Troubleshooting Guide - Pressroom UV
On Press Issue: Mottle
Potential Causes
Stock has a non-uniform surface
Solution: Use a better grade of substrate. Apply a size to seal the sheet. Use an opaque ink or an ink with better holdout.
Excessive back cylinder pressure
Solution: Reduce the pressure. Reducing the tack of the inkmay also help.
Improperly set ink form rollers or rollers on poor condition
Solution: Check the roller settings and condition.
Improper ink/water balance, usually too much water
Solution: Adjust to proper ink/water balance.
Blanket is old, worn or embossed
Solution: Replace with a new blanket.
Plate image not receptive enough or partially blind
Solution: Check plate, remake if neccessary.
Improper color rotation
Solution: Change color rotation.
Ink is not designed for the substrate
Solution: Select an ink better suited for the substrate.
The ink surface is curing. It will look mottled, chalky or low in gloss
Solution: Refer to Chalking .
