Can Decorating Ghosting: Ink Distribution and Form Roll Contact
A faint shape appears inside a solid printed area on a decorated can. If it matches a blank area elsewhere in the artwork, the defect may be can decorating ghosting.
Ink left unused at a non-image area can remain on the form roll and be released during its next turn, creating a faint impression in another printed area.
Start by matching the ghost to the artwork and identifying the affected color. A shifted second outline around the entire design suggests a different problem, such as registration or double impression.
For a suspected ghost, compare its distance from the original blank area with the form-roll diameter. Then examine the ink-film response and contact records to decide where the investigation should continue.
Find the Blank Area That Matches the Ghost
Compare the defective can with the artwork for the affected color. Look for a blank area with a similar shape, then compare their positions along the printing direction.
For example, a blue design contains a small unprinted rectangle followed by a large solid area. If a faint rectangle appears within that solid, mark both positions on the artwork.
Compare the result with an acceptable can printed from the same design. Check whether the ghost stays in the same position and whether it appears in one color or several.
If only the blue separation shows the defect, start with the blue inking station. If several colors are affected, compare each one with its own artwork before assuming they share the same cause.
A photograph showing the ghost beside the corresponding artwork is useful for the next check.
Why Unused Ink Reappears on the Next Turn
The form roll carries an ink film to the printing plate. Image areas take ink from the roll. Where the plate has a non-image area, some ink remains unused on the corresponding roll surface.
The ink film is now uneven. The areas that supplied ink have less remaining, while those aligned with the blank artwork retain more.
As the form roll rotates, the ink is redistributed. If the difference remains when the same roll surface reaches another image area, the retained ink can be released and change the local print density.
The earlier blank shape then appears as a ghost.
This effect is often easier to see in dark solids. A design with a large blank area followed by heavy solid coverage may make the difference particularly noticeable.
Compare the Ghost Distance with Form-Roll Diameter
In the metal-packaging ghosting mechanism described by Sun Chemical, the distance between the original non-image area and the ghost corresponds to the form-roll diameter.
Mark the two matching features on the artwork. Compare their separation with the recorded diameter of the form roll serving that color, using consistent measurement references and the actual machine arrangement.
The relevant comparison is with roller diameter, not circumference.
A matching relationship supports the ink-carryover mechanism. The next question is whether ink distribution, roller contact, or another press condition is making the ghost visible.
If the spacing does not fit, check the artwork positions and roller arrangement again before using the diameter relationship to guide further work.
What the Ghost Pattern Tells You
| Lo que ves | Lo que sugiere | Next check |
|---|---|---|
| The ghost matches a blank area in the artwork. | Unused ink may be carried into the next turn. | Compare the ghost spacing with form-roll diameter. |
| The ghost changes after an ink-film adjustment. | Ink distribution or transfer may be involved. | Compare the affected color with earlier acceptable prints and recorded ink conditions. |
| The defect stays with one form-roll station and varies across the print width. | Uneven contact deserves attention. | Check contact records, parallelism, and the old roller’s condition. |
Separate Ink-Film Changes from Contact Problems
Start with the Affected Color
Low ink-film weight, poor ink transfer, and excessive ink strength are recognized contributors to metal-packaging ghosting.
Compare the defective print with an earlier acceptable print using the same artwork. Look at the recorded ink supply, viscosity, flow, and color condition.
If an approved ink adjustment makes the ghost less visible, examine whether the ink film is being supplied and transferred consistently. Compare the results under the same artwork and printing conditions.
The artwork itself can provide another clue.
Suppose one design prints normally, while another produces a ghost at the same color station. The second design has a large blank area followed by a solid. Its distribution of image and non-image areas may be creating a more difficult ink-film condition.
If the contact records are consistent across both jobs, investigate the ink and artwork relationship first.
A change after an ink adjustment provides useful evidence, but contact records are still needed when the problem persists.
Check Pressure and Parallelism at the Form Roll
Low contact pressure can weaken ink transfer. Poor parallelism can produce different contact conditions at the two ends of the form roll. Both are known ghosting-related factors.
Compare the affected station’s existing contact records with the press manufacturer’s requirements.
Look for a relationship between the print and the contact pattern. For instance, if the ghost is stronger on one side of the printed area and the contact record shows weaker contact at the corresponding end, that station deserves a closer look.
The timing is useful too. A defect that began after roller replacement or a documented positioning adjustment gives you a specific change to investigate.
Where installation or positioning is incorrect, the machine-side correction should follow the equipment manufacturer’s procedure. If the installation meets requirements but contact remains uneven, examine the form roll itself.
Where form-roll evidence points to a roller-related issue, send Wolorin your drawings, dimensions, or sample for quotation or manufacturing confirmation. With incomplete details, start with ghost and old-roll photos, roller position, contact medium, and the current roller-related problem.