Historically, iron gall ink was traditionally made from oak galls, pomegranates, or other tannic acid-containing plant sources. You, too, can make a permanent, waterproof iron gall ink from pomegranates, just like the ancients.

Step 1: Fermenting

Materials Needed for Step 1

Pomegranates, coarsely chopped in a food processor
Distilled water
Glass jar with a lid (one large enough to hold the pomegranates and water)
Saran Wrap

Consult the chart above for the amounts of each ingredient to use throughout this Instructable, depending on the volume of ink you want to end up with. You have the choice of either using the whole pomegranate or omitting the seeds. The first time I made this, I ate the seeds and used the rest of the pomegranate for ink. The second time I made it, I included the seeds. It works either way and I didn't notice much of a color or tonal difference between the two batches.

Mix together the chopped pomegranate and distilled water in a sterile glass jar. Put on the lid and keep it on (if the lid is metal, put a Saran Wrap barrier between the lid and jar to prevent rusting). Allow it to ferment and mold over in a warm room for 2 months. The mold and fermentation will transform the tannic acid in the pomegranates to gallotannic acid, which helps to make a richer, darker ink. Don't let it ferment for longer than 2 months.

Step 2: Straining

Materials Needed for Step 2

A few layers of cheesecloth
Plastic colander (avoid metal)
Enamel or other non-reactive pot
Dishwashing gloves

Don your dishwashing gloves. Empty the contents of the jar into a colander lined with several layers of cheesecloth, over a non-reactive pot. Wring the cheesecloth to get every last drop of liquid. Discard the solids.

Note: I save the cheesecloth and reuse it for ink-making only. To launder, wash it with detergent and a little bleach and let them go through at least 2 rinse cycles (if you can still smell bleach on them, put them through another cycle). Hang them up to dry in the sun. When dry, seal them in a Ziplock bag until next time.

Step 3: Boiling to Kill the Ink Beasties

Materials Needed for Step 3

Wooden spoon
Measuring cup (one that shows ounces or milliliters)
Distilled water, if necessary

Boil the remaining liquid for 5 minutes to kill the biological activity (this is stinky, so I recommend ventilating the room). Stir as needed to prevent scorching. Allow to cool.

Pour your ink into a measuring cup and check the amount. If necessary, add additional distilled water to bring the volume back up to the original amount shown on the chart. If you have more liquid than what you started with in step 1, you can boil it down to the original level.

Step 4: Finishing Your Ink

Materials Needed for Step 4

Iron sulfate (aka copperas)
Powdered gum Arabic

Add the iron sulfate and stir well with a wooden spoon (check the chart for the amount). Your ink should magically turn black. Then add the gum Arabic (check the chart for the amount). Stir again until well dissolved. (Note: Gum Arabic will form glooey blobs in your ink. But don't worry... these will dissolve overnight.)

Step 5: Bottling & Preserving Your Ink

Materials Needed for Step 5

Several whole cloves per bottle
Amber glass bottles or Nalgene bottles
Labels

Pour your finished ink into sterile glass or Nalgene bottles. Add several whole cloves to each bottle. The cloves contain phenol and will help preserve the ink and safeguard it from mold (it also smells nice). Affix a label, one that includes the date that you made your brew.

Your bottled ink should last a few years, and even longer if you can keep air out of the bottle (transfer the ink to smaller bottles as you use it up to avoid air exposure). If you used Nalgene or clear glass bottles, I'd recommend storing them in a dark drawer when not in use, too. When your ink begins to precipitate out and drop sediment, it's no longer fit for use as a permanent ink. Make a new batch at that time.

When I first made this ink in 2011, the cost to make it was less than $2 for 32 ounces of ink, or a little over 6 cents per ounce (not including the cost of the pomegranate... I considered the peel a "recycled" ingredient).

Step 6: Make Some Writing Samples

Materials Needed for Step 6

Paper
Dip Pens
Your finished ink!

This ink is usually dark at the outset and ready to use. It may darken further as it ages in the bottle after a few weeks. Like any iron gall ink, it will go down somewhat pale initially, and then darken as it dries and oxidizes. How much it darkens and how fast it does this will depend on the type of paper you write on and the type of writing instrument you use (metal nibs will cause a chemical reaction with the acid in the ink, making it blacker). Experiment with different combinations. Test its waterproofness. Play!

Step 7: A Word About Metal Nibs

Ordinarily, traditional iron gall ink recipes such as this one are for dip pens only and not for fountain pens (see exceptions below). For the best and most stable results, use a feather quill, reed or glass pen. If your quest is maximum longevity, Dr. James Stark (a chemist and ink maker in the 1800's) warned against using metal dip pens with iron gall inks. The metal reacts negatively to the acid in the ink-- an effect that is bad for the ink, nib and paper (the nib corrodes; the ink is aged prematurely, causing it to drop sediment in the bottle you dipped from; and, you're left with marks on the page that will eat holes in the paper over time.) However, if you still wish to use metal dip pens (and you will often get a blacker ink if you do use a metal dip pen because of the chemical reaction with the metal), you can minimize these effects by doing the following:

Set aside a small amount of ink in a small glass or ceramic inkwell to dip directly from. Replenish as needed. This will prevent you from contaminating and prematurely aging the entire batch of ink.
A gold-plated or stainless steel nib will resist the corrosive effects from the acid in the ink for some time (still follow #1, even so). Other metal nibs will begin to tarnish immediately upon contact. Even taking these precautions will not ensure a stable ink on the page in the long-term, however. All iron gall inks eventually turn brown on the page, but this will happen more quickly when a metal nib is used.

Step 8: Using This Ink in Fountain Pens

Use this ink in a fountain pen at your own risk! Best results will always come from dip pens.

Technically speaking, historical recipes for iron gall inks were meant for dip pen use only and darkest results usually do occur with the dip pen. But enough time has gone by where I feel confident recommending (or not recommending) the following fountain pens with these inks. In all cases, I use designated pens and ink converters for iron gall ink use only. I do not risk using other inks in these pens for fear of a bad chemical reaction between iron gall and other residual inks. Rotring ArtPen and Pilot fountain pens in particular have fantastic ink feeds that can accommodate these inks quite well. I do not recommend using the Pilot CON-20 ink converter, however. The rubber sac does not age well with acidic inks and I've had leaking problems with them. Stick with the Pilot CON-50 converter or use the pen as an eyedropper pen if it has a plastic barrel. Most of these pens have ink/nib feeds that can be taken apart completely for cleaning. Never neglect your pen by leaving an iron gall ink in it, unused, for a long period of time.

As always, use traditional and historical ink recipes in fountain pens at your own risk! (And please notice that most of these pens are in the inexpensive range as fountain pens go.)

The best pens that require the least amount of flushing with minimal start-up hassle

Pilot 78G (use as an eyedropper pen)
Parker Vector
Pilot Varsity
Pilot Metropolitan (use the Pilot CON-50 converter, not the CON-20)
Rotring ArtPen

Pens that require regular weekly flushing, if not used daily

Pilot Parallel (use as an eyedropper pen)
Osmiroid India Ink Fountain Pen
Jinhao X450
Jinhao X750
Sheaffer No-Nonsense, early 1980's version (use as an eyedropper pen)

Pens that felt dry to write with but otherwise wrote well (and required regular flushing)

Hero 5020

Pens that required priming the next day to get them writing, but otherwise wrote wonderfully

Pilot Plumix
Noodler's Standard (non-flex) Piston-Fill
Serwix 101
Jinhao Oliver 360

Pens that did not work

Platinum Preppy (little flow)
Sheaffer Viewpoint (it writes, but quickly dries out. The lid and barrel are not airtight enough.)

Step 9: Cleaning Your Pens

Materials Needed

Distilled white vinegar
Diluted ammonia, if necessary
Toothbrush, reserved for this purpose

To clean this ink from your nibs or fountain pen: disassemble the ink feed and soak the nib and feed in diluted white distilled vinegar first before using any other kind of cleaning solution; then, if still necessary, soak in diluted ammonia. I use a toothbrush to scrub stubborn accumulations. Rinse well with water and dry. Don't forget to clean the converter (vinegar first, with repeated flushings).

I recommend designated pens and converters for this ink to avoid possible cross-contamination with other inks-- iron gall inks do not mix well with other inks, including any residual ink left in the converter or nib feed in between ink changes. Be sure your pen is thoroughly clean before filling with any iron gall ink. Don't risk ruining your pen over a bad chemical reaction!

Enjoy your ink!

For more information, see my related Instructable, Principles for Stability & Longevity of Iron Gall Inks.