Several widely recognised operational problems in papermaking have been attributed to the felt structure. All of these result from phenomena occurring at the macroscopic level, e.g. shadow and yarn-marking.⁽¹⁾ However, phenomena occurring at the microscopic level, i.e. at the scale of the individual fibres of the felt and paper, have received less attention.
Recent experimental studies⁽²⁻³⁾ on press felts show that their surface properties strongly affect water removal in wet pressing. Two mechanisms have been proposed to account for these effects : rewetting, and load uniformity. While a first approach to a quantitative discussion of the effect of felt properties on rewetting has been made,⁽³⁾ account of the structural influence on load uniformity has hitherto been considered only from a qualitative standpoint.⁽²⁻⁴⁾ In this briefnote we present some findings of a more quantitative study⁽⁵⁾ to investigate the latter problem. In this study we have evaluated felt roughness and assessed its effect on water removal.