Reference Book
- Incorrect fountain solution.
- Glazed blankets.
- Dirty dampening rollers.
- Excessive printing pressure.
- Glazed and dirty ink rollers.
Remedies:- Add varnish to increase tack, adjust ink water balance, remake
plate, check pH of fountain solution, clean or replace blankets or rollers, reduce
plate-to-blanket and blanket-to-imression cylinder pressure.
Setoff
The transfer of ink from one sheet to the back of another on a delivery pile.
Causes are: - Too much ink carried to paper.
- Excess acid in fountain solution.
- Insufficient amount of ink drier.
- Improper ink for stock.
- Delivery pile too high.
Remedies:- Check pH of the fountain solution, add dryers to ink, change ink to
match the stock, reduce pile height.
Slurring
An unwanted accumulation of halftone dots that result in a smeared image.
Causes are: - Excessive pressure beween plate and blanket.
- Excess ink coated on paper.
- Piling of ink on paper.
- Loose fitting plate on cylinder.
Remedies:- Reduce impression cylinder pressure, reduce ink feed, use moisture-
resistant stock, re-attach plate, add reducing varnish to ink.
Tinting
Unwanted colour tint in background of image, commonly caused by
imulsification of ink in the fountain solution. Causes are: - Ink fails to repel water.
- Improper fountain solution pH.
- Improper ink-water balance.
- Plate not properly desensitized.
Remedies:- Add varnish to increase tack, check the pH of fountain solution,
prepare new plate.