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Fountain Pen 101: Ink Reservoirs

Posted in Fountain Pens

Last week I covered ink, this week I’m covering it’s holders, namely ink reservoirs. The reservoir is what makes a fountain pen a fountain pen. Without one, it would be a dip pen. Essentially, there are two categories of ink reservoirs: removable and built-in.

The ratings you’ll find below are averages and based on my opinions. Each pen is different, and every person has different preferences, so don’t discount a pen just because of a rating; research it first. Ink capacity is rated ★☆☆☆☆ (least capacity) to ★★★★★ (most). Ease of cleaning is specifically for cleaning the reservoir itself, not the entire pen, and is assuming you do not disassemble the pen at all (e.g. removing the nib unit).

If you want video instructions or step-by-step photo instructions of how to utilize some of these ink reservoirs, check out these guides: JetPens | Goulet Pens

Removable Reservoirs


Capacity ★★☆☆☆ | Cleaning N/A

Photo from

These are pre-filled, disposable tubes. You won’t find the diversity of ink brands and colors in cartridge form that you find in bottles, but they make for easy travelling. Cartridges can be refilled, if you want, but generally only last through a few uses since the plastic that connects to the feed isn’t very sturdy. Cartridges are made to be disposed of after use, and, as they degrade, you’ll find that they start to leak.

Use guides: JetPens | Goulet Pens


Capacity ★★☆☆☆ | Cleaning ★★★★★


These are basically, empty, reusable cartridges. You can fill them with any ink in one of two ways. You can either install the converter empty, dip the nib in ink, and engage the filling mechanism (squeeze, button, or twist depending on the converter), or you can fill the converter with a syringe (my personal favorite) then install it and scribble a bit to get the ink flowing.

I know there are plenty of people who prefer the “dip and fill” method because the nib is instantly ready to write, but I don’t like the mess. And, if you’re using a twist-fill converter, you just need to twist it up a bit to force ink down to the nib.

Use guides: JetPens

Cartridge & Converter Compatibility


Capacity ★★★★★ | Cleaning ★★★★☆

Eyedropper Conversion
Photo from

This is an in-between ink reservoir. It’s not removable, but it’s not exactly built-in. Converting a pen to eyedropper fill means you’re utilizing either silicone grease, o-rings, or both to make the pen airtight so you can fill the entire body of the pin with ink. A quick Google search will yield easy conversion instructions, and you can find the supplies on Amazon, most pen store websites, and at your local hardware store. Eyedropper conversions are especially useful with flexible nibs (like the Regalia Writing Labs nibs I mentioned a couple posts back) that lay down a lot of ink because of the high ink capacity.

Conversion guides: JetPens | Pen Chalet


In researching ink reservoirs for this post, I discovered that there are three types of built-in reservoirs: piston, vacuum, and sac. I won’t go into detail about all the filling systems contained within these categories, partly because some of them are somewhat rare, and partly because they’re just variations of the main type.


Capacity ★★★★★ | Cleaning ★☆☆☆☆

Piston Fill Pen
Photo from Most Wanted Pens

Piston ink reservoirs are fairly common. You’ll find them in many TWSBI pens. Basically, a piston ink reservoir has something you twist (usually a knob at the butt end of the pen) to move the interior plunger up and down to empty and fill the pen. If your piston pen has a nib unit that can be unscrewed, it’s much easier (in my opinion) to remove the nib and clean or fill the reservoir using a syringe.

Filling Guide: Pen Chalet


Capacity ★★★★☆ | Cleaning ★★★☆☆

Vacuum Fill Pen
Photo from Pencil Case Blog

Vacuum ink reservoirs are varied. You may find pens listed as “power-filler”, “draw-filler”, pump, etc. but they all “do” the same thing. A mechanism in the pen creates a vacuum to draw ink into the reservoir. With some vacuum fillers, the filling mechanism is a bit counter-intuitive. Take my Visconti Homo Sapiens, for example: you pull out the “plunger” (for lack of anything else to call it) to vacate the ink, then push it back in to create a vacuum which draws ink into the reservoir once the “plunger” is completely pressed back into the body.

Some vacuum fillers require the knob of the plunger to be unscrewed when writing. Check out this post from Goulet Pen Co. for more information.


Capacity ★★★☆☆ | Cleaning ★★☆☆☆

Sac Pen
Photo from Pen Trace

Sac reservoirs were popular in vintage pens, but they can still be found in modern pens (e.g. Conklin Mark Twain Crescent). Don’t confuse a sac-based reservoir with a bulb filler. Bulb-fillers utilize a small sac to create the vacuum to fill the pen’s reservoir. In a sac pen, the sac itself is depressed and filled with ink. This can be done by means of an external depression system (crescent, lever, coin, etc.) or by depressing the sac manually.

There are a few other ink reservoir systems, but they are either uncommon, or specific to vintage pens And I know next to nothing about them. 😉

Ultimately, I prefer cartridge/converter pens because I feel they’re easiest to clean, and you always have a way to check on ink levels. I also enjoy the lower ink capacity because I like changing inks often.

It’s worth testing out the pens of various ink reservoir types if you wan. Borrow pens from friends, or watch videos to familiarize yourself with the pen and its filling system, especially how to clean it. Cleaning is an integral part of owning a fountain pen, and if you hate cleaning your pen, you’ll likely dislike the pen itself. More on cleaning next week. 🙂

One Comment

  1. Eyedropper pens are fairly popular in India, and a number of makers provide them. They vary from a bit slim and small, like the Noodler’s Charlie (included free with most of their 4.5oz bottles of ink) and Fountain Pen Revolution Muft (one included free with orders over $25), to the almost absurdly huge and expensive Guider Super Zimbo.

    April 19, 2020

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