A method and apparatus for incorporating feature substances into a still moist
but already sufficiently consolidated paper web provides for directing a feature
substance suspension onto the surface of the paper web as a laminar jet with low
jet pressure. A special pressure control circuit ensures that the jet pressure
is always constant regardless of the number of parallel feature substance suspension
jets directed onto the paper web. This makes it possible to incorporate a great
variety of line codings in paper under the same process conditions without any
visible changes in fiber structure occurring in the paper.