Spot colors are special premixed inks used instead of, or in addition to, the process color (CMYK) inks. Each spot color requires its own plate on the press. (Because a varnish requires a separate plate, it is considered a spot color, too.)
If you are planning to print an image with spot colors, you need to create spot channels to store the colors. To export spot channels, save the file in DCS 2.0 format or PDF.
Note the following when working with spot colors:
For spot color graphics that have crisp edges and knock out the underlying image, consider creating the additional artwork in a page layout or illustration application.
To apply spot color as a tint throughout an image, convert the image to Duotone mode and apply the spot color to one of the duotone plates. You can use up to four spot colors, one per plate.
The names of the spot colors are printed on the separations.
Spot colors are overprinted on top of the fully composited image. Each spot color is printed in the order it appears in the Channels panel, with the topmost channel printing as the topmost spot color.
You cannot move spot colors above a default channel in the Channels panel except in Multichannel mode.
You cannot apply spot colors to individual layers.
Printing an image with a spot color channel to a composite color printer will print the spot color at an opacity indicated by the Solidity setting.
You can merge spot channels with color channels, splitting the spot color into its color channel components.
In the New Spot Channel dialog box, click the Color box. Then in the Color Picker, click Color Libraries to choose from a custom color system such as PANTONE or TOYO and choose a color. See Choose a spot color.
If you select a custom color, your print service provider can more easily provide the proper ink to reproduce the image.
This option lets you simulate on‑screen the density of the printed spot color. A value of 100% simulates an ink that completely covers the inks beneath (such as a metallic ink); 0% simulates a transparent ink that completely reveals the inks beneath (such as a clear varnish). You can also use this option to see where an otherwise transparent spot color (such as a varnish) will appear.
The Solidity and color choice options affect only on‑screen previews and composite prints. They have no effect on printed separations.
Use a painting or editing tool to paint in the image. Paint with black to add more spot color at 100% opacity; paint with gray to add spot color with lower opacity.
Unlike the Solidity option in the Spot Channel Options dialog box, the Opacity option in the painting or editing tool’s options determines the actual density of ink used in the printed output.
In RGB or CMYK color mode, you can remove spot channels and merge them into the standard color channels. When you merge spot channels in CMYK mode, the resulting colors usually don’t precisely match the original spot colors, because CMYK inks can’t produce the range of colors available from spot color inks.
The spot color is converted to and merged with the color channels. The spot channel is deleted from the panel.
Merging spot channels flattens layered images. The merged composite reflects the preview spot color information, including the Solidity settings. For example, a spot channel with a solidity of 50% will produce different merged results than the same channel with a solidity of 100%.
To prevent overlapping spot colors from either printing over or knocking out the underlying spot color, remove one of the spot colors where they overlap.
Use a printed sample of the overprinted inks to adjust your screen display to help you predict how colors will look when printed.
In some cases, such as when you use varnish and bump plates, you may want colors to overprint.
To create a trap when knocking out the underlying color, choose Select > Modify > Expand or Contract, depending on whether the overlapping spot color is darker or lighter than the spot color beneath it. In the Channels panel, select the underlying spot channel that contains the areas you want to knock out. Press Backspace (Windows) or Delete (Mac OS).
You can use this method to knock out areas from any channels under a spot color, such as the CMYK channels.