To print a design on a t-shirt using the screen printing method, each ink color in the design is printed through it's own screen. Here are some explanations on how to determine how many colors your design may have.
The most basic printing, of course, is the simple one color on a white shirt. Not much to explain here. It's one ink color.
This is a two color. The white in the middle does NOT count as an ink color, because the shirt, itself, is white.
Again, the white in this image does NOT count as an ink color.
Even though this image may appear to be just 3 colors (black, green and red), the red on the car is a lighter shade of red than the outer circle. There are two ways to achieve this. One was is to make a 4th screen with a lighter red ink. This method will produce the smoothest look, but will, of course, cost more.
The second method for dealing with shades of color is with the use of halftones. These are small dots of the original color (the red of the outer ring in our example) in various sizes and spacing to create the illusion of a different shade. This is how they often will print newspaper images. The plus for this method is that you don't have to pay for an additional color. This method works best on photographs or larger areas with varying shades of the color rather than large solid areas or tiny images - like text.
On light colored shirts, (such as yellows, greys, pinks, light blues, etc.) the colors can go directly onto the shirt without the need for an underbase (more on that later).
As with the white shirt above, the green color in the design on this example does NOT count as an ink color. Unless, of course, you need to have that green be a different shade of the color than the shirt's color.
Dark shirts (such as red, blue, green) can be printed with one color without the use of an underbase - as long as that color is DARKER than the shirt itself.
To achieve the bright green in this example, the use of an underbase may be required. What this means is that we will first print a thin layer of white ink. We then print the green on top of that. This gives a bright backing so the green stays true to it's color. Without the underbase, the green will look very dark as the red shirt color will leach through. Think of the underbase as a paint primer. This example would require 3 screens (underbase, green, black).
Again, to achieve something like this bright red on a black shirt, an underbase would be required. This would be considered a 2 color job (underbase, red).
In this image, we would require 3 screens. Because the white underbase is such a thin layer, it alone does not produce a bright enough white to achieve the brightness of white desired. An additional white screen would be necessary to go over the white underbase. So this shirt would be 3 screens: white underbase, red, white.
We hope this helps explain better how ink colors in screen printing work. If you have further questions, please don't hesitate to send us your image and we can determine the count exactly.