the refining gap a wide range of plate segment designs may be used for refining pulps at medium consistency levels sufficient open area should be available within the plate grooves 38 to allow higher amounts of pulp to radially pass through the refiner while achieving a satisfactory number of bar treatments for good pulp quality development for example the width of the grooves may be approximately twice the width of the bars and one half the height of the bars by way of example the groove width may be 2 79 mm the bar width 1 50 mm and the bar height 7 01 mm fig3 is a chart showing tensile index newton n meters m per gram versus pulp freeness milliliters for a medium consistency refining process 40 a low consistency refining process 42 and a high consistency refining process 44 the starting pulp for each of these processes is a sitka spruce lodgepole pine softwood tmp 119 ml produced using high consistency refining and treated with a 2 application of sodium sulfite na 2 so 3 the same type of refiner an andritz model twinflo iiib 20 inch diameter pump through refiner was used for the low and medium consistency refiner processes 40 42 each of these processes was produced using five passes of refining in series in the medium consistency process 40 the pulp consistency at the mc refiner was 7 8 in the low consistency.