Shadow marking

1. Relieve pressure on offending press.
— if it is the second press, then more pressure at first press may compensate for this.
2. If possible, free up stock.
3. Use softer rubber for cover (this will mean more frequent grinding).
4. Using a heavier felt can minimize shadow marking by providing more cushion in the nip.
— reduce felt moisture content before the press.
— use felts that have low resistance to flow to minimize pressure differences.
5. Use a shell with correctly designed suction shell hole-to-land area relationship.
— if shell is the fault and speed range is such that a shrink fabric can be used, then installing a shrink fabric may solve problem.
— blind drilling between suction holes in a suction press will give similar relief.
— a fabric press is less susceptible to shadow marking.
— a Venta-nip press will act in this regard similar to a shrink fabric press.
6. Do not use dyes with excessively preferential absorption.
7. If possible, hold sheet on wire longer.
8. Remove presser roll and/or reduce vacuum in couch.
9. Decrease size of holes or grooves in press rolls.
— grind out dished or cupped holes.
10. Check Uhle box vacuums.