felt and will flow out of it without being distributed over its entire width the inclination of the felt also plays an important role in distributing the size by allowing the gravitational forces to have a greater or lesser effect this makes it possible to adjust the operation and to compensate for any shortcomings in the distribution which are due to a not entirely suitable felt the optimum correspondence between the viscosity of the size and the density of the felt is indicated in the table below in the case of a 30 u00b0 inclination of the felt with respect to the horizontal a flow length of 6 cm a distribution width of 6 cm and a cylinder pressure on the coating device of 1 bar the nature of the felt has an effect on the quality with which the size is distributed in respect of three criteria associated with the type of fiber employed the chemical nature of the fibers their diameter and their homogeneity the great majority of the fibers making up the felts are composed of cellulose fibers or wool fibers synthetic fibers are also starting to be used such as polypropylene fibers or polyester fibers in the case of size compositions whose constituents are not very polar polypropylene type synthetic felts are very suitable and the chemical compatibility is satisfactory in the case of compositions having a marked polar character which is the case with many constituent components in sizes natural.