Troubleshooting Guide - Pressroom Conventional
On Press Issue: Back Trap Mottling
Potential Causes
Using fast setting work and turn inks
Solution: Use a more stable, slower setting ink with lower solvent content.
Dark colored inks printed on the first or second units
Solution: Change ink sequence. Run darker colors last in sequence if possible.
Solid overprinted by another solid or screen tint
Solution: Change layout and/or sequence if possible to print lighter coverage forms before heavier coverage forms.
Improper tack sequence
Solution: Use tack graded inks, printing highest tack inks first, or use properly formulated uniform tack inks.
Ink drying on rollers and blankets during long make readies
Solution: Clean press and shorten make ready times.
Excessive solvent evaporation due to fast press speeds
Solution: Reduce press speed and use fresh ink.
Running glossy substrate
Solution: High gloss substrates are prone to back trapping. Try a lower gloss substrate if possible.
Running compressible blanket
Solution: Change to a quicker release conventional blanket with high solvent resistance.
Excessive blanket squeeze
Solution: Back off pressure on back cylinder slightly.
