CONDITION |
CAUSE |
CURE |
Weak Image
(On Plate or Press) |
- Too much water, or not enough ink.
- Improperly made plate eg. Incorrect exposure setting improper development, wrong chemicals used.
- Glazed ink rollers
- Insufficient pressure between plate cylinder and blanket cylinder.
- Insufficient pressure between blanket cylinder and impression cylinder.
- Gum not fully washed from plate surface.
|
- Read just ink/water balance using Fountain Solution
- Remake plate
- Clean and deglaze ink rollers (Regular use of Multiwash minimizes glaze)
- Adjust to increase pressure.
- Adjust to increase pressure.
- Remove all traces of plate gum with warm water or plate conditioner.
|
Streaks (horizontally across plate cylinder). |
- Ink or moisture form rollers set unevenly or too heavy, causing skidding or bouncing on plate.
- Improper packing under blanket.
|
- Read just roller pressures and alignment to maker’s specifications.
- Repack blanket according to press manufacturer’s instructions
|
Dark Image or Background Tone |
- Insufficient moisture being run on press.
- Too much ink.
- Moisture rollers dirty
|
- Move Fountain Solution control to increase moisture flow.
- Reduce amount of ink being run.
- Clean Rollers using Cleaner – D
|
Plate Image Wear Excessive |
- Ink or moisture form roller pressures too heavy.
- Fountain Solution too acid.
- Plate to Blanket pressure too heavy.
- Improperly developed plate.
- Plate under exposed.
|
- Readjust roller pressures to maker’s specification.
- Use a pH tester to test fountain solution.
- Readjust pressure to maker’s specifications.
- Remake plate with proper development.
- Remake plate with proper exposure
|
Scumming (ink appearing in non – image areas.) |
- Incorrect ink/water balance. (Too much ink or not enough moisture.)
- Incorrect fountain solution pH.
- Dirty moisture forms roller cover.
- Paper coating is not of right quality. (Poor water resistance of coating.)
- Incorrect plate processing.
- Improperly desensitised plate
|
- Readjust ink/water balance using fountain solution.
- Adjust fountain solution pH to read between 5.0 to 6.0.
- Clean cover using Cleaner D or fit new one, if necessary.
- Use paper with different quality coating.( Use only paper made for offset printing.)
- Remake plate using correct chemicals prescribed for plate.
Remake plate follow directions carefully for desensitising plate surface or use plate conditioner. |
Plugging) filling in or bridging of halftones, fine reverses etc.)
|
- Too much ink being run.
- Plate to blanket pressure too heavy.
- Improperly developed plate.
- Plate overexposed.
- Plates made using exhausted chemicals. (Deteriorated stock.)
|
- Reduce ink flow.
- Readjust pressure to maker’s specifications.
- Remake plate with proper development.
- Remake plate with proper exposure.
- Remake plate using fresh chemicals
|
Hickles and picking (defects in printed iamge caused by dried ink, dirt or paper fibres on plate or blanket). |
- Worn or cracked ink rollers deposit dried ink particles on to plate.
- Dirt or dust on paper.
- Dirt on Plate
- Weak paper surface.
- Ink too tacky.
|
- Remove rollers and clean thoroughly with wash. Fit new rollers, if necessary.
- Wipe slitter dust from edges of paper pile fan paper thoroughly.
- Clean paper surface.
- Use paper with stronger surface.
- Reduce tack of ink
|
Blind plate image (Image does not accept ink.) |
- Wrong plate gum used when making plate.
- Gum film on plate too heavy.
- Glazed ink rollers.
- Contaminated chemicals used during plate processing.
|
- Use correct gum.( preserving gum solution)
- Remove all traces of gum using warm water, when preserving plates, use a small amount of gum polish to think dry film.
- Clean and deglaze ink rollers.
- Remake plate using new chemicals.
|
