Just a sample from the previous design. This time it's of the shading.
One the left is the original. That on the right is the result after adjusting it for Screen Printing.

Why?
Because the printers that create the screens can only see pure black and not shades. To counter this, the artist must use a program (or do it by hand) like Photoshop to convert the shades to Grayscale to remove all color. Then he/she must set it to Bitmap. Bitmap does not support transparency so the program (Photoshop in this case) allows the artist to choose a preset shape to replace the transparency. In this case I used "round/circle". The program then adjust the number of Rounds to match the look of the previous transparency. But because it's a Bitmap now, the artist needs to remove the white from the image. To do this I converted back to Grayscale and then to RGB. I then use the Photoshop Filter PlugIn called "Eraser Genuine" and tell it to remove all the White. Then I'm done with the shadows. ^_^

Click here for the LARGE version if you'll like to see the details.
http://fc03.deviantart.net/fs71/f/2013/079/8/e/1canonfodernomore_shadessamples_by_sespider-d5ypjfv.jpg

Sorry about the watermark.