Abstract: A method is provided for manufacturing an end product such as, for example, paper or board from a fibrous base material such as waste paper. The method includes the steps of introducing into a pre-soaking device the fibrous base material and admixing such base material with a sufficient predetermined quantity of water to form a fibrous mixture. Controlled amounts of the mixture are thereupon introduced into a pulper and admixed with a quantity of water greater than the quantity of water introduced into the pre-soaking device so as to form a fibrous suspension. The fibrous suspension is then transported to a subsequent processing station for further processing into the desired end product.The pre-soaking device includes a mixing container, preferably a cylinder, mounted on a support frame and adapted to be tilted so as to discharge a variable amount of mixture from the cylinder as a function of the angle of inclination of the cylinder.