What is in Fountain Pen Ink [All You Need to Know]

Ink diffusing over toy umbrella underwater

Forget about that wonderful shade of Noodler’s ink or that octagonal Montegrappa ink bottle you’re dying to open. Here we will examine what is in fountain pen ink in as much detail as conveniently possible. I don’t think I will go too far back and talk about inks from different cultures but just inks that were used and are used in fountain pens today.

Early inks (Iron gall inks)

If you own a vintage fountain pen (vintage being older than 50 years for purposes of this discussion), you might find slight traces of corrosion or wear. This usually manifests itself as a slight discoloration on the nib or in some serious cases, degradation of parts of the pen usually in contact with ink. Before you start to bemoan the lack of care the previous owner (or blame yourself) showed, this might be a bit more common than expected for older pens.

The reason for this is that iron gall ink was used when fountain pens were invented in the early 19th century and they were corrosive on metal parts. Iron gall is made primarily from iron salts like iron sulphate or iron chloride and tannic acid which is derived from the fermentation of oak galls or galls of other trees. Oak galls form when a plant responds to invasion from insects or parasitic plants like mistletoe. These are a hard wooden growth like that shown in the picture below.

Fermenting oak galls or oak apples as they are also known releases tannic acid which is then mixed with the iron salt to produce a purple-black ink. This ink would then be filtered and a binding agent (such as gum Arabic) added to it to produce ink suitable for writing. This ink has a very strong permanence and cannot be removed by erasing or rubbing it. Over time, the ink would darken to a deep purplish black which is a common color of modern day inks.

This iron gall ink is still sold and used today though not for use with fountain pens but more commonly in dip pens or brushes. Some people also prepare iron gall ink at home since all the ingredients are quite available! So if you see a bottle of bluish black ink on the shelf or for sale online don’t think of it as boring or “vanilla” now that you know there is a fair bit of thought and history behind that hue.

Modern day inks

Today’s inks have had the benefit of a better understanding of material not just of the pens themselves but the composition of inks down to the molecular level. Fountain pen inks generally contain the following ingredients:


This is always water-soluble and is used to color the ink. Eosin is a chemical compound used in red ink and it is produced when bromine is added to a fluorescent or light emitting compound called fluorescein. Now let me digress a little and mention that fluorescein actually glows when exposed to ultraviolet light. I’ll talk about it again later when I mention some interesting properties of inks.


The thickness or viscosity of fountain pen inks is important to their basic functionality. Too thick and the ink will probably not flow out of the pen. Too thin and putting the nib to paper will cause it to leak out uncontrollably thanks to capillary action. Therefore polymers are often used in modern inks to modulate the viscosity of fountain pens. A common one usually used in glycerin to adjust viscosity levels in the ink till they are just right.


Water is used as the base of fountain pen inks. This is in contrast to ballpoint pen inks which usually utilize a petrochemical. Felt-tipped pens or whiteboard markers use alcohol as a solvent hence their distinctive odor. The issue with this however is that fountain pen ink has limited permanence on paper. After the ink has dried and it comes into contact with water, it will start to run or smudge. In fact, if a mild detergent is applied to the paper, it could completely wash the writing off.

It is for this reason is that some fountain pen ink companies have special additives to their ink to ensure that they are not susceptible to this. Does this mean that the solvent used is not water? Not really. What is added is usually a chemical compound which will cause the ink to react and bind to the paper (specifically the cellulose) on a molecular level making it impossible to wash off unless you scrape a thin layer off the paper itself!

Other additives

Since the solvent used is water, there is a risk of fungal growth in the ink due to all the presence of all the organic compounds. Therefore a biocide is used to discourage this. Other interesting additives to ink include scents, shimmery ink and even glow-in-the-dark or luminescent ink. Of course all of these have to ensure that the fountain pen and the mechanisms aren’t damaged by their use.

As I mentioned earlier, I made a post with the usage of luminescent ink before. Granted it wasn’t a fountain pen but it just goes to show the virtual endless variety of inks available out there. You can find that post here which will open in a new tab.


Parting thoughts

So that is basically what is in fountain pen ink. It made me feel like going in-depth into the inks with the other interesting “ingredients’ in them but I suppose I will talk about it another time. Stay tuned for that post! Also, let me know about any ink-teresting stories you may have or your own experience with shimmery inks or those with a sheen!


About the author

Jaron is a self-confessed idealist who is passionate about fountain pens, badminton, jogging, nature and food. When not blogging, he can be found watching videos on YouTube or reading.


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