BARCELONA, March 1, 2002 (Viewpoint) - One of the most important factors in the production of paper is achieving a uniform product, not only in the cross direction (CD), but also the machine direction (MD). Short-term variations in paper properties usually arise from on-machine causes while processing stock flow. Longer-term variations tend to be only in the MD, and arise from three areas: upstream pulp manufacture, stock preparation operations, and on-machine water system changes. On-machine water system stability is seen as an area where great progress is being made.