Overprint
What Is Overprint in Printing?
Overprint means printing one ink directly on top of another, so the two mix where they overlap. The opposite is a knockout, where the top object cuts a hole in the inks beneath it and prints on bare paper.
Knockout is the default in design software and in PostScript, so overprint is usually switched on object by object. Printers use overprint mostly for small black text and for finishes such as spot varnish and foil. In CE.SDK, designs also export as knockouts, and spot-color layers can be set to overprint in the PDF.
Overprint vs. Knockout: What’s the Difference?
The choice decides what happens to the ink under an object, and what the press does when its plates are slightly out of line.
When the black plate drifts a little, as it can on press, knocked-out text shows white paper beside each letter. Overprinted text has the background ink underneath, so no gap appears.
| Overprint | Knockout | |
|---|---|---|
| Ink underneath | Stays and prints | Removed under the object |
| Top color | Mixes with the ink below | Prints as set |
| If plates shift | No gap appears | A thin white gap can show |
| Default | Switched on per object | Yes, in most design tools |
When Should You Overprint?
Overprint small dark elements, so a plate shift can’t open a white sliver beside them, and finish layers that must sit on top of the artwork. Keep the rest as knockouts: white disappears when it overprints, and large black or light areas mix with the inks beneath.
Set to overprint
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Small black text and fine lines on color
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Spot varnish, spot UV, and foil layers
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Two spot inks layered to make a third color
Keep as knockout
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Anything white
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Large black areas over photos
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Light colors over dark ones
How to Use Overprint in CE.SDK
Start from knockouts
Every object knocks out by default, so a fill replaces the inks beneath it in the exported PDF. That’s the right setting for most of a design.
Set finish layers to overprint
Give a varnish or foil layer its own spot color, then set that block to overprint. Fill and stroke overprint are documented on every platform, and the PDF writer honors them only for spot colors, the inks that print from their own plate.
Export to PDF
The overprint flag only affects PDF export, so the design looks the same on the editor canvas either way. Since v1.74, overprint set on text is also kept in the exported PDF.
Check it with overprint preview
Open the exported PDF in a viewer with overprint preview turned on. A finish layer should sit on top of the art, and nothing white should be set to overprint.
Overprint for Varnish on Labels and Storefront Finishes
Spot varnish on product labels
A label template carries a spot varnish layer named for the press. It overprints the artwork, so the varnish lands on top of the design rather than replacing it.
Foil in a print storefront
A business card template sets its foil shape as an overprinting spot color. Customers change the text and colors, and the foil still prints as its own layer over their design.
FAQs
It was most likely set to overprint. An overprinting object doesn't knock out what's under it, and white puts down no ink of its own, so the color underneath fills the space and the white vanishes. Set white objects to knock out instead.
Trapping is a small overlap between two touching colors, so a slight shift between plates leaves a thin mixed edge instead of a white gap. The overlap is usually a thin spread of one color set to overprint, which makes trapping one use of overprint.
Only with overprint preview turned on, in your design tool or PDF viewer. Without it, an overprinting object usually looks just like a knockout, so a wrong setting stays hidden until the job prints.
Links
Documentation and references for this concept.
Related Terms
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