Lewis E. Waterman was an American inventor and insurance salesman who developed a relatively leak-proof fountain pen; he patented his new invention in 1884 and revolutionized writing. Before his fountain pen, pen tips had to be tipped into ink after every few words. Waterman put an ink reservoir in the pen above the pen's metal nib (point). This reservoir would hold enough ink for a few pages of writing. There were many problems in developing the fountain pen, especially the difficulty of controlling the flow of the ink. Putting a sealed reservoir above the nib wouldn't let the ink flow, but if it wasn't sealed, all the ink would flow at once. Waterman used capillary action to replace the ink in the rubber sac with air so that the ink flowed smoothly but did not flow all at once. Also, the metals in the ink dissolved the steel pen nib, so Waterman used an iridium-plated gold nib. Waterman was also the first person to place a clip on the cap of the pen.