Fountain pen (thing)

The arrangement of the working parts of a fountain pen are as follows :-

     :     :     :
     :     :     :
     |     |#####|	
     |     |#####|  
Reservoir  |#####|  - Ink reservoir,
     |      \###/     fits tightly onto the
     |_      |#|      capillary tube on feeder bar

      _       
     |       | |    - Capillary tube
     |       | |
     |    =========
     |    =========
  Feeder  ========= - Fins which absorb excess
    Bar   =========   ink squeezed from
     |    =========   reservoir
     |     |  |  |
     |     |  |  |
     |     |  |  |  - Capillary groove
     |     |  |  |
     |_     \_|_/

     __     _____
    |      |     |  - Nib which sits on feed bar,
    |      |     |    slit aligned with
    |      |     |    capillary grove.     
   Nib     |  o  |    
    |       \ | /   - Slit
    |        \|/
    |__       *     - Nib Pellet

The reservoir feeds ink to the feeder bar, via a tight fitting seal on a capillary tube. The feeder bar passes the ink in a smooth stream to the nib, and holds any excess on channels, forced from the reservoir, by say the heat of your hand. The feeder bar supports the nib, passing the ink down through a groove, along a slit in the nib via capillary action to the nib pellet. If these two capillary channels are not aligned, the pen won't work.

The nib pellet has to be made of a very hard material, as quite a lot of wear will occur as it scrapes across the paper. Commonly Ruthenium or Iridium is used. The split in the nib gives two tines, which will bend and flex apart according to the style of the writer, giving a distinctive look to each persons handwriting; the better the pen, the better and more consistent the flex.

Source, the www.parkerpen.co.uk web site.