Most screen printing ink is slightly transparent. When a colored ink is printed on a dark shirt color, the shirt dye and fibers tint the ink so the print appears dark and dingy. To keep colors bright, we first print a layer of white ink and then print the colored ink on top of the white. This layer of white is called an underbase. Even if no white ink is showing in your design it’s still there. Kind of like that guy bustin’ those awesome dance moves in a mascot costume. No guy. No spirit.