Oak Gall Ink - a more in depth look

As you start to read this, think for a moment what it is about reading and writing that is so captivating. Why do we as a race write? The answer to that question is as complex as it is fundamental. Knowledge is power. And writing stores knowledge. Today we have digital movies and pictures that store knowledge for us as well as magnetic disks and the like. We, as a species, have come a long way from piling rocks a certain way, to painting rocks and caves, to carving clay tablets and writing with ink.

When we started to write on some kind of storable surface the human race really made its first leaps forward, after learning how to tame fire and use the wheel. Writing allowed people to learn from people they had never met and could never meet. It stores knowledge for others to learn from so people didn’t have to reinvent things. Ink made it possible to store more information, in less space with less effort than chiseling rock and pressing clay tablets. Parchment and paper are written on with ink which stores better, more easily and more efficiently. It is much easier to write on and is much more portable than clay, cave walls, and stones.

There are many kinds of ink used today, in the time period we study of the pre-1600 world there were two major types of black ink; Lamp Black and Oak Gall Ink. We will be looking at Oak Gall Ink. Ink by it's very nature is both creative and utilitarian. Today we take ink for granted but the reality is that ink has the almost mystical ability to store knowledge and be art at the same time. The process of making ink is also very creative. One testament to that is that there are literally hundreds of recipes for making Oak Gall Ink and getting the balance right for what you want isn't just a simple process of throwing things together. You have to be creative in your approach and be on your toes during the process itself.

Where Does the Work “Ink” Come From?

It comes from Middle English enke, from Anglo-French encre, enke, from Late Latin encaustum, from neuter of Latin encaustus burned in, from Greek enkaustos, verbal of enkaiein to burn in.[1]

This is the same root word that the word “caustic” come from which is another way to say acidic. Oak Gall ink “bites” or burns in to the surface it is written upon.

What is ink? Why isn't it considered a paint or a dye?

Dyes fundamentally change the material they come in contact with, in other words, dyes stain things. Paints on the other hand sit on top of whatever surface they are on and do very little to that surface except cling to it. Inks do a little of both making it an intermediary liquid. Ink bites, or burns, into the surface it is on and it stays on top of that same surface. It is the ingredients of ink that give it these properties.

Ink by it's very nature is creative. These days we take ink for granted but we really shouldn't. Ink has the almost mystical ability to both store knowledge and be pretty at the same time. And if it wasn't for the creative making of ink and use of ink we wouldn't know very much about the world that came around before electronic letters were used. In fact it likely would have taken us a lot longer to get to where we are today then it did. So not only is ink creative by nature, but by it's very nature it helps other things to be creative as well.

What are the ingredients of Oak Gall ink?

There are a lot of recipes for Oak Gall ink out there and lots of different things you can use to make oak gall ink. There are however, four basic ingredients:

1 - Oak Galls (which have tannic acid),

2 - Copperas which is chemically known as Ferrous(II) Sulfate

3 – Water (preferred by me), also usable, wines and brandies.

4 - Binder (I prefer Gum Arabic).

Oak galls contain tannic acid. This tannic acid is leached from the oak galls by soaking or boiling them in a liquid. I used water though some recipes call for the use of an alcoholic liquid such as wines.

Ferrous Sulfate in period was called different names. The most common appear to be: Copperas and Green Vitriol. Ferrous Sulfate comes in two forms. One is a moist blue-green odorless crystal and the other is a white powder form. The blue-green odorless crystal has 7 H2O molecules attached to it. It was believed that because it is greenish in color that it had copper in it. However, one of the ways ferrous sulfate was made by first pouring water over sulfurous earth and then pouring that solution over iron such as nails and spent filings. Green Vitriol is a name used to differentiate it from Blue Vitriol which does contain copper. For this project I used the white powder form.

Isn’t oak gall ink bad for writing with because it is acidic?

This is a common question about Oak Gall ink. Observation and common sense both confirm and deny this. It is absolutely true that that this ink has been known to create holes in parchment destroying the pages it is on. The Vatican Librarian called the conference of St. Gall in 1898 to determine how to better preserve ancient manuscripts. One of the topics was about the corrosive qualities of oak gall ink.[2]

One must also realize that there are literally thousands of manuscripts out there written with this very kind of ink that have no damage to them whatsoever. So there must be, and are, several factors coming together to cause the problem, it isn’t just the ink. And it takes the ink several centuries to cause problems if any. I will revisit this later in the paper.

One of the ways to decrease the acidity of oak gall ink is to add in crushed eggshells. Eggshells contain Calcium Carbonate which is a base.[3] Mixing an acid and a base together causes them to become more neutral of pH of 7 which is preferred.

How my ink was made


1 gallon steam distilled water 40 grams Aleppo Oak Galls

9 grams Ferrous Sulfate 5 grams crushed egg shells

Gum Arabic (amount varies)

By weight 4.369% of this ink is solids. This ink is 95.631% by weight is made of water.[4] (see figure 1)

Materials explanation:

I use distilled water as tap water and modern day rain water have chemicals in them that would almost certainly not have been found in the rain water in period. The ferrous sulfate that I use is lab quality as it was the cheapest and easiest to procure. The Aleppo Oak Galls were ordered from John Neal Bookseller. The eggs I used were modern eggs from the grocery store. I plan to acquire some period eggs in the future and see what if any effect they have on the final result. The Gum Arabic was ordered from Kremer Pigments.


In a well ventilated area, I put the distilled water in a metal pot to boil on a modern stove. I have used a wood fired set up before and find that besides taking three hours to boil outdoors and 20 minutes to boil indoors there is no appreciable difference in the results. While waiting for the water to boil, I broke up the oak galls in a mortar and pestle down to rice sized pieces. Once the water came to a boil, I added the broken oak gall pieces (and powder) to the water. This process leaches out the tannic acid from the oak galls.

I then used a separate mortar and pestle to grind up the egg shells. I used separate mortar and pestle because egg shells are a base while the oak galls contain acid and I don’t want to adulterate the leaching process from the oak galls. I find no documentation to do this in period documents, but find plenty of warnings to do this from later resources. I will test out the difference when I can afford a third mortar and pestle.

When the water turns a dark brown, similar to that of good strong coffee, there is also an earthy acrid smell that comes with it. Thus the need for a well ventilated area. I have put my face over the boiling pot and smelled. This is a very unpleasant experience though it is not harmful.

I then added in the Ferrous Sulfate (copperas) to the solution and it immediately turns black. At this point I have created a dye. This dye, I have been told by Mistress Eithne of the Barony of Jaravellir, can be used in dyeing fabrics. The smell changes somewhat in nature to a less earthy scent though it is still acrid. I gently stir the solution with a wooden fork to make sure that the chemical reactions are happening as much as possible. I use a wooden fork because it is long, reusable, cheap, non-reactive and close to period using a wooden spoon.

Acidity revisited and how to deal with it.

Having tested this solution in previous batches using calibrated lab equipment I have found the pH to be around 5. This is roughly the same level of acidity you find in regular rain water today.

It would be very easy to make the solution more acidic simply by adding more oak galls and/or adding more ferrous sulfate. Many recipes from in period call for more ferrous sulfate than I used. The lowest pH I have ever found when testing it with the calibrated lab equipment was 2.8. 2.8 on the pH scale is somewhere between vinegar and soda or lemon juice and orange juice.

To temper the ink, or neutralize it, I add in the egg shells after I put in the ferrous sulfate. Again, it is important to put this in after the Tannic Acid and Ferrous Sulfate reaction occurs. The chemistry would change dramatically. After putting in the egg shells the pH moves toward the neutral 7 which would be ideal. Having tested this solution previously with the same calibrated lab equipment I find the pH to be around 5.5 to 6. A pH of 6 is roughly the same as saliva, cow milk and egg yolks and is less acidic than rainwater today. When the egg shells are dropped in, they dissolve and a precipitate floats to the surface.

Precipitates are common in acid base reactions and are a form of salt. I have not been able to determine what this precipitate is exactly though one can determine from comparison that it is not simply egg grinding floating to the surface. I take out the precipitate as it could clog the pen while writing.

Getting out the leftover solids:

Once the solution has cooled to lukewarm, I do a two step filtering process. The first filter is actually just a strain. I strained this ink through a metal strainer. I have strained it through cheese cloth previously and have found no appreciable difference in the outcome and the metal strainers can be reused whereas the cheesecloth can not be. This straining gets the larger particles out.

The second step is to filter it through coffee filters. I have filtered through sponges as well as tightly hand woven fabric as may have been done in period. I have found no appreciable difference in the quality of the ink when using coffee filters. Coffee filters are cheap and disposable and like the sponge and fabric, are pretty much one use items for this purpose. The ink is then filtered into a clean container. I used the bottle that had held the distilled water. This is how I store the dye before it gets bottled.

Gum Arabic (the binder) is added making it ink:

I bottle the dye and then I then add liquid Gum Arabic. Adding the Gum Arabic any sooner would only clog the strainer and the filter. I have done that previously and it did have an affect upon the quality of the ink in a very negative manner. Further, it made straining and filtering a very difficult experience. I add the Gum Arabic after bottling the ink because not all uses of ink call for the same amount of Gum Arabic.

Gum Arabic directly affects the flow of the ink from the pen to the writing surface as well as having a direct affect of how the ink interacts with the writing surface. The larger the amount of Gum Arabic the greater the surface tension of the ink will be. The ink will also be a thicker ink. What amount is desirable is based entirely on how you will be using the ink. More gum arabic for slanted surfaces and quills and less gum arabic for metal nibs and flat surfaces. For this ink I put in the amount of Gum Arabic I find most useful for use with a metal nib on a level surface.

Things to think about when adding Gum Arabic:

The material and surface of you pen as well as how it is made directly contributes to the flow of ink from the pen to the writing surface. If you write with a metal dip pen, the ink goes from your pen to the writing surface through the capillary action of the cracks in the metal of the dip pen. It is a very well engineered process that pulls the ink slowly to beneath the pen tip. If you write with a feather quill the ink travels down the feather shaft very quickly. If you write with a feather quill and have removed the top layer from the feather shaft the ink will travel more slowly to the tip of the pen but more quickly than if it were a metal nib.

The angle at which one writes has a direct effect on how gravity will act upon the ink. When you write with your pen perpendicular to the surface of the ground, the ink will be drawn out of your pen very efficiently by gravity. Ink will be pulled out of the pen with varying degrees of less efficiency the flatter you angle becomes. Writing on a scribal desk of 45 degrees causes your pen to go to a flatter angle. Writing on a scribal desk of 60 degrees causes an almost flat angle of your pen to occur.

When writing on a level surface, the ink only takes up as much space on the writing surface as its surface tension allows. When writing on angled surface your ink will tend to pool and run toward the portion of the writing surface closes to the ground. The more extreme the angle, the more gravity will affect the ink once on the writing surface.

The writing surface itself also affects the ink. Parchment and vellum that is well polished and prepped is a dream to write on. It isn’t hairy, coarse or fibrous enough to draw the ink into spidering or cause other problems. Paper can cause spidering simply because of how it is made.

As we can see there are a lot of factors that affect how ink interacts with the pen and the paper. I put in the amount of Gum Arabic to fit the set of circumstances most likely to occur. If you write on flat surface with a quill on fibrous paper you are going to need a significant amount of Gum Arabic. If you write on a 60 degree scribal desk with a metal dib nib on manuscript quality vellum you will need very little Gum Arabic. I prefer to put in the amount of Gum Arabic for what is most likely to occur. That is best done after bottling the ink.

Why does it go on kind of grey?

This ink has some very peculiar qualities to it that are very good. This ink turns black when exposed to oxygen. That occurs because the iron in the ink is oxidizing similarly to how a caste iron skillet oxidizes this is a healthy and protective form of oxidization for iron. Also this ink is photo reactive meaning that it reacts when photons hit it. It actually turns blacker in light. So this ink is not only lightfast and colorfast but it is helped along, to a point, by the light.

Over time this ink turns black. It has been my experience that newly made batches of ink turn black more slowly than older batches of ink. One way to overcome this is to burn a small scrap of parchment or paper or wood, grind up the char that remains and add it to the ink. Using this form of carbon as an additive was very period.

After a few hundred to more than a thousand years, the reactions from oxygen will create a new form of oxidization. It starts to turn reddish or faint brown. This is the form of oxidization we don’t like to see on iron metals and in normal terms we call it rust.

How Period is This Ink?

That is a very sticky question to answer. Let us start with the basics. The recipe follows the pattern of period ink recipes but is not directly a period ink recipe, I made up this recipe myself. The materials are as period as I can get them to be. None of them are directly or immediately harmful to someone. Though copperas will cause constipation (you can get a prescription for it,) and are used as mild herbicides (used in many gardening products,) it isn't as bad as the mercury and arsenic that are in some period pigment recipes. Don’t go drinking this stuff but if it gets on your hands, you will get stained hands for a bit but as long as you wash it off relatively soon, you're fine.

I have made very period ink however, the number one ingredient, water, is impossible for me to get a period version of. Water is 95% of the ink (See Figure 1 below) and chemically it is simply impossible for me to get water that is chemically similar to the water that would have been used in period. Some recipes call for using rain water. Rain water today is chemically very different from rain water in period as we have added a lot of chemicals to our atmosphere. Some recipes call for using water from a clean clear swift running stream. We have added a lot of chemical pollutants to our streams just the same way we did to our atmosphere. And when we consider that water is a key ingredient in making the oak galls and the ferrous sulfate, well, we can see that it is impossible to make ink in a completely period fashion. The ingredients are as period as I can get them to be. They were put together in a period fashion using either period techniques or modern techniques that save money but may have a negligible affect on the outcome of the quality of the ink.

What are some other things to think about?

There is also chemistry that is occurring between the ink and chemicals used in making parchment. The process of making animal skin parchment used slaked lime AKA calcium carbonate. Calcium Carbonate is a base.

The writing surface of vellum is often additionally prepped by the calligrapher with pounce which is made up of pumice and cuttlefish bones. Pumice itself is chemically inert meaning it does not chemically interact. However cuttlefish bone is made up of Calcium Carbonate which as is already known is a base.

The ink, as we know, is acidic. It can have a pH of between 2.8 and 5.5. We also know that acids and bases when mixed rush toward the neutral pH of 7. The following questions I have no answers to but often ask myself and hope to someday find an answer to them. To what extent do the ink and the pounce and the vellum neutralize one another? How much does the Gum Arabic or other binder inhibit that reaction? How much of the reaction occurs at all? What affect does that have on the storage of the manuscript over time? How does that affect the ink eating into or not eating into the parchment or vellum? Is this why ink and parchment making recipes vary so greatly from area to area? If the water is so different what was the pH of the water in period and from what sources and places? Where did they get their oak galls? How did they make their copperas?


Writing stores knowledge and ink made this process quicker to do and easier to store. Oak gall ink was by far the favored ink of choice in Europe for more than a thousand years. This Oak gall ink is comprised of four basic ingredients on average Oak Galls (which have tannic acid in them), Copperas (ferrous sulfate), Water, and Gum Arabic. The amount of Gum Arabic used should be titrated to meet the specific ways, materials and the ways the calligrapher writes. This recipe is a period fashioned recipe and the materials are as period as possible.


Figure 1

An analysis of the ink by weight:

Below is how this recipe works out by weight:

1 gallon = 3.8 liters (l)

1 liter = 1,000 milliliters (ml)

1 ml water = 1 gram (g) (at sea level and 1 atmosphere of pressure)

Which means: 1 gallon of water = 3,800 grams

24 grams tannic acid.

9 grams Copperas.

33 grams solids for the dye.

33 grams solids/3,800 g water = 0.008684 or 0.8684% of the dye is solids (excluding gum Arabic binder and egg shells)

Gum Arabic is a binder that I add in after the fact titrated to need. So the amount of gum Arabic solid put into the ink varies. For use with metal dip pens used on a flat surface about 128 grams per gallon of ink.

Egg shells are put in to temper the ink and at most weigh in at 5 grams.

So total weight solids is = 24g tannic acid + 9g copperas + 5g eggshells + 128g gum Arabic = 166g solids.

166g solids/3,800g water = 0.04368 or 4.368% of ink is solids by weight.

That means that this ink is 95.631% by weight is made of water.


[1] Merriam-Webster online dictionary 2/19/2011 http://www.merriam-webster.com/dictionary/ink

[2] Minutes of the St Gall Conference 4/1/2011 http://cool.conservation-us.org/byorg/abbey/an/an22/an22-7/an22-702.html

[3] “Concepts of Eggshell Quality,” Dr. Gary D. Butcher, Dr. Richard D. Miles http://www.afn.org/~poultry/flkman4.htm

“A Booke of Secrets” Written first in Italian, and now newly translated into English by W.P., London, Printed by Adam Islip for Edward White, and are to be sold at his shop at the little north door of Pauls at the sign of the Gun. 1596

“Iron Gall Ink Website” http://www.irongallink.org/

Solutions for Treating Iron-Gall Ink Artifacts By Sylvia Albro and Julie Briggs Library of Congress http://www.loc.gov/loc/lcib/0806/conservation.html

Old Ink Recipes – Evan Lindquist http://www.evanlindquist.com/oldinkrecipes.html

The Tea Man 2/19/2011 http://www.teatalk.com/science/tannin.htm

The Scriptorium http://www.thescriptorium.co.uk/showfactpdf.php?linkpage=ink

E-mail Correspondence, David Roland to The British Museum January 24, 2007 responded February 15, 2007. “An Inquiry into ink on manuscripts (Public Enquiry no 69)”

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