This document specifies two procedures for the preparation of laboratory sheets prior to measuring optical properties. One is the preparation of pads in a Büchner funnel using a filter paper or a wire screen and the other one is the preparation of laboratory sheets in a standard sheet former (conventional or Rapid Köthen).


This document is applicable to all wood pulps and to most other types of pulp.


It is not applicable to pulps with very long fibres, such as those made from unshortened cotton, flax and similar materials, unless they are reduced to a suitable fibre length (about 2 mm) before performing the methods.


It is not applicable to recycled pulps (see ISO 21993).


It is not applicable to opacity measurements or to the determination of light scattering and absorption coefficients.