Mottle, ghosting, banding, hickeys: naming the print defects and knowing what caused them

When a delivery looks wrong, the conversation with the printer goes better if both sides use the same words. "It looks patchy" could be mottle, ghosting, a coating problem or a paper problem, and each has a different cause and a different remedy. This guide describes the print defects that have names, how to recognise each one on the sheet, what produces it, and whether it is something a print buyer can reasonably reject. It applies mainly to offset litho, with notes on the digital equivalents where they exist.

Mottle

What it looks like: an uneven, blotchy appearance in what should be a smooth solid or a flat tint, most visible in mid-tone greys, pale blues and large areas of a single colour. Under a loupe the dots are all there; the unevenness is in how the ink sits on the paper.

Causes: uneven ink absorption by the paper (a paper problem, common on cheaper uncoated and some recycled stocks), too much water on the press, ink and paper that do not suit each other, or back-trap mottle where a later ink unit pulls some of an earlier colour back off the sheet. Digital presses show a similar effect on rough papers when toner does not fuse evenly.

Reasonable expectation: a light, uniform texture in a large solid on uncoated paper is normal and should be visible on the proof or a sample. Heavy blotches that vary across the run are a fault.

Ghosting

What it looks like: a faint lighter or darker image of another part of the design appearing inside a solid area, usually in the direction the sheet travelled through the press. Classic case: a row of logos across the top of the sheet leaves a pale echo of themselves in a dark panel below.

Causes: mechanical ghosting happens when a heavy solid follows a pattern of lighter coverage along the same track, and the ink roller cannot recover in time. Chemical ghosting is rarer and appears on the back of the sheet, caused by ink drying vapours from the stack. Neither is a paper fault; both are layout and press management issues.

Reasonable expectation: a good printer sees the ghosting risk at imposition and rotates the image, changes the layout on the sheet or adds a take-off bar. Visible ghosting in a finished job is a fault and should be rejected.

Banding

What it looks like: on offset, distinct light or dark bars across the sheet at regular intervals, at right angles to the direction of travel. On digital and inkjet, fine horizontal lines through a gradient or a photograph.

Causes: on offset, roller problems such as a glazed or incorrectly set roller, or gear marks. On digital presses, a dirty or failing drum, or a printhead nozzle problem on inkjet. A related effect in gradients is stepping, where a smooth gradient shows visible tonal bands; that is usually in the file (an 8-bit gradient over a wide area) rather than the machine.

Reasonable expectation: banding from the press is a fault. Stepping in a gradient is a file issue the printer should have flagged at proof; it is worth adding a little noise to long gradients in the artwork.

Hickeys

What it looks like: a small solid spot, often with a pale halo around it, in an area of solid ink. A hickey is a piece of dried ink, paper dust or debris that has stuck to the plate or the blanket and prints as a ring.

Causes: dust from the paper, particles from the ink, or debris in the press. They come and go through a run as the particle picks up and drops off.

Reasonable expectation: operators remove hickeys when they see them, and a few sheets with one hickey in a large run are within normal spoilage. A hickey on every sheet in a solid is a fault. The checks the operator makes are described in our article on registration, colour bars and the press sheet.

Other defects worth knowing by name

Which defects are in the paper

Mottle, picking and show-through are as much about the paper as the press. A budget uncoated stock or a lightly coated recycled sheet will mottle in large solids and pick under tacky ink, and no press setting eliminates it. The remedy is a better sheet, a lighter ink film, or a design with fewer large flat solids. If the paper was chosen by the buyer against advice, the printer is entitled to say so. If the printer chose it, the result is theirs. Either way, a printed sample on the actual stock before the run is the only reliable way to see how a paper behaves, and our note on paper weight, caliper and bulk explains why two sheets of the same grammage can print so differently.

How to raise a defect

Keep the packaging, photograph the defect against a ruler in daylight, and count how many sheets or copies out of the delivery show it. Note whether it appears in the same place on every copy (a plate, blanket or layout issue) or randomly (dust, hickeys, handling). Send this with the job number before anything is used, and hold the stock. A printer can respond to "ghosting in the dark panel on page 3, every copy, sample attached" in an afternoon; "the brochure looks wrong" takes a week of back and forth.

Defects and our presses

Every job that runs through our digital and offset print production is checked on the press sheet against the proof for the defects above, and large solids on uncoated or recycled stocks are flagged at the quote stage with a printed sample where the risk is real. Layouts that would ghost are re-imposed before plates are made, and gradients that would step are corrected at preflight and shown on the proof. If a delivery does show a fault that is ours, the job is reprinted; the inspection points we use are listed on the printing services page. For a job where a large flat colour is central to the design, tell the team on the contact page and we will run a sample on the chosen stock first.