile printing technique that is easy to learn and use. It is ideal for printing on a variety of surfaces and materials, such as fabric, paper, wood, metal and plastic. There are several commonly used methods for creating silk-screen stencils, while the actual printing technique is the same regardless of how the stencil was produced. Silk-screen printing is commonly referred to as screen printing.

The most common and versatile method for making a silk-screen stencil is the photo emulsion method. For it, a wood frame is stretched taut with synthetic screen mesh, which is used rather than actual silk. The screen is cleaned with a de-greasing agent or soap and then dried. A thin coat of light-sensitive photo emulsion is spread on either side of the screen and any excess emulsion is scraped off. The coated screen must dry in a dark spot, away from light, such as a cabinet or cardboard box.

To prepare a design for use with the photo emulsion method, the design must be printed or drawn on a piece of clear vellum or acetate. Usually, a design is created on a computer in a software program such as Adobe Illustrator, Adobe Photoshop or Corel Draw, then it is printed on clear vellum. It is also possible to draw or paint with opaque ink directly on vellum or acetate. The resulting design imaged on the clear vellum or acetate is referred to as the film positive. It will be used to expose your silk screen that has been coated with photo emulsion.

Once the photo emulsion is dry, the silk screen is placed over a piece of foam rubber that fits inside the frame. The film positive is placed face down on top of the screen. A heavy piece of glass is placed over them. It is recommended to weight the corners of the glass with heavy objects such as books or paperweights to ensure close contact between the film positive and the silk screen. A bright light such as a halide work light is suspended over the silk screen and turned on. Consult the instructions for the emulsion to determine distance to hang the light over the screen and for exposure time. Turn off the light after exposing the screen and develop the screen with warm water at medium pressure. The emulsion will spray away in the image area, while the light will have hardened the remaining emulsion. Blot both sides of the exposed silk screen with newspaper and let it dry. The exposure time may have to be adjusted if the silk screen did not develop properly.

Once the silk-screen stencil has dried, it can be used to print. The screen is placed over the surface to be printed. Screen-printing ink is placed in the screen opposite the person printing. Holding a squeegee (usually a wood handle with a rubber blade) at a slight angle toward himself, the printer pulls the ink toward himself over the image area, applying pressure to the point of the angled squeegee that is in contact with the screen. Depending on the ink used and surface being printed, it may take more than one stroke to achieve complete coverage of the image. Different screen-printing inks are used for various materials, with specialty inks available for T-shirts, paper and glass, for example. It is important to have the proper solvent on hand for cleanup.

There are other methods for making silk-screen stencils. The most common is the drawing fluid method. This is an excellent method for children to use because it is less technical than the photo emulsion method. In this method, screen filler fluid, which most art supply stores carry, can be brushed directly on the silk-screen frame that has been stretched taut with synthetic screen. Once dry, the screen can be used to print. Any part of the screen left open will print, and so the printer must think in terms of negative space. Many artists prepare a design and tape it under the drawing to guide them as they brush on the screen filler fluid.