FP Fill Mechanisms

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Before fountain pens came dip pens. These pens had to be constantly re-dipped in ink to continue writing. The fountain pen ended this frustration. But, which fountain pen fill mechanism is best for you? The quest for the perfect fill mechanism is as old as the fountain pen itself. Over the years a great number of fill mechanisms have been invented and mass produced but in this article we will focus on a few of the most common among fountain pens still produced today. I will also share some pros and cons of each mechanism.

1) Cartridge-filled pens

Cartridge filled pens receive ink from a small plastic ink filled "cartridge" that is inserted into the pen inside the barrel. This is probably the simplest fill mechanism since a bottle of ink and clean up cloth are not required. You just pop in the cartridge, screw on the barrel and start writing. However, there are two major drawbacks: cost and ink supply. Ink cartridges are far more expensive than filling from a bottle and a typical ink cartridge only holds around 1 to 1.5ml of ink. (For comparison an eyedropper can hold 4 or more times that much.) So, it will be wise to always have a spare cartridge around for when you run out. The cartridge-filled pen is a great choice if you often need to fill your pen on the go or hate to get ink on your fingers but not a great choice if you are looking for a pen with longer writing capacity or would prefer to save money on ink in the long run.

2) Converter-filled pens

I mention converter immediately after cartridge pens because they are related. A converter is basically a refillable cartridge. In fact, most pens that take cartridges also come with a converter or one can be acquired for an extra cost. A converter slides into the pen much like a cartridge. To fill you put the tip of the pen up to the section in ink and either twist or "plunge" the converter. Some converters fill by twisting the stem of the converter while others have a plunger that moves up and down. Either way the result is the same. A converter will hold about the same amount of ink as a cartridge but allows you to use ink from a bottle. Another benefit is that the ink sucks up into the pen, thus flushing the nib a bit as you fill.

3) Aerometric/press bar-filled pens

Aerometrics and press bars are filled by a rubber or silicone bladder called a "sac" that is depressed by a metal bar. As the bladder expands ink is drawn through the nib and feed into the pen. You will need to unscrew the barrel from the section to reveal the "aerometric" device. Once the metal bar is depressed and released the bladder expands and sucks ink through the nib and into the pen. This fill mechanism was made popular by the Parker company in the 50’s and 60's but is less common in today's pens. Aerometrics are pretty easy to fill and the bladders are not prone to wearing out quite like some of the earlier fill mechanisms. And, depending on the size of the bladder you may get more ink than a cartridge will offer.

4) Piston filled pens

I'm not sure what percentage of fountain pens manufactured today are piston-filled. But, I can tell you that piston-filled pens are likely the most popular among avid fountain pen users. A piston-filled pen fills by unscrewing the end of the barrel. which causes a "piston" to descend in the body of the pen. Once the piston is fully extended the pen should be dipped in ink up to the section. Then the end of the barrel is screwed back in causing the piston to retract and suck ink into the body of the pen. The beauty of the piston pen is that you get all the ease of a converter or aerometric pen but more ink capacity. Since the body itself is the ink reservoir this allows more space for ink. The drawback of a piston pen is if the end of the pen is accidentally twisted you can end up with an inky mess.

5) Eyedropper-filled pens

Eyedroppers are less common among Western pen manufacturers but they are the go-to design in Eastern pens. On an eyedropper pen the body itself is the ink reservoir. To fill these pens you unscrew the section from the body and use an eyedropper or syringe to fill the body with ink. Then simply screw the section back into the body. You can't get much simpler. The drawback of eyedropper pens is that they can tend to "burp" ink once the ink level gets low in the pen. This is caused by the air inside the pen expanding from the heat of the user's hand and pushing out some ink. Also, ink can leak out of the threads of the section of an eyedropper if not properly sealed with silcone grease. However, a big advantage is huge ink capacity. The determiner of ink capacity is the size of the barrel. So a large pen might hold up to 5 or 6ml of ink, though around 3 to 4ml would be more normal. This is a great choice if you need to get a lot of writing in between fills.

Again, there are many more fill mechanisms that have been used over the years... over 25 that I know of. But most of those are not commonly manufactured today. The above fill mechanisms should comprise 98% of the pens manufactured globally today.

Explaining Popular Fountain Pen Fill Mechanisms