Structure characterisation of pigment coating layer on paper by scanning electron microscopy and image analysis

The ever rising need for detailed knowledge of the structure of paper coating urges the improvement and development of new techniques for gaining new and valuable information. The present study exemplifies how microscopy and image analysis can be applied in structural studies of the coating layer. In the study, osmium tetroxide (OsO4) was used to stain the latex binder. Image processing and analysis routines for acquiring information on the coating layer surface roughness and porosity details like the pore shape, size and orientation are described. A routine, based on the Sobel operators, for measuring the pigment particle orientation, is also described. The developed semi-automatic image analysis routines are useful methods for morphometric analysis of paper structure details, thus facilitating numerical data acquisition of the pores and the pigment particles' geometry. Pail of the obtained information is assumed to be unattainable by other methods at this point.