Most images consist of solid shapes of color, or Spot Colors. These images generally print well on lower mesh count screens and are usually vector based artwork.
Some images, though only made up of a few colors, have different shades, fades or blends of color. These are what we consider halftones. Halftone Imprinting is achieved by printing groups of dots or "halftones" instead of solid shapes. These halftones require a higher mesh count screen to hold the dot pattern. To get our halftone screens we have to "index" the image to pull the main colors out. Most profesional mass production work is created using indexed color with usually 8 to 18 colors. The benefit of Index Color Separations is there is no color blending and your image comes out the same every time. Currently we are capable of up to 6 colors.
When more than 6 colors are required to produce an image we are left with Process Color Separations. Process Color utilizes Cyan, Magenta, Yellow, & Black to blend and create the full spectrum of color. Though Process Colors sound nice they tend to be unpredictable. Since the colors are mixing on the shirt, and the rule that perfection is impossible, the colors are not garunteed to mix the same on every shirt. We have had good results with our process imprinting, but the consumer should be aware that there may be color shifts from shirt to shirt. Process Colors require higher mesh count screens. Since there are only 4 colors creating the full spectrum of color we are left with room for two additional spot colors or white plates.
White Plates are usefull when printing on dark garments. Most inks are transparent and to print on dark you first have to cover it with white. Some Spot & Index Color projects have substituted white ink for light gray or khaki. It all really depends on the artwork and the intended look of the garment as to which color base to use. One Color Images on dark garments in bright colors like red, orange, yellow, & light blues require a white base unless the inteded look is to be transparent heathered ink. Process separations on dark always use a white base plate and usually a second white for any white that actually shows thru the image. White ink is generally thicker since it covers and requires a lower mesh count screen. We have done white plates on higher mesh count screens to achieve halftones in our highlight white, but rarely for base plates.