Capillary film is perfectly smooth, so it’s easy to create a precisely detailed stencil. Capillary film comes in different thicknesses, or emulsion over mesh (EOM), so you know that your stencils are always the right thickness for your print job. While some printers claim that films create less durable stencils because the emulsion is only applied to one side of the screen, capillary film manufacturers report that stencils made with their products can last for tens of thousands press runs. The biggest downside is that capillary film is more expensive than liquid emulsion; the film proponents often cite the time saved as making the film well worth the cost.
Capillary film most often comes in rolls that you cut down to fit your screens, or you can purchase precut sheets to make coating your screens faster and easier. You’ll want to be sure that you’re using film that’s compatible with the mesh count you plan to use for your print job, as well as with your ink. The film is incredibly easy to apply to screens, following a few quick steps.
You probably know that every good stencil begins with a clean screen, but a well-cleaned screen is even more important when you’re applying capillary film. Any grease, stains or dirt on your mesh will interfere with the film’s adhesion. First, thoroughly clean your screen with a degreasing agent, and rinse thoroughly. If there are stains on the mesh, also use the necessary agents to completely remove them.
Your screen needs to be completely flooded with water to allow the film to fully adhere. Some printers advise scrubbing the screen to help the water to remain on the screen, but this can damage your mesh. Instead, consider using a wetting agent designed specifically to help with capillary film adhesion.
This part of the process is fairly straightforward. Apply water to the surface of the screen, with the goal of getting as much water as possible to fill the individual squares of the mesh. If you applied a wetting agent, your water should cling to the mesh with no problem. If you skipped the wetting agent, you will need to pour the water downward over the screen so the surface tension of the water will cause it to suspend between the openings in the screen.
The easiest way to apply the capillary film is to begin with your film tightly rolled, with the emulsion side out. Apply the top edge of the film to the screen, pressing slightly. Applying slight pressure as you go, unroll the film down the screen. You will feel the film pulling out of your hands as it bonds to the water.
To ensure a complete bond, you’ll need to be sure that all of the emulsion has come into contact with the water. The best way to do this is with a window squeegee – a printing squeegee may be too firm for the job. Flip the screen over, and gently run your window squeegee around the back of the film.
Your screen will need to dry for about 20-30 minutes to be sure that the emulsion is ready to be exposed. Dry the screen horizontally, just as you would with a screen coated in liquid emulsion. One of the easiest ways to tell that your emulsion is completely dry is by removing the polyester film: If the emulsion is dry, the film will peel right off with very little resistance and little to no noise.
Once your screen has dried completely, you are ready to apply your film positive and expose your screen. This part of the process will be the same as working with a liquid emulsion. Follow the manufacturer’s instructions for exposure times, and wash out the stencil from the emulsion side so you don’t risk breaking the bond between the emulsion and the screen. Once you’ve washed out your screen, you’re ready to follow your normal printing procedures with your capillary film stencil.
Looking for more tips on choosing and using screen printing emulsion to create quality stencils? Check out these blog posts: