23 Of the Most Common Oil-Based Litho Printing Issues and How to Troubleshoot Them

1. Slurred Image or Fill-In

Your dots are elongated and reverse areas are filling in.

What it looks like

PROBABLE CAUSES

  • Incorrect printing pressure between blanket or plate cylinder
  • Loose, uneven, or soft blanket
  • Ink too soft or long body

POSSIBLE SOLUTIONS

  • Check packing to ensure kiss impression
  • Adjust or tighten blanket
  • Consult ink supplier

2. Print Crystallization

When dry trapping, succeeding colors do not take well or transfer to the first-down colors.

What it looks like

PROBABLE CAUSES

  • First-down colors are too hard-drying
  • Turn-around time is too long

POSSIBLE SOLUTIONS

  • May need a special imprint ink to adhere to crystallized prints
  • Do not let first-down ink dry for too long before applying second-down color

3. Inconsistent Print Density

You’re seeing color variation from sheet-to-sheet.

What it looks like

PROBABLE CAUSES

  • Low ink level in the fountain
  • Improper roller setting
  • Improper ink/water balance
  • Ink backing away from fountain roller
  • Roller stripping (see ink stripping section)
  • Contaminated ink fountain – dust, grit, etc, at the ink blade/roller nip

POSSIBLE SOLUTIONS

  • Keep ink fountain full to maintain head pressure
  • Reset rollers
  • Decrease water, check pH conductivity
  • Agitate ink in fountain or increase the ink flow
  • Deglaze the rollers
  • Remove ink, clean fountain, replace with fresh ink

4. Dot Gain

You’re seeing heavy halftones – the solids may have the desired density, but background screens are too heavy.

What it looks like

PROBABLE CAUSES

  • Excessive pressure
  • Too much water and/or ink on rollers
  • Ink too weak
  • Ink too soft
  • Loose blanket
  • Doubling mistaken for dot gain
  • Improper plate exposure has resulted in larger than desired dots

POSSIBLE SOLUTIONS

  • Reduce blanket packing – check pressure
  • Adjust fountain settings – reduce water
  • Increase ink color strength
  • Increase ink tack and/or body
  • Tighten blanket
  • Correct the cause of doubling
  • Remake the plate to correct for dot size

5. Ink Drying on Rollers

This one is pretty self-explanatory—your ink is drying on the press rollers.

What it looks like

PROBABLE CAUSES

  • Excessive drier in the ink
  • Light take-off
  • Roller pressure is too great, thus creating too much heat
  • Roller wash incompatible with rubber

POSSIBLE SOLUTIONS

  • Add antioxidant to slow down drying
  • Reduce ink strength to carry more ink or add take-off bars to plate
  • Adjust rollers to minimum pressure necessary to properly transfer the ink
  • Check rollerwash for rubber swell

6. Ink Drying too Slowly

Your printed sheets are taking forever to dry.

What it looks like

PROBABLE CAUSES

  • Not enough drier in the ink
  • Paper with too much holdout or wrong ink selection for stock
  • Stock too acidic, incorrect pH or fountain solution incompatible with ink

POSSIBLE SOLUTIONS

  • Add combination drier
  • Use stronger and harder-drying ink
  • Adjust pH and conductivity to specs

7. Tinting

You can see a faint tint in non-image areas.

What it looks like

PROBABLE CAUSES

  • Ink bleeding in fountain solution
  • Plate too sensitive
  • Ink too water receptive
  • Fountain solution pH and conductivity incorrect

POSSIBLE SOLUTIONS

  • Consult your ink supplier
  • Clean, re-etch and gum the plate
  • Add heavy body litho varnish
  • Remix to manufacturer’s specifications

8. Ghosting

This can come in two forms:

a. Chemical:

Image from the opposite side of the sheet is showing through due to surrounding gloss difference

What it looks like

PROBABLE CAUSES

  • Active materials in the ink can migrate to the surface and form an image on the back of the sheet
  • Oxidation can also cause gasses to migrate to the surface, forming an image on the opposite sheet or on the back side of the same sheet

POSSIBLE SOLUTIONS

  • Whenever possible, run the large solid areas first and completely finish first side

b. Mechanical:

Visible light and dark areas on the print

What it looks like

PROBABLE CAUSES

  • Ink viscosity too high
  • Ink too short
  • Ink too strong or too transparent
  • Shortage of oscillating rollers or improper image layout

POSSIBLE SOLUTIONS

  • Lower the ink viscosity
  • Add free-flowing litho varnish
  • Add extender to carry heavier ink film or use opaque ink
  • If possible, change the layout of the subject matter or use an extra print unit to separate vertical and horizontal images

9. Print Hickies

These look like small dots surrounded by a halo in solid image areas.

What it looks like

PROBABLE CAUSES

  • Ink tack too high or poor paper surface
  • Worn roller surfaces
  • Dirty printing unit (dust, grit, etc.)
  • Poorly ground ink or other impurities in ink

 

POSSIBLE SOLUTIONS

  • Reduce ink with tack reducer or thin litho varnish
  • Check rollers – replace if necessary
  • Wash up printing unit
  • Check ink grind

10. Ink Backing Away in Fountain

The ink isn’t following the fountain roll, so you can’t keep a uniform color.

What it looks like

PROBABLE CAUSES

  • Ink too short

POSSIBLE SOLUTIONS

  • Mix or stir the ink occasionally
  • Add agitators in the ink fountain
  • Add free-flow varnish or contact supplier

11. Ink Misting

Ink mist is settling around your press.

What it looks like

PROBABLE CAUSES

  • Ink too weak or has too much flow
  • Incorrect roller settings
  • Improper ink/water balance
  • Fountain solution may have strong solvent

 

POSSIBLE SOLUTIONS

  • Consult ink supplier
  • Check roller settings, re-stripe
  • Check dampening system adjustment
  • Check pH and conductivity of fountain solution

12. Print Mottling

Your image areas are splotchy and uneven.

What it looks like

PROBABLE CAUSES

  • Too much impression
  • Too much ink carried
  • Low viscosity ink may look mottled on paper with uneven holdout
  • On some stocks, transparent inks will show more mottle
  • Ink is emulsified

POSSIBLE SOLUTIONS

  • Check blanket-to-impression and plate-to-blanket pressure
  • Run a stronger ink to permit a thinner ink film
  • Higher viscosity ink will have less absorption and will reduce mottle
  • Use a more opaque ink
  • Consult ink supplier

13. Paper Picking

Paper particles become loose, collect on the blanket and plate, and are now appearing in the print.

What it looks like

PROBABLE CAUSES

  • Ink tack too high for the paper
  • Ink too strong, light ink take-off or ink drying too fast
  • Stock affected by the dampening system (not water resistant)
  • Ink and rubber incompatibility

POSSIBLE SOLUTIONS

  • Reduce ink with tack reducer or thin litho varnish
  • Add extender or transparent white to the ink to reduce strength; thicker ink film
  • Will have more lubrication
  • Change stock if possible
  • Consult ink supplier

14. Piling

Paper particles and ink have built-up on your blankets and plates.

What it looks like

PROBABLE CAUSES

  • Ink tack too high for the paper
  • Ink drying too fast or poorly ground ink
  • Underpacked blanket and/or plates
  • Poor paper surface
  • Paper surface not resistant to water
  • Fountain solution pH and conductivity

 

POSSIBLE SOLUTIONS

  • Reduce ink with tack reducer or thin litho varnish
  • Consult ink supplier and check ink grind
  • Check/adjust packing to ensure kiss impression
  • Run through an empty press unit on impression before printing
  • Change paper to different mill run if possible
  • Remix to manufacturer’s recommendations

 

 

 

15. Excessive Plate Wear

Your images are disappearing.

What it looks like

PROBABLE CAUSES

  • Ink too strong for long runs (too thin ink film)
  • Fountain solution too acidic
  • Plate or blanket packing too high
  • Ink may have poor grind
  • Plate exposure too short or too long
  • Abrasive paper particles
  • Ink emulsification and poor transfer mistaken for plate wear
  • The form roller is too tight against the plate

POSSIBLE SOLUTIONS

  • Reduce ink strength and carry more ink
  • Increase fountain solution pH
  • Check plate and blanket packing to ensure kiss impression
  • Check ink grind
  • Change to a new and properly developed plate
  • Change paper if possible
  • Ask your local Wikoff team for ink emulsification tips
  • Check form roller settings

16. Plate Scumming

Non-image areas are accepting ink and dot gain is increasing.

What it looks like

PROBABLE CAUSES

  • Ink too soft
  • Variation in fountain solution or concentration
  • Ink film too heavy
  • Dirty dampening system or improperly set dampening rollers
  • Plate poorly desensitized
  • Insufficient plate dampening

 

POSSIBLE SOLUTIONS

  • Add heavy litho varnish
  • Adjust pH to 4.0 to 4.5
  • Reduce ink film carried
  • Clean and reset dampening rollers
  • Re-etch the plate
  • Increase fountain solution volume

17. Ink Set-Off

Ink is offsetting to the next sheet.

What it looks like

PROBABLE CAUSES

  • Ink sets too slowly
  • Heavy ink film
  • Too many sheets in pile for the particular stock
  • Paper has too much hold-out
  • Fountain solution incorrect

POSSIBLE SOLUTIONS

  • Consult ink supplier; quick setting ink may be necessary
  • Use stronger ink to permit thinner film
  • Use small lifts
  • Use non-offset spray
  • Adjust to manufacturer’s recommendations

18. Sheets Sticking

Printed sheets are sticking together.

What it looks like

PROBABLE CAUSES

  • Ink dries too slowly
  • Inks do not penetrate the stock
  • Too much ink run or ink film too heavy
  • Non-absorbent stock or not enough spray powder

POSSIBLE SOLUTIONS

  • Strengthen ink and add more drier
  • Use a fast and hard drying ink
  • Run less ink film
  • Increase the amount of spray powder

19. Ink Stripping

Rollers aren’t accepting ink in certain areas.

What it looks like

PROBABLE CAUSES

  • Glazed rollers
  • Ink too water resistant
  • Too little ink carried
  • Fountain solution too acidic
  • Too much water in the roller system
  • Too much gum in fountain solution

POSSIBLE SOLUTIONS

  • Thoroughly deglaze the rollers
  • Add hydrophillic varnish to the ink
  • Carry slightly heavier ink film by reducing ink with extender
  • Increase pH of the fountain solution
  • Run minimum amount of water
  • Reduce gum in fountain solution

20. Ink Emulsification

This can cause multiple problems including poor trapping, mushy dots, loss of gloss and plate scumming. On duplicator presses water or ink from roller can “bead up” and ink will not transfer or causes scumming.

What it looks like

PROBABLE CAUSES

  • Mechanical problems with the press and dampening system
  • Ink/water out of balance
  • Ink too soft and not water resistant
  • Incorrect fountain solution concentration
  • pH too high

POSSIBLE SOLUTIONS

  • Check roller settings and dampening system
  • Decrease fountain solution volume
  • Add heavy body litho varnish or add anti-scum compound to the ink
  • Remix the fountain solution

21. Ink Trapping

You’re having trouble with poor wet trapping between colors.

What it looks like

PROBABLE CAUSES

  • Not enough tack difference between the colors
  • Second-down color is stronger than the first-down color
  • Too much water and ink combination or improper ink film thickness on rollers
  • Paper has too much holdout

POSSIBLE SOLUTIONS

  • Increase the tack and viscosity of the first-down color
  • Strengthen the first-down color or weaken the second-down color
  • Reduce the amount of water and ink
  • Try a more quickset ink

22. Ink not Transferring

You either have weak print or blanket swell.

What it looks like

PROBABLE CAUSES

  • Check blanket wash for compatibility with blanket and rollers
  • Poor transfer of ink

POSSIBLE SOLUTIONS

  • Get a wash which is compatible with rubber being used
  • Contact ink supplier

23. Uneven Solids

You’re seeing banding or striations on solid areas around the cylinder direction.

What it looks like

PROBABLE CAUSES

  • Build-up of alcohol replacement ingredient on dampening system rollers

POSSIBLE SOLUTIONS

  • Use Wikoff Dampening System Cleaner as recommended

Still not seeing the results you need on press?

Give us a call or send us a message and we’ll be happy to help you troubleshoot your oil-based litho issues. After all, happy customers are our number one priority!

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