In secondary fibre processing several problems are caused by fines, which are present in high concentrations in recycled pulp. One of the major problems is the decreased drainage rate, which results in a reduction of the capacity of paper machines. With enzymatic treatment the short cellulose fibres can be degraded and drainage properties of the pulp can be improved.
The aim of this study was to prepare the investigation of the influence of enzymatic treatment; the results of hydrolysis by cellulases are not shown here. The freeness (characterised by Schopper-Riegler number) of reference pulps showed great fluctuation in the parallel experiments, as this was quantified by variance components analysis. All of individual steps of the procedure were carefully examined and the method was standardised based on analysis using an Ishikawa diagram. The reproducibility and repeatability improved significantly. The required number of future replicated and repeated experiments in enzymatic treatments were calculated derived from estimated variance components of the improved process on untreated pulps.