How to tell edge scum from a lookalike on a corrugated preprint
On a corrugated preprint, separate edge scum: scumming spreads into the middle of the blank. It does not stay only on the edge. Until you can tell them apart, don't adjust the press for the wrong cause. The dirt is only a ring around the image edge. The middle of the unprinted area stays clean.
On a corrugated preprint, separate edge scum: scumming spreads into the middle of the blank. It does not stay only on the edge. Until you can tell them apart, don't adjust the press for the wrong cause. The dirt is only a ring around the image edge. The middle of the unprinted area stays clean.
Name it wrong and you adjust the wrong place
The dirt is only a ring around the image edge. The middle of the unprinted area stays clean. If you call it something else, you skip this step: check impression and water. Don't add ink across the whole plate. On a corrugated preprint, the barcode and the product name decide whether you pass it. They do not decide what you call it.
How to separate them
| What you see | Closer to | How you separate |
|---|---|---|
| The dirt is only a ring around the image edge. The middle of the unprinted area stays clean. | edge scum | Name it from one white spot |
| Scumming spreads into the middle of the blank. It does not stay only on the edge. | Treat it as that other defect | Use the same adjustment |
| It sits on the barcode and the product name | Hold this spot first | Ignore the location just to name it |
Confirm on the spot
- Look with the eye or a loupe: The dirt is only a ring around the image edge. The middle of the unprinted area stays clean
- Rule out: Scumming spreads into the middle of the blank. It does not stay only on the edge.
- Check impression and water. Don't add ink across the whole plate.
