Vertical Sensitivity
Micro-topographical measurement limits representing the smallest detectable vertical displacement determine the accuracy of surface roughness profiles on paper and board substrates. A system with high height resolution is required to measure the minute surface cavities and fiber protrusions that govern ink transfer and print quality. When analyzing coated papers, this parameter determines whether the instrument can resolve the thin layer of coating clay overlying the base fiber network.
Interferometers and stylus profilometers must maintain sub-nanometer vertical precision to produce reliable surface maps. Without this sensitivity, the subtle changes caused by supercalendering remain undetected.
Measurement Method
Modern paperboard testing employs optical profilometry to capture the three-dimensional structure of the sheet without damaging the fibers. The achievable height resolution of these optical sensors depends on the light source wavelength and the numerical aperture of the objective lens. With an optimized optical setup, the system can measure depressions as shallow as ten nanometers, allowing for the precise quantification of calender roll impressions and micro-embossing patterns on luxury packaging board.
Surface Characterization
Printing performance on high-speed presses is directly influenced by the micro-texture of the paperboard. Inadequate height resolution in laboratory testing fails to detect the micro-voids that cause rotogravure speckle and flexographic ink starvation. By establishing a rigorous standard for vertical precision, quality control labs can reliably predict varnish laydown and adhesive bonding performance before the stock is mounted on the press.
