between that level and the uppermost deflector 25 similarly at 3 consistency the thickness value will be approximately 0 064 inch and the flow rate past that level will be approximately 120 gallons per minute approximately 67 gallons per minute of white water will therefore drain through the wires between the 2 and 3 consistency levels leaving approximately 30 gallons per minute to be drained during travel of the wires and sheet from the 3 level to the shoe structure 20 at which the consistency is established to be 4 it is most important for optimum sheet formation that the drainage be gentle and natural rather than forced and that the wires be supported as nearly as practicable in properly converging relation in accordance with the desired gentle drainage rate the values can be approximated however and it will be seen from the calculations outlined above that approximately 80 of the drainage occurs above the 2 consistency level and that two thirds of the further drainage occurs between the 2 and 3 levels however since drainage is at a continuously decreasing rate due to retardation of the fiber mat forming in the wedge zone on the surface of each wire these figures can be approximated on the basis that the 2 consistency level should be about two thirds of the way down the wedge zone carrying these calculations further if the vertical extent of the wedge zone is 24.