What Does a Hickey Look Like, and When Should You Stop the Press?
A hickey is a printed speck with a white ring, made by a particle on the plate or blanket. Stop when that mark repeats in the same place, or when it sits on a barcode, a drug name or a fine screen. A speck that jumps between sheets is loose dust: flag those sheets, and do not wash the plate for it. Write the smallest reject size, in millimetres, before the job starts.
The short answer
A hickey is a small printed speck with a white ring around it. A particle of dried ink, paper dust or other debris sits on the plate or blanket, prints a dot, and keeps the ink off the paper around it.
Stop the press when that mark comes back in the same place on every repeat, or when it lands on a barcode, a drug name or a fine screen. A speck that jumps from sheet to sheet is loose dust. Flag those sheets. Do not wash a clean plate because of them.
The picture shows the shape to look for: one dark speck in the centre of an unprinted ring, on an otherwise even cyan solid.
Same shape, different cause
The ring is the clue. A plain dirt spot does not usually have a clean halo. The halo means something on the printing surface is both transferring a little ink and holding the rest back.
| What you see | Usual cause | What to do |
|---|---|---|
| Same place on every repeat, speck plus a white ring | Dried ink, paper dust or debris on the plate or blanket | Stop and clean that surface |
| The speck moves between sheets | Dust falling onto the web, or dirt in the ink | Flag the bad sheets and find the source |
| A line, not a ring | A scratch, a skin of dried ink, or a nicked blade | Stop. A threshold set for round spots will miss a thin line |
Look at three repeats before you decide. One pulled sheet cannot tell a stuck particle from a random speck of dust.
When it is a reject
Size is not the whole decision. A hickey about half a millimetre across can sit quietly in a pale margin and still ruin a barcode or a line of small type. The customer circles the second one and never mentions the first.
Write the limit as a diameter, in millimetres, for the most sensitive part of this job: the barcode, the drug name, the flesh tone, the fine screen. A quiet solid can have a looser limit. One number for the whole sheet is how a press "that looked fine" ships a rejected roll.
100% inspection is what sees the repeats nobody pulled. The camera does not know which speck matters until someone sets the spot threshold to that diameter. Raising the threshold because the press "always has a few" is the decision that lets hickeys leave the building.
What to do at the press
- Compare three repeats. If the ring is in the same place, stop and clean the plate or blanket. Wiping one sheet and starting again puts the same defect back on the next thousand.
- If the speck moves, do not stop for a plate wash. Find whether dust is falling on the web or riding in the ink, and flag the sheets that already have it.
- Put the customer's smallest unacceptable diameter on the ticket before makeready, and set the camera to that number. Do not copy yesterday's threshold onto a job with smaller type.
- Keep hickeys separate from register and colour. A sheet can be inside the register window and the Delta E tolerance and still be unsellable because of one ring in the barcode.
Where to go next
- Hickey is the definition of this defect.
- 100% inspection covers why sampling misses marks that repeat for only part of the roll.
- What is print quality inspection? sets spots next to colour, register and missing print.