For an optimum printing result in the offset printing process, among others, the absolutely even pressure
of the printing cylinders against the entire area is the decisive factor. Irregularities lead to stripes or
cloudy spot, to thrusting and folding, to fluctuating dot gain etc. Underpacking sheets having different
thicknesses ensure the proper pressure. The accurate and uniform property of the papers as far as
possible with regard to density, surface and thickness is important.