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 occasionallyAdd agitators in the ink fountainAdd 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 filmWill 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 Wikoff Technical Solutions 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.
