This technical guide is continuously updated (last updated in May 2026) based on over 15 years of daily diagnostics and troubleshooting of offset presses (including Heidelberg, Komori and Manroland systems).

All solutions have been tested in real printing and packaging plants to reduce paper waste and optimize water and ink balance.

How Do You Identify and Eliminate Hickeys (Spots and Halos) on an Offset Printing Press?

In high-speed offset lithography, a hickey is one of the most persistent print defects that directly impacts pressroom efficiency and macro-level paper waste.

Based on over 15 years of pressroom troubleshooting, managing hickeys requires understanding whether the contamination is ink-borne, substrate-borne, or environmentally driven.

As we previously emphasized if they are left uncontrolled, they cause us massive amounts of waste.

Visually, a hickey manifests in two distinct shapes: a solid dark speck surrounded by an unprinted white halo (often called a “donut” hickey, typically caused by ink skin or particles adhered to the plate or blanket) or an unprinted white void within a solid print area (usually caused by loose paper fibers or dust blocking the ink transfer).

Offset Hickey Causes & Immediate Pressroom Remedies

Defect Manifestation	Primary Root Cause	Immediate Pressroom Corrective Action
Donut Spots (Speck with white halo)	Dried ink skin in the fountain or unground pigment aggregates.	Stop the press, apply adhesive tape to the blanket to pull and inspect the particle, scrape the fountain, and install an ink-fountain screen.
White Voids (Unprinted fibers)	Paper linting, surface picking, or slitter dust from low-quality stock.	Wash blankets, reduce ink tack by adding 2% to 3% of a compatible tack-reducing gel/varnish, and check feeder dust-brushes.
Irregular Repetitive Specks	Degradation of elastomer composition on ink form rollers.	Inspect roller geometry and stripe width. Replace glazed or pitting rollers showing hardness outside the 25–30 Shore A specification.

Deep-Dive Troubleshooting: Advanced Root Causes & Press Adjustments

Ink-Borne Contamination & Fountain Hygiene

The most common cause of a hard-particle hickey is dried ink skin forming in the ink fountain or an open can.

When the ink knife scrapes the container incorrectly, these oxidized fragments enter the ink train.

To solve this, operators must thoroughly dip out the fountain.

For critical solid-density jobs, running the ink through a fine mesh strainer before loading is highly recommended.

Substrate Picking and Ink Tack Dynamics

If the surface strength of the paper (measured via IGT pick resistance) is lower than the split-tack force of the ink, the ink will literally rip fibers and coatings off the sheet.

These fibers stick to the tacky blanket, creating repetitive voids.

The Fix:Carefully adjust the rheological properties of the ink.

Introduce a maximum of 2% to 3% reducing oil or let-down varnish to lower the ink’s tack value without destroying its structural body or lithographic water-balance.

Mechanical Roller Inspection & Hickey-Pickers

Aged or poorly maintained rollers can disintegrate under high mechanical stress, releasing microscopic rubber particles into the ink train.

Check your roller settings – ensure the ink form-to-plate setting creates a uniform stripe width of 3mm to 4mm.

If the rollers are glazed or have hardened well past 30 Shore A, they lose their ability to trap small debris.

For continuous long-run production, utilizing a dedicated hickey-picker roller (a form roller with a specialized dual-durometer elastomer surface) or an integrated Delta-damping system will actively hunt and sweep particles off the plate, moving them into the dampening solution before they reach the blanket.

Finally, it should be noted that sometimes, despite all your efforts, the only solution will be to change the paper/cardboard.

What Causes Paper Picking and Surface Cratering in Offset Printing, and How Do You Prevent It?

Paper picking (also referred to as plucking) is a critical lithographic defect that occurs when the mechanical splitting force of the ink film exceeds the surface tensile strength or coating adhesion of the paper substrate.

When this split-second force exceeds the material threshold, fragments of the coating or underlying wood fibers are physically torn away from the sheet during the impression cycle.

This material adheres directly to the offset blanket, leaving a permanent color void or an unprinted “surface crater” on all subsequent sheets.

Troubleshooting Paper Picking & Contamination

When picking occurs, it quickly compounds into severe blanket contamination. Use this structured matrix to diagnose and solve the problem mid-run:

Defect Manifestation	Primary Root Cause	Immediate Pressroom Corrective Action
White craters/voids appearing progressively	Ink tack is mathematically higher than the paper’s surface strength (IGT pick value).	Wash the contaminated blanket. Reduce ink tack by compounding 1% to 3% of a tack-reducing gel or let-down varnish into the ink fountain.
Flaking, linting, or dusting across solid zones	Defective paper coating formulation or weak internal binders.	Reduce impression cylinder squeeze by 0.02mm to 0.05mm. If the issue persists, isolate the paper batch and switch production runs.
Accelerated picking on multi-color units	Ink drying too rapidly on the roller train (premature oxidation/trapping imbalance).	Add a minimal amount of ink retarder or anti-oxidant compound to slow down oxidative tack buildup on the rollers.

Dive Technical Analysis: Tack Dynamics and Mechanical Adjustments

1. Controlling Ink Rheology and Tack Values

Modern offset inks are engineered with high tack values to ensure sharp dot reproduction, but temperature fluctuations can cause tack to skyrocket.

On an Inkometer or Tack-o-Scope, a standard ink might run at a tack value of 12 to 15. If the paper has low surface cohesion, you must lower this value.

Technical Caution: Never add more than 3% of liquid reducers or oils.

Over-reducing the ink will compromise its viscosity, ruin the emulsification balance (water-to-ink ratio), and lead to secondary issues like dot gain or misting.

2. Optimizing Mechanical Impression Squeeze

Excessive mechanical pressure between the blanket and impression cylinders exacerbates picking forces.

Check your cylinder packing sheets carefully.

Standard blanket-to-paper squeeze should idealistically hover between **0.10mm and 0.12mm**.

If you are over-packed, the increased “nip” width creates an aggressive surface exit angle, tearing weak paper fibers.

Dropping the squeeze by a few microns can drastically reduce the shearing forces while maintaining proper solid density transfer.

3. Assessing Substrate Integrity & The IGT Test

Often, the root cause lies entirely within the paper mill’s coating line.

Low-quality coated papers can suffer from poorly bound calcium carbonate or clay coatings.

Before rejecting a batch, ensure the press room is kept at a stable relative humidity of 45% to 55% and a temperature of 20°C to 22°C.

Dry paper loses its structural elasticity, making it highly susceptible to surface picking.

If the paper cannot withstand a standard tack ink after environmental acclimatization, a roll/pallet swap is mandatory.

What Causes Ink Pilling and Tail-Edge Picking, and How Can You Eliminate Blanket Buildup?

Ink pilling and tail-edge picking are complex multi-unit lithographic phenomena where ink, varnish, or weakened substrate coating progressively builds up on the rubber blanket, rollers, or printing plate.

Over a production run, this dry or highly viscous buildup alters the mechanical transfer profile, eventually lifting portions of the image, causing patchy print densities, destroying fine details, or leaving complete color voids.

Pilling can manifest in both halftone screens and solids, but it is fundamentally prominent on large solid fields, typically clustering at the back side (tail edge) relative to the print direction.

Root Causes of Pilling & Immediate Operational Fixes

Pilling is heavily tied to multi-color ink trapping dynamics and ink/water stability.

Use this technical diagnostic matrix to resolve piling issues on the fly:

Defect Manifestation	Primary Root Cause	Immediate Pressroom Corrective Action
Heavy ink buildup in the exact shade of the active unit	Weak water-emulsifying capability of the ink, causing surface water to soften paperboard coating.	Optimize the ink/water balance. Switch to an ink formulation with stable water-emulsification behavior to prevent dampening chemistry accumulation.
Buildup appearing on a subsequent printing unit	Ink-setting speed is too aggressive or tack sequence is incorrect across units.	Formulate with a lower-tack or slower-setting ink. If possible, rearrange the color sequence to position unstable colors toward the end.
Severe tracking/picking when running UV inks	Extremely high inherent tack of UV chemistry picking low-strength coatings.	Clean blankets at shorter intervals. Introduce highly compatible UV-safe tack reducers or switch to “quick-release” compressible blankets.

Deep-Dive Technical Analysis: Trapping Chemistry and Thermal Variables

1. Multi-Color Ink Splitting and Back-Trapping Mechanics

In high-speed, multi-color offset printing, inks applied at the initial printing units are subjected to immediate mechanical splitting as they pass through subsequent impression nips.

During this high-shear split, the sticky rubber blanket of the downstream unit picks up small particles of ink and varnish from the previously printed layer.

This back-trapping creates a rapid paste buildup.

The Fix: You must strictly manage the ink tack sequence.

The first down ink must always possess the highest tack, with subsequent units stepping down by at least 1 to 2 tack units to facilitate flawless trapping and minimize splitting residue

2. Waterlogging and Fountain Solution Emulsification Failure

When an ink has weak water-emulsifying properties, it can become waterlogged, meaning it carries excessive surface water rather than incorporating a tight, microscopic emulsion.

This free-floating dampening water comes into direct contact with the substrate, softening the paperboard’s clay coating.

The compromised coating is then easily sheared away by the blanket’s tack.

Check your dampening chemistry parameters meticulously: keep fountain solution conductivity within your additive specifications and monitor alcohol/substitute levels.

If the buildup on the blanket matches the color of that specific unit, the ink’s rheology is failing against the dampening water line.

3. Mechanical Cylinder Packing and Thermal Lag (Cold Startups)

Improperly packed plate or blanket cylinders create surface speed mismatches (slippage) within the nip zone, generating excessive friction that bakes the ink into a pile.

Ensure your cylinder packing matches the exact undercut specifications of the press manufacturer to guarantee a true rolling line.

Thermal Variables:Pilling occurs frequently after a weekend or prolonged standstill.

When the press room, ink fountain, dampening water, or paperboard stock are cold, ink viscosity and tack values are exponentially higher.

Always allow sufficient time for the complete mechanical press assembly and consumable materials to reach a stable operational temperature of 20°C to 22°C before initiating a high-speed production run.

Utilizing modern ‘quick release’ blankets with dedicated micro-cavity structures will further assist in smooth web/sheet release, minimizing tail-edge stress.

     Remedies:

•  Try a lower tack or lower set rate of ink.
• Add anti-oxidant or retard ink-drying.
•  Change ink.
• Adjust dampener settings.
•  Check specifications and adjust cylinders.
• Treat blanket or change to less tacky blanket.
• Change blanket wash.
• Clean up the rubber blankets (wash-up). Run the work with much more repeated wash-up intervals
• Run the press with ideal ink/water stability
• Select any good ink which includes much better water-emulsifying capability
• Ink could have weak water-emulsifying ability; transporting dampening water with itself (surface water).The water softens paperboard coating.
• Test if the buildup shows up about the same color as it is observable – this may recommend that the ink features a weak water-emulsifying quality.
• Determine should the buildup shows up on the following blanket – this might tell you an ink-setting trouble
• Select much less tacky as well as slower-setting inks
• Tacky ink is lifting small particles that came from the coating – resulting from excessive tack, UV inks are classified as the most critical.
• Change the printing velocity
• Reduce the interaction between a sheet and rubber blanket through the use of \”quick release\” type blankets.
• Rubber blanket might not release a sheet easily.
• Look at the compatibility of your ink as well as the dampening water together with the ink manufacturer
• You might be feeding an excessive amount of dampening water, or the dampening water is extremely hard.
• Test whether it is possible to adjust the printing order to ensure that unsettling color is a bit more toward the end the sequence
• Allow time for the full printing procedure to warm up. The press completely, ink, dampening water or paperboard may be cold after weekend or other prolonged standstill.

Dust

Loose dust particles on the paper surface adhere to the blanket, take on ink and print as dark specks, or show up  as voids in print.

Causes:

• Dust deposits can occur during sheeting or trimming operations.

Remedies:

• Predust on impression with a dry, blank unit.
• Inspect all four sides of paper for cut quality.
• wipe edges with a glycerine or tack cloth.
• trim paper on all four sides or replace with a different production run of paper.

Ghosting

Situation where printing form elements other than the desired positive or negative ones duplicate themselves onto the printed surface.

These “stencils” or “ghost images” emerge from repeated passes of the ink form roller over the plate cylinder, and from a reduction or accumulation of ink.

Causes:

•  Poor job layout
•  Ink film too thin
•  Ink too transparent
•  Used (hard) or poorly adjusted ink-rollers

Remedies:

• Improve job layout
• Consult ink manufacturer to weaken ink for heavier film or  to reformulate ink for greater opacity.
• When maintaining rollers, only use the appropriate cleansing agents; a weekly application of wash paste removes lime deposits, and will regenerate the rollers.
• Change used rollers: the rubber surface of older rollers will become glossy and over-smooth. At the same time, as their hardness increases, the edges bulge out in a trumpet shape. More pronounced abrasion becomes evident.
• An optimal balance between ink and dampening solution helps prevent ghosting.

Mottling

Solid areas are not of uniform density, resulting in uneven appearance (cloudy print output).

The problem originates in paper that is partially uneven, and the resulting uneven absorption and back split characteristics.

If the paper is spotted, or if a certain amount of cloudiness is already present in the coating, then the printing ink will be only partly absorbed.

In 4-color sheetfed offset printing, the printing result will back split on the printing blankets of the subsequent printing units.

When an uneven penetration of printing ink is especially pronounced, this will become visible after the back split process occurs, as an uneven print reproduction.

The problem of a “cloudy printout” manifests itself in the greatest variety in offset printing.

Causes :

• Non-uniform stock surface
• Improper printing pressure
• Improperly set or worn form rollers
• Improper ink/water balance
• Worn blanket

Remedies:

• Consult paper manufacturer to change stock; consult ink manufacturer for ink  for less penetration, strength
• Adjust printing pressure
•  Adjust rollers to proper setting; replace if necessary
• Adjust to proper ink/water balance
• Replace blanket.

Smashed Blanket

Sometimes a foreign object or a paper defect can actually smash, or render useless, a blanket or a plate.

The only remedy is to clear away whatever has caused the damage, spot-check the remaining paper and replace the blanket or plate.

Delamination

Causes:
If the internal bond of the paper cannot withstand the tack of the ink or other printing forces, the sheet will delaminate.

 Remedies:
Reduce ink tack on the rolls, reduce impression squeeze or try a different production run of paper.

More on-press troubleshooting’s and their solution you may find here:

 Common Offset Printing Problems and How to Solve Them