When a graphic designer needs to lay out a job of more than one color, it is necessary to create a color separation. In other words, if a client wants a job in three colors, there must be three pieces of artwork prepared. One layout is prepared for each color in the design. There are three specific methods for producing color separations. They are outlined below:
Mechanical Color Separation
The artist begins with a "base sheet". This is the first layout, and is computer generated or hand drawn. It may be a piece of paper or board. Then a clear sheet of plastic or acetate is taped on top of this base sheet. The top layers are called "overlays". Artwork is then pasted to these layers or drawn on these layers. This artwork lines up with the artwork below it, but the top layer will be used to create a plate for printing a different color. Certain masking films like Rubylith and Amberlith are used as overlays too. These films can fill larger areas to speed up production. Registration marks are attached to the base sheet and overlays to help a printer line up the artwork when the job is printed.
Computer Generated Spot Color Separation
The artist creates the artwork in a software program like Corel DRAW, but only uses "spot colors". "Pantone spot colors" are usually used. The software has the capability to electronically separate the colors and print them on separate sheets. It will print the registration marks on the sheets as well. This is the most widely used technology for producing simple spot color separations. It is excellent for simple business cards, letterheads, and silk screen designs.
Process Color Separation
There are four primary process colors. They are cyan (blue), magenta (red), yellow, and black. This process is the most common process used to print the color we see in magazines, comic books, and on shirt designs containing photographs. When these colors are used in combination, they can produce millions of colors. This is done by printing tints or percentages of colors next to or on top of each other. This cannot be accomplished without having the full color artwork scanned or it may be created in a special computer software program that supports this process. The major drawback to this type of color separation is that is very expensive to produce from start to finish. There must be four negatives produced, four plates made, and the paper must be run through the press up to four times. This process may also be used for screen printing. However, there must also be four positives produced, four screens made, and the shirt or printed product must be printed on the press up to four times.
There are certain vocabulary terms that the artist or designer must learn that relate to specific parts of a color separation mechanical. They are as follows:
base sheet - This is the paper or board onto which the inked design is created, or the art copy is pasted to.
cellophane tape - (also called "Scotch" tape) It is used as a "hinge" to attach an overlay.
masking tape - This tape is used to hold down the bottom of the overlay, so that it can be lifted off easily by the printer when the positives or negatives are produced on the camera.
overlay - This part of the color separation mechanical is usually a plastic sheet or special masking film that is taped onto the base sheet, over the original artwork.
register mark - (also called "registration mark" or "bullseye register mark") These are marks that are placed on each layer of a color separation. They must be lined up perfectly, to assist in lining up the colors when printing.
Review the illustration below, to learn which vocabulary terms correspond to the specific parts of a color separation mechanical.
Review the page again to be sure that you understand the material. REMEMBER, YOU WILL BE TESTED ON THIS MATERIAL!
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