Two layers of paper webs, which under pressure trigger an optically visible chemical reaction, give you optimal diagnosis of the condition of the rollers.
Here are a few examples of roller signatures:
Stronger impression at the end
Impression is stronger at the ends of the rolls than in the middle.
Inadequate crowning or too high applied pressure.
The sheet is dryer at the edges than in the middle. The edges of the felt run ahead of the middle. Felt wear is substantially greater at the edges than in the middle.
Stronger impression at the center
Pressure is greater at the centre of the roll than at the edges.
Excessive crowning or insufficent applied pressure.
The edges of the sheet contain more moisture than the centre. The middle of the felt runs ahead of the edges, and the density of the felt varies across the width.
Uniform pressure across the entire width
Press loading achieved regularly over the whole width.
Regular water removal from the sheet and regular moisture profile. Felt runs straight and true.