consistency typically of about 0 2 u201c white water u201d is the water that is removed from the wet stock on wire 30 the consistency of the stock exiting the stock preparation unit 52 is measured with sensor 56 and signals therefrom can be employed to control the flow of filler the thin stock 62 is provided to headbox 8 a long circulation path 64 provides recycled material to stock preparation unit 52 for recovery fillers including chemical additives can be added at different steps in the process wet end chemical and mineral additives include for example acids and bases alum sizing agents dry strength adhesives wet strength resins fillers coloring materials retention aids such as polyacrylamides fiber flocculants defoamers drainage aids optical brighteners pitch control chemicals slimicides and specialty chemicals precipitated calcium carbonate can be used as filler paper manufacturers use fillers to enhance printability color and other physical characteristics of the paper the term u201c dry weight u201d refers to the weight of a material excluding any weight due to water per unit area paper is generally made of three constituents wafer wood pulp fiber and ash u201c ash u201d is defined as that portion of the paper that remains after complete combustion in particular ash may include various mineral components such as calcium carbonate titanium dioxide and clay a major component of clay is sio 2 the term u201c water weight u201d refers to the mass or weight of water per unit area of the wet paper stock that is on the wire the term u201c basis weight u201d refers to the total weight of the material per unit area during normal operations of the papermaking machine 2 fig1 scanner measurements control operations.