Editing Fountain pen (section)

===Modern filling mechanisms===
[[File:Schmidt K5 fountain pen converter + 2.5 mm 316 Stainless Steel bearing ball.jpg|thumb|Schmidt K5 piston-style standard international size fountain pen converter, containing a user inserted 2.5 mm diameter Marine grade 316 stainless steel bearing ball]]

A [[capillary action|capillary]] filling system was introduced by [[Parker Pen Company|Parker]] in the Parker 61 in 1956.<ref>{{cite journal|last=Match|first=Richard|date=September 1956|title=Things you never knew about your pen|journal=[[Popular Science Monthly]]|location=New York|volume=169|issue=3|page=278|quote=it drinks its fill automatically, by a reverse application of our old friend capillary action}}</ref> There were no moving parts: the ink reservoir within the barrel was open at the upper end, but contained a tightly rolled length of slotted, flexible plastic. To fill, the barrel was unscrewed, the exposed open end of the reservoir was placed in ink and the interstices of the plastic sheet and slots initiated [[capillary action]], drawing up and retaining the ink. The outside of the reservoir was coated with [[Teflon]], a repellent compound that released excess ink as it was withdrawn. Ink was transferred through a further capillary tube to the nib. No method of flushing the device was offered, and because of problems from clogging with dried and hardened ink, production was eventually stopped.<ref>{{cite web|url=http://www.rickconner.net/penoply/park.06.html|title=Parker 61|last=Conner|first=Rick|date=2005-01-20|work=PRick Conner|access-date=2008-08-08|archive-date=2008-10-11|archive-url=https://web.archive.org/web/20081011155054/http://www.rickconner.net/penoply/park.06.html|url-status=dead}}</ref>

Around the year 2000, Pelikan introduced a filling system involving a valve in the blind end of the pen, which mates with a specially designed ink bottle.<ref name="richardspens.com">{{cite web|last1=Binder|first1=Richard|title=Design Features: What Were They Thinking?|url=http://www.richardspens.com/?page=ref/design/what_thinking.htm|website=Richard Binder's Pens|access-date=26 July 2016|archive-date=20 August 2016|archive-url=https://web.archive.org/web/20160820164747/http://www.richardspens.com/?page=ref/design/what_thinking.htm|url-status=live}}</ref> Thus docked, ink is then squeezed into the pen barrel (which, lacking any mechanism other than the valve itself, has nearly the capacity of an eyedropper-fill pen of the same size). This system had been implemented only in their "Level" line, which was discontinued in 2006.<ref name="richardspens.com"/>

Most pens today use either a piston filler, squeeze-bar filler or cartridge.<ref name="ReferenceA">{{cite web|last1=Binder|first1=Richard|title=Filling Systems: Overview of How They Work and How to Fill Them|url=http://www.richardspens.com/?page=ref/fillers/fillers.htm|website=Richard Binder's Pens|access-date=26 July 2016|archive-date=28 July 2016|archive-url=https://web.archive.org/web/20160728213527/http://www.richardspens.com/?page=ref/fillers/fillers.htm|url-status=live}}</ref> Many pens are also compatible with a ''converter'', which has the same fitting as the pen's cartridge and has a filling mechanism and a reservoir attached to it.<ref name="ReferenceA"/> This enables a pen to fill either from cartridges or from a bottle of ink. The most common type of converters are piston-style, but many other varieties may be found today. Piston-style converters generally have a transparent round tubular ink reservoir. Fountain pen inks feature differing [[surface tension]]s that can cause an ink to [[adhesion|adhere]] or "stick" against the inside of the reservoir. Common solutions for this problem are adding a small (rust-proof) ink agitating object like a [[SAE 316L stainless steel|316L]] or [[SAE 904L stainless steel|904L]] stainless steel or [[zirconium dioxide]] [[bearing ball]], [[Spring (device)|spring]] or hollow tube in the tubular reservoir to mechanically promote free movement of the contained ink and ink/air exchange during writing. Adding a very small amount of [[surfactant]] such as [[Triton X-100]] used in Kodak Photo-Flo 200 wetting agent to the ink will chemically promote free movement of the contained ink and ink/air exchange during writing. However, ink might react adversely to adding a surfactant.

Vacuum fillers, such as those used by [[Pilot (pen company)|Pilot]] in the Custom 823, utilize air pressure to fill the ink chamber. In this case, while the nib is submerged in ink, a plunger is pushed down the empty chamber to create a vacuum in the space behind it. The end of the chamber has a section wider than the rest, and when the plunger passes this point, the difference in air pressure in the area behind the plunger and the area ahead of it is suddenly evened out and ink rushes in behind the plunger to fill the chamber.

Converters are also available in several different types such as piston, plunger, squeeze and push button in rare cases.