Screen Printing Stencil Techniques
Screen printing is all the rage in the printmaking and graphic design world as it is a quick an efficient way to reproduce ones work on a variety of surfaces from posters to clothing to other types of unconventional material. There are different methods, however, in which to create the stenciled image on the mesh screen, each having its own advantages in specific printing circumstances.
Screen filler is a blocking agent that when dry prevents ink from passing through the mesh screen. This substance needs to only be applied in thin coats and has a quick dry time, after which it becomes hard and solid. Screen filler works as a wonderful touch up agent when holes or eroded spots are found in photo emulsion, but when left dry can also leave unwanted blocked spots. It is also applied over dried drawing fluid to form the negative portions of the images for which the drawing fluid is the positive. It is a very easy substance to use that can be brushed or squeegeed onto the screen. Oil cleaning products are most often used to get dry screen filler out of the screen, but the efficient way to clean the screen in to spray it with Grease Lightning, let it soak until all the suds are gone, and then wash it out with a pressure washer.
Drawing fluid is used for a positive screen printing technique and is very easy to clean. This thick, blue liquid is brushed onto the portion of the screen through which one wants the ink to pass. When dry and hard to the touch, screen filler is squeegeed over the mesh and drawing fluid. Once the screen filler is dry, the drawing fluid can simply be washed out with water leaving open mesh and screen filler, thus, forming the stencil. This technique is great for those doing reductive printing of a simple image as the screen filler when used this way does not need to be cleaned off with each new color.
Photo emulsion by far creates the most detailed screen prints out of all the stenciling techniques. It is a light sensitive agent that becomes hard when exposed to light. The emulsion is applied to the screen in a dark room in a thin and even layer. After the emulsion dries, a transparent film that has the opaque portions of the desired image is placed backwards onto the back side of the screen (the side in which the mesh is at the same level as the frame) and it is held down by a clean plate of glass. The screen with the film and glass is exposed to light, which depending on the type of photo emulsion used requires a certain wattage and exposure time. This is most often done with a full size exposure unit, but hanging three or four light bulbs is also feasible for those on a low budget. After the recommended exposure time, the screen is then rinsed with the portion of the emulsion exposed to light hardened and the portion covered by the opaque areas of the film washed out, leaving behind a stencil. Once prints are complete, the emulsion can be cleaned off by soaking the screen in bleach or using emulsion removal products. This technique is the most frequently used compared to others due to its efficiency and the detail it can achieve, especially with thin lines, text and half tones.
Different manufacturers sell them in different varieties, but these films are first cut and then applied to the mesh screen to make the stencil. Using and X-Acto knife, the film is cut to form the desired positives and negatives of an image and is then adhered to the screen. Depending on the brand and type of film, some can be adhered to the screen sing water while others require adhering liquid or have adhesive built in on the other side of the film. The type of film also dictates the types of ink that can be applied and the types of solvents that can be used to remove it. For instance, film that adheres with water cannot be used with water soluble inks. The advantages of this relatively new stenciling technique are its durability under the press and how little it is affected by temperature.