Screen printing is a stencil printing method. The printer pushes ink through open areas in a fabric mesh. Ink is either present or not on the paper so the appearance of nuanced gradations is difficult to achieve. This in itself adds both challenge and opportunity. The work around is based on graphic shapes as multiple dots or lines or as a "split fountain" method of blending colors as they are forced through the mesh opening.
The printing method is messy and challenging because so much can move around since fabric mesh stretches. Registration of colors is very difficult. It is best to design a print with these challenges in mind in order to make print production as forgiving as possible.