Slur is characterised by the smearing of the printed image: the dots are distorted in printing direction, typically elongated, and exhibit an oval shape. This condition is caused by slippage at the point of contact and impression between the plate and the substrate and/or even the plate and the anilox roll.
The printed image appears like stretched, typically showing a halo of ink around the edges of the graphic elements, and often a void, or a lighter area, in the middle.
Slur has therefore 2 major aspects:
- deformation of the printed image;
- build-up of unwanted quantity of ink on the shoulder of the plate immediately below the printing surface.
Slur typically happens along the print direction, however, in corrugated printing, where substrate is made of single sheets, it may also appear in other directions.