Why does color bleeding occur on porous materials?
Porous paper or uncoated material draws the ink of the previous color into the paper. When the next color is overprinted, the two colors bleed into each other at the boundary. This is not Misregistration: Misregistration shows a line of exposed paper white or a hard edge, whereas color bleeding is two colors mixing into a muddy color along the same boundary. First reduce the ink layer and thicken the ink; do not rely on increasing pressure to “press it in.”
Porous or uncoated materials can pull the ink of the previous color into the paper, and when the next color is printed over it, the two colors bleed into each other at the boundary. This is not Misregistration: with Misregistration you can see a line of paper white or a hard edge, while ink bleeding is the two colors mixing into a dirty color within the same boundary. First reduce the ink film and make the ink thicker, do not rely on increasing pressure to "press it tight."
What the paper is doing
Uncoated paper, gray-backed whiteboard, and some very absorbent label papers do not have a coating layer on the surface to hold the ink up. The binder of the first color carries the pigment along the fibers, and when the second color is printed over it, the two pigments meet within the fibers, and the boundary becomes dirty. When you magnify the boundary, you do not see a clean line of paper white, only a brown or grayish transition.
The boundary of Misregistration is clear: either the paper is exposed, or one color is printed outside the other, and the edge is still sharp. These two cannot be fixed with the same set of registration corrections. If you adjust registration when there is ink bleeding, the dirty color is still there, only the location of the dirt moves.
How to read the boundary
| Boundary | Name | Do first |
|---|---|---|
| Two colors mix into one dirty color | ink bleeding | Reduce the first color's ink film and make the ink thicker |
| Paper white or hard edge is exposed | Misregistration | Adjust registration, do not change ink |
| Only the second color completely pulls away the first color | ink picking, not ink bleeding | Check the tack and drying of the second color |
Do this first in this round
- Magnify the boundary. First determine whether it is color mixing or paper white.
- If it is color mixing, reduce the ink of the color printed first, do not add the later color to cover it.
- If the same image area has a clean boundary when switched to coated paper, then stop at the absorbency of this material and do not change the plate again.
