Creating Standards for Underbase Printing
Minimize mistakes by creating shop-wide best practices.
Continued from Establishing Rule for Underbase Printing.
Once you have tested your current equipment and processes, find a design to run using those settings and see how your results compare. The goal is to find a good base level for an underbase: settings you can fall back on when things get complicated.
A simple but effective test print consists of grids of halftone dots from 0 to 100, showing what different densities of an overprint color will look like on different densities of underbase (see Figure 6). Set up this test print for different colors and run it making no changes from your usual production processes. You’re trying to determine the minimum effective underbase, or how much white ink is needed to make the final color appear bright, using as little as possible so that the print won't feel heavy.
You can also use such a test to find best practices for specific press settings. Take squeegee pressure, for example. Set up the test screens so that the print is done with minimal squeegee flex (to help avoid screen stretch), setting up the squeegee at a more vertical angle. Increase the flood pressure so that the ink is pushed just slightly into the ink well on the print side of the screen, without blanketing it. Reduce the squeegee pressure until the ink doesn't release from the screen all the way, and then slowly ramp the pressure back up again until you find the minimum amount necessary to consistently release the ink from the stencil onto the shirt. At the end, you'll have standard floodbar and squeegee pressure settings that will help minimize the thickness of the underbase.
Just remember that the test is dependent on the color of the garment or surface you use. In other words, it may not work the same if you do the test on a black shirt and then try to print a royal blue garment with the same settings. The base color of the garment may make the underbase and top colors look different, especially if the underbase isn't totally solid.
The finest print on a dark shirt will only be as good as the underbase that creates the foundation on which the other colors are built. Spending some extra time to master underbase printing will pay big rewards in the quality of your dark garment prints, and it will make other types of printing seem easier as well.
See also: Design Tips for Creating an Underbase.