Process for making a multiply and /or multilayer fibrous web

To form a multi-layer fiber web (34), especially of paper or cardboard, at least one of the two outer layers (34',34) is from a fiber material with at least one additive at the fiber surfaces. For a multi-layer paper/cardboard web, the additive is deposited on the surfaces of hollow fibers and, in addition, within the hollow fibers and at their walls. The additive includes a filling material, and the outer layers of the web have a higher filling material content than a center layer. Calcium carbonate is used as the additive or filling material at the wet fibers, or is used as a precipitate. To apply the calcium carbonate to wet fibers, a medium with calcium oxide and/or calcium hydroxide is used so that at least a portion associates with the water at the fibers. The treated fibers are exposed to carbon dioxide to give a chemical reaction with the calcium carbonate at the fiber surfaces. The calcium oxide and/or calcium hydroxide is used at a rate of 0.1-50.0 wt.% of the fiber dry weight. The fibers are treated with carbon dioxide in a closed vessel, as a gas under pressure, during a mixing phase where a high shear effect is applied to the fibers using an energy of at least 10-50 W/hr/kg based on the dry weight. The fiber material is derived in a pulper from cellulose or used paper materials, or it is a never-dried pulp. An Independent claim is included for a papermaking/cardboard production machine, to produce a multi-layer web, with stock inlet channels (36,40) charged with fiber materials where an additive is deposited on the fiber surfaces at least partially. Preferred Features: The multi-layer stock inlet assembly (28) is structured to form a web with two outer layers or a sandwich with an intermediate layer, where the pulp for the outer layers has fibers with an additive on their surfaces.