Pistons

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A Remington pen showing a cheap pen’s filler.

Piston filling pens come in two distinct sorts– screw and stick.  The former might also be referred to as syringe fillers, since the action is exactly the same as the medical implement; a stick, covered by a blind cap when not in use, is used to run the piston up and down in the reservoir chamber to draw ink in.  This mode of piston filler was most popular in cheap pens of the 1930s through the 1950s, and until recently had been all but forgotten apart from the least appealing of Parker’s converters.  However, the filler has recently been revived in a rather upscale way by Gate City Pens; it may appear in one of their less expensive models, but that doesn’t mean it’s a cheap pen.

The more commonly found piston filler is the screw piston.  A cynic might say that there isn’t really that much difference in this sort of mechanism, as the heart of it is still a stick with a sealing disc at one end; the stick is just machined to interact with a threaded driver that runs it up and down.  This renders it actually slower to fill than its counterpart, but since the driver mechanism can be worked by turning a false blind cap it means that there are fewer pieces of pen floating around loose on the desktop during the filling.  One needs only take the cap off, put the point in the ink, and twiddle to fill.  Strangely, some makers have chosen to have a separate knob hidden under a blind cap, which somewhat undoes this filler’s convenience.

The screw-piston is something of the gold standard of modern self-fillers, appearing in the high-end pens of most respectable German pen-makers.  It is probably the most popular mechanism in modern pens, leading some who have not looked deeply into the question to believe it is the only alternative to cartridges.

Piston filling is markedly superior to cartridges in terms of value; ink in cartridges is an order of magnitude more expensive than that in bottles.  There is a general equivalence in the amount of ink available, since only about half the barrel can be filled with ink, the rest being stuffed with mechanism.  However, the mode of ink storage means that piston fillers are as liable as eyedroppers to dribbling if the feed is not well-engineered.  Since the majority of modern piston fillers are at least not cheap (Dollar pens are a notable exception), this is usually not a problem, but it is something to be aware of, especially in the vintage stick-pistons.

Some people complain about piston fillers not fully loading their ink chamber in a single operation.  This is true, and an inescapable fact of physics.  The amount of ink the piston can draw is limited to the swept volume of the piston– any interior space the piston doesn’t actually pass through doesn’t count.  This means that older and cheaper pens with simpler feeds will actually have less air in the chamber after a fill.  If one is intent on having no air at all in the chamber, with reference to the directions below, I can suggest after step 6 turning the pen point-up, compressing the piston to drive out what air there is still within (which means ink will be trying to run down your wrist), then starting again at step 4 and leaving out step 7.  I would suggest that before doing that, a serious contemplation of the utility of some headspace in an ink chamber of this sort. 

From the TWSBI Diamond instruction sheet, 2010

Loading a Piston Filler Step by Step:

1. Get a paper towel or other pen-wiper.
2. Remove
   1. cap from ink bottle,
   2. cap from pen, and if applicable,
   3. blind cap from tail of pen.
3. Hold pen over ink and
   1. if using a stick-type piston, push the stick to the bottom of its travel, or;
   2. if using a screw-type, turn the knob at the tail to lower the piston.  This will typically be counter-clockwise, but there’s always a chance that the maker of your pen was atypical.
4. Immerse point in ink.
5. Reverse the action performed in step 3, returning the piston to top of its travel.
6. Remove the point from the ink, but keep it over the bottle.
7. Lower the piston again very slightly, expressing three or four drops of ink, then return it once more.  This will de-flood the feed.
8. Wipe point and section (aren’t you glad you did step 1?).
9. Replace caps.