BS ISO 8791-5:2020 pdf free.Paper and board一Determination of roughness/smoothness (air leak methods). BS ISO 8791-5 1 Scope This document specifies the Oken method for determining the smoothness of paper and board using an apparatus which complies with the Oken method, as defined in this part of ISO 8791. It is applicable to all printing papers and boards. 2 Normative references...