The present invention relates to an apparatus for the production of absorbent materials comprising fibers cross-linked by a suitable cross-linker therefor, and wherein said cross-linker is associated with substantially the entire surface of each fiber, said materials being preparable by mixing of an aerated suspension of the charged fibers with the cross-linker before heating and compressing, such fibers having a capacity for fluid absorption considerably greater than has been heretofore known for such materials.