Surface quality

General informations

The smoothness or roughness of a paper indicates the extent of deformation in the plane of the paper surface. This indicator incorporates the depth, amplitude and number of deformations in this plane.

The term “roughness” is used when an increase in the value measured indicates a deterioration in surface quality. Conversely, “smoothness” is used when an increase in this value indicates an improvement in surface quality.

The measurement can be performed either using a flow of air (the methods most widely used in papermakers’ laboratories), or through surface mapping (for more detailed analyses or appraisals).

Technical Data and Achievements

Several measurement methods can be implemented at the CTP:

The roughness or smoothness of a paper can be measured by directing a flow of air through the gap between a flat surface and the paper surface. The tests can be performed using the following methods, depending on the paper surface quality:

• Roughness: Bendtsen method, in accordance with ISO 8791-2
• Smoothness, Bekk method, in accordance with ISO 5627

The roughness or smoothness of a paper can also be analysed by mapping its surface, in order to assess specific defects or analyse the surface in detail.

• Surface topography using a Topo 3D device. Roughness parameters Ra, Rz, reconstruction of the image in 2D and 3D.

Roughness test using the Bendtsen method		3D topography