Wikoff Blog

Got Oil-Based Litho Printing Issues? Let’s Fix Them

by Wikoff|06.17.22

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There’s no greater nightmare for a printer than when a deadline meets a problem on press. The good news is, whatever technical issue you’re dealing with, we’ve surely seen it and solved it in the past.

Here are the 23 most common oil-based litho issues and potential solutions as identified by the Wikoff Technical Solutions team. We hope this easy-to-follow guide helps you to quickly work out the kinks that are holding you back.

1. Slurred Image or Fill-In

Your dots are elongated and reverse areas are filling in.

POSSIBLE CAUSE

POSSIBLE SOLUTION

Incorrect printing pressure between blanket or plate cylinder
Check packing to ensure kiss impression
Loose, uneven, or soft blanket

Adjust or tighten blanket
Ink too soft or long body
Consult ink supplieradditive*

2. Print Crystallization

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

POSSIBLE CAUSE

POSSIBLE SOLUTION

First-down colors are too hard-drying
May need a special imprint ink to adhere to crystallized prints
Turn-around time is too long
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.

POSSIBLE CAUSE

POSSIBLE SOLUTION

Low ink level in the fountain
Keep ink fountain full to maintain head pressure
Improper roller setting
Reset rollers
Improper ink/water balance
Decrease water, check pH conductivity
Ink backing away from fountain roller
Agitate ink in fountain or increase the ink flow
Roller stripping (see ink stripping section)
Deglaze the rollers
Contaminated ink fountain – dust, grit, etc., at the ink blade/roller nip
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.

POSSIBLE CAUSE

POSSIBLE SOLUTION

Excessive pressure
Reduce blanket packing – check pressure
Too much water and/or ink on rollers
Adjust fountain settings – reduce water
Ink too weak
Increase ink color strength
Ink too soft
Increase ink tack and/or body
Loose blanket
Tighten blanket
Doubling mistaken for dot gain
Correct the cause of doubling
Improper plate exposure has resulted in larger than desired dots
Remake the plate to correct for dot size
Incorrect screen percentage
Check screen percentage

5. Ink Drying on Rollers

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

Possible Cause

Solution

Excessive drier in the ink
Add antioxidant to slow down drying
Light take-off
Reduce ink strength to carry more ink or add take-off bars to plate
Roller pressure is too great, thus creating too much heat
Adjust rollers to minimum pressure necessary to properly transfer the ink
Roller wash incompatible with rubber
Check rollerwash for rubber swell

6. Ink Drying too Slowly

Your printed sheets are taking forever to dry.

POSSIBLE CAUSE

POSSIBLE SOLUTION

Not enough drier in the ink
Add combination drier
Paper with too much holdout or wrong ink selection for stock
Use stronger and harder-drying ink
Stock too acidic, incorrect pH or fountain solution incompatible with ink
Adjust pH and conductivity to specs

7. Plate Tinting

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

POSSIBLE CAUSE

POSSIBLE SOLUTION

Ink bleeding in fountain solution
Consult your ink supplier
Plate too sensitive
Clean, re-etch and gum plate
Ink too water receptive
Add heavy body litho varnish
Fountain solution pH and conductivity incorrect
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

POSSIBLE CAUSE

POSSIBLE SOLUTION

Active materials in the ink can migrate to the surface and form an image on the back of the sheet
Whenever possible, run the large solid areas first and completely finish first side
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

b. Mechanical –Visible light and dark areas on the print

POSSIBLE CAUSE

POSSIBLE SOLUTION

Ink viscosity too high
Lower the ink viscosity
Ink too short
Add free-flowing litho varnish
Ink too strong or too transparent
Add extender to carry heavier ink film or use opaque ink
Shortage of oscillating rollers or improper image layout
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.

POSSIBLE CAUSE

POSSIBLE SOLUTION

Ink tack too high or poor paper surface
Reduce ink with tack reducer or thin litho varnish
Worn roller surfaces
Check rollers – replace if necessary
Dirty printing unit (dust, grit, etc.)
Wash up printing unit
Poorly ground ink or other impurities in ink
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.

POSSIBLE CAUSE

POSSIBLE SOLUTION

Ink too short
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.

POSSIBLE CAUSE

POSSIBLE SOLUTION

Ink too weak or has too much flow
Consult ink supplier
Incorrect roller settings
Check roller settings, re-stripe
Improper ink/water balance
Check dampening system adjustment
Fountain solution may have strong solvent
Check pH and conductivity of fountain solution

12. Print Mottling

Your image areas are splotchy and uneven.

POSSIBLE CAUSE

POSSIBLE SOLUTION

Too much impression
Check blanket-to-impression and plate-to-blanket pressure
Too much ink carried
Run a stronger ink to permit a thinner ink film
Low viscosity ink may look mottled on paper with uneven holdout
Higher viscosity ink will have less absorption and will reduce mottle
On some stocks, transparent inks will show more mottle
Use a more opaque ink
Ink is emulsified
Consult ink supplier

13. Paper Picking

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

POSSIBLE CAUSE

POSSIBLE SOLUTION

Ink tack too high for the paper
Reduce ink with tack reducer or thin litho varnish
Ink too strong, light ink take-off or ink drying too fast
Add extender or transparent white to the ink to reduce strength; thicker ink film
Will have more lubrication
Stock affected by the dampening system (not water resistant)
Change stock if possible
Ink and rubber incompatibility
Consult ink supplier

14. Piling

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

POSSIBLE CAUSE

POSSIBLE SOLUTION

Ink tack too high for the paper
Run through an empty press unit on impression before printing
Ink drying too fast or poorly ground ink
Consult ink supplier and check ink grind
Underpacked blanket and/or plates
Check/adjust packing to ensure kiss impression
Poor paper surface
Consult ink supplier and check ink grind
Paper surface not resistant to water
Run through an empty press unit on impression before printing
Fountain solution pH and conductivity
Change paper to different mill run if possible
Remix to manufacturer’s recommendations

15. Excessive Plate Wear

Your images are disappearing.

POSSIBLE CAUSE

POSSIBLE SOLUTION

Ink too strong for long runs (too thin ink film)
Reduce ink strength and carry more ink
Fountain solution too acidic
Increase fountain solution pH
Plate or blanket packing too high
Check plate and blanket packing to ensure kiss impression
Ink may have poor grind
Check ink grind
Plate exposure too short or too long
Change to a new and properly developed plate
Abrasive paper particles
Change paper if possible
Ink emulsification and poor transfer mistaken for plate wear
See remedy for ink emulsification on reverse side
The form roller is too tight against the plate
Check form roller settings

16. Plate Scumming

Ink is offsetting to the next sheet

POSSIBLE CAUSE

POSSIBLE SOLUTION

Ink too soft
Add heavy litho varnish
Variation in fountain solution or concentration
Adjust pH to 4.0 to 4.5
Ink film too heavy
Reduce ink film carried
Dirty dampening system or improperly set dampening rollers
Clean and reset dampening rollers
Plate poorly desensitized
Re-etch the plate
Insufficient plate dampening
Increase fountain solution volume

17. Ink Set-Off

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

POSSIBLE CAUSE

POSSIBLE SOLUTION

Ink sets too slowly
Consult ink supplier; quick setting ink may be necessary
Heavy ink film
Use stronger ink to permit thinner film
Too many sheets in pile for the particular stock
Use small lifts
Paper has too much hold-out
Use non-offset spray
Fountain solution incorrect
Adjust to manufacturer’s recommendations

18. Sheets Sticking

Printed sheets are sticking together.

POSSIBLE CAUSE

POSSIBLE SOLUTION

Ink dries too slowly
Strengthen ink and add more drier
Inks do not penetrate the stock
Use a fast and hard drying ink
Too much ink run or ink film too heavy
Run less ink film
Non-absorbent stock or not enough spray powder
Increase the amount of spray powder

19. Ink Stripping

Rollers aren’t accepting ink in certain areas.

POSSIBLE CAUSE

POSSIBLE SOLUTION

Glazed rollers
Thoroughly deglaze the rollers
Ink too water resistant
Add hydrophilic varnish to the ink
Too little ink carried
Carry slightly heavier ink film by reducing ink with extender
Fountain solution too acidic
Increase pH of the fountain solution
Too much water in the roller system
Run minimum amount of water
Too much gum in fountain solution
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.

POSSIBLE CAUSE

POSSIBLE SOLUTION

Mechanical problems with the press and dampening system
Check roller settings and dampening system
Ink/water out of balance
Decrease fountain solution volume
Ink too soft and not water resistant
Add heavy body litho varnish or add anti-scum compound to the ink
Incorrect fountain solution concentration
Remix the fountain solution
pH too high

21. Ink Trapping

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

POSSIBLE CAUSE

POSSIBLE SOLUTION

Not enough tack difference between the colors
Increase the tack and viscosity of the first-down color
Second-down color is stronger than the first-down color
Strengthen the first-down color or weaken the second-down color
Too much water and ink combination or improper ink film thickness on rollers
Reduce the amount of water and ink
Paper has too much holdout
Try a more quickset ink

22. Ink not Transferring

You either have weak print or blanket swell.

POSSIBLE CAUSE

POSSIBLE SOLUTION

Check blanket wash for compatibility with blanket and rollers
Get a wash which is compatible with rubber being used
Poor transfer of ink
Contact ink supplier

23. Uneven Solids

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

POSSIBLE CAUSE

POSSIBLE SOLUTION

Build-up of alcohol replacement ingredient on dampening system rollers
Use Wikoff Dampening System Cleaner as recommended

Still Need Help?

If these troubleshooting tips fail to resolve your problem, the Soluções Técnicas Wikoff team is happy to help you work through any oil-based litho printing issues that are holding you back. Give us a call or send us a message and together we’ll get your press to where it needs to be. We are your experts, and here for you when you need us.

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