Painted edges on flat pieces
Yes, a postcard can have a painted edge — from a single sheet to a heavy duplex construction.
Edge paint is applied by hand: the trimmed stack goes into a vise and the colour is worked into the exposed edge, then left to cure. It is slow, and that is why it suits a considered run rather than a mass mailing.
Because the vise turns the whole stack into one paintable surface, even a thin single-ply sheet can be edge painted. A duplex or heavy cotton simply gives each finished piece a broader, more visible line.
Any colour can be matched, including to a foil or to the face ink.
Below roughly a heavy cover weight there is no edge to paint. This finish needs thickness before it needs anything else.
Looking for cards rather than flat pieces? Painted edge business cards.
Painted edges — questions we get
Can I get a painted edge on a postcard?
Yes, on duplex or heavy cotton. The edge has to be thick enough to hold paint, so this is a heavyweight build rather than something you add to a standard sheet.
Does edge paint survive the mail?
It cures hard, but it is still a painted surface. In an envelope it arrives perfectly; loose in the mail stream it will pick up marks along with everything else.