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FAQ

TROUBLESHOOTING FOR OFFSET PRINTING

MISCELLANEOUS PROBLEMS, THEIR CAUSES, AND REMEDIES

PROBLEM
DEFINITION
CAUSE(S)
REMEDY(IES)
SCUMMING
Clear areas of the plate pick up ink.

1. Insufficient amount of fountain solution.

2. Insufficient dampener-form to plate pressure

3. Dirty dampeners.
4. Fountain solution pH incorrect.
5. Oxidation of plate.

1. Increase water ratchet or speed control.

2. Readjust dampener-form to plate pressure.

3. Clean dampeners.

4. Check pH and correct if necessary.

5. Clean and gum plate.

TINTING

Uniform, light colored tint over the entire sheet.

1. Dirty dampeners.
2. Fountain pH too low.

3. Ink breaking down in fountain solution that has proper pH.

1. Clean dampeners.
2. Check pH and correct as necessary.

3. Notify ink manufactur­er; replace ink.

FILLING UP
Halftones and type fill in with ink.
1. Ink is too tacky.
2. Too much ink.
1. Reduce tack using var­nish.

2. Reduce ink flow; remove some ink from rollers.

PILING
Ink builds up on the blan­ket.
1. Ink is too tacky.

2. pH of fountain solution is incorrect.

1. Reduce tack using var­nish.
2. Check and correct pH.
SET-OFF

Ink from one sheet trans­fers to the back of the next sheet in the delivery pile.

1. Too much ink.
2. Ink lacks drier.

3. Static electricity in paper. 4. Coated paper doesn’t absorb ink quickly.

5. Fountain pH too low.
1. Reduce ink flow.

2. Use properly formulat­ed ink; add drier.

3. Use a static eliminator.
4. Use anti-set-off spray.
5. Correct pH.
PICKING

Hickies appear in image areas of the plate.

1. Ink too tacky—it pulls fibers of paper into the ink.

2. Paper has lint on the surface.
3. Stock is poorly coated.

1. Reduce tack using reducing varnish; use properly formulated ink.

2. Use better grade of paper. 3. Use better grade of paper.

ROLLER STRIPPING

Areas of ink rollers do not pick up ink.

1. pH of fountain solution too low (too strong)

2. Ink rollers are glazed (shiny)

1. Check and correct pH.

2. Remove glaze with pumice or cleanser and water, then wash rollers with water miscible solvent.

 
PROBLEM
DEFINITION
CAUSE(S)
REMEDY(IES)
SPRAYING
Ink flys off the rollers at high speeds.

1. If dots of ink appear on the press, the ink’s vis­cosity is too low.

2. If lines of ink appear on the press, the ink’s viscosity is too high.

3. Too much ink.

4. Ink rollers are worn or incorrectly set.

1. Use an ink with higher viscosity.

2. Use an ink with lower viscosity or thin ink with varnish.

3. Reduce ink flow.

4. Check condition and setting of rollers.

GREY TYPE
Printing is too light
1. Incorrect ink form roller pressure.
2. Too much water.
3. Too little ink.
1. Adjust ink-form to plate pressure.
2. Reduce water flow.
3. Increase ink flow.
CHALKING

Ink not rub-proof after drying. Will offset or scuff in some binding operations.

Ink vehicle has been absorbed by paper, leaving pigment in chalky condition on top of sheet.

Use a stiffer ink or a less absorbent paper or a faster drying agent.

RUNNING
Ink penetrates the paper.
1. Ink is too thin.

1. Replace ink with an ink with higher body.

HICKIES

Small white spots in solid areas of the image.

1. Bits of ink skin in the rollers.
2. Paper has loose fibers.
3. Ink too tacky.

4. Fibers of molleton are coming off dampener rollers.

5. Cracked ink rollers or blanket.

6. Particles of anti-setoff powder in ink.

7. Dust falling into ink rollers.

1. Avoid putting ink skin in the fountain— remove skin carefully.

2. Wind paper before loading it into the feed­er.

3. Use properly formulat­ed ink: add varnish to ink.

4. Replace worn mol­letons.

5. Check and replace worn rollers or blanket.

6. Use as little spray as possible.
7. Keep pressroom dust-free.
Mottling
Ink does not dry flat. Some areas dull and others shiny.

Paper not of same porosity all over sheet. Driers not evenly distributed in ink.

Work driers in more thoroughly. Try another paper.
No Gloss
Gloss inks dry dull.

Paper not glossy. Paper absorbs too much vehicle.

Use a high gloss paper especially suited to gloss ink printing. Adjust ink to set before too much absorption takes place.

 
PROBLEM
DEFINITION
CAUSE(S)
REMEDY(IES)
Ghosting
Indistinct image patterns appear in solids.
Poor layout of sheet. Emulsified ink. Too much water being run on plate.
Change layout. Change ink. Use less water.
Slow Drying
Ink requires excessive length of time to dry.
Too much water and too much acid used on plate. High humidity of paper and atmosphere.

Use better plates so that less water and acid are necessary.

Catch-Up
Radial band of ink appearing on non-printing areas.

Dirty or dry dampeners or parts of dampeners not touching plate.

Re-cover dampeners and re-set them.
Slur
Shadow dots and reverse letters fill up.
Over pressure or blanket too high.
Reduce pressure. Remove some packing from under blanket and put it under plate.