Jewish tradition requires that certain holy items have to be written on parchment with kosher, opaque, black ink. These items are called STAM. They are books of the Torah (Sifre torah, in Hebrew), Philactaries (Tefillin in Hebrew), and Mezzuzos for the doorpost. To be kosher the ink must be made from kosher sources: plant matter, soot, water, and/or inorganic chemicals. That leaves a lot of options, and it is likely that black Sharpie would be kosher, but there are ancient recipes, and I decided to semi-follow one, but thought to use walnuts instead of the classic gall nut. I’m aiming for an ink that’s dark ,compatible with animal skin parchment, and long lasting. That is, it shouldn’t rot or degrade in moist air. Some vegetable inks rot or fade, and some iron-based inks will degrade parchment over time.

The classical recipes for STAM ink is based on using the shell of gall nuts, a tree-growth (not really a nut) found in the Mid-east. But gall nuts are not readily available in the US, so as an experiment, I’ve tried to make a respectable, kosher ink with walnuts instead. Walnut trees grow readily in the midwest. I collected a dozen walnuts with their husks from a tree near my home. The husk had been green originally, but had turned black by the time I picked them (mid November). Rather than extract the shell, I used the walnut as I found it. To extract the color, I tried boiling them in denatured alcohol, and also in water. Boiling in alcohol didn’t work well, and produced a weak ink shown below, left. Boiling in water (below right) produced a much darker liquid. I used this for the basis of my ink.

The traditional recipe begins by boiling gall nuts in water to produce a brownish ink-wash that looks hardly darker than my alcohol-wash ink. You then add soot and “green vitriol”. Perhaps that is copper sulphate, or perhaps iron sulphate. Copper sulphate is a dark blue, while iron sulphate is a light green. With gall nut water, it turns out that iron vitriol works better. It reacts with tannin to make a black color. It may also serve as a preservative, to keep mold from forming in the ink or parchment. When tried with mu walnut water, I saw no color advantage to iron vitriol, likely because the original nut water was so much darker.

I put the walnuts in a beaker as shown, nearly covering them with water, and put a piece of foil on top. The longer I simmered the darker it got, but I also evaporated water. In the end, I left the mix on a hotplate, on low, for nearly a day and got the result shown above. The ink-wash, by itself was a reasonably good ink, as shown below left. It’s darker than the ink other folks had gotten with boiled gall nuts and iron vitriol.

The traditional recipe includes three more ingredients, so I experimented with them. These are vitriol, soot, and gum Arabic. The proportions are shown below, in the form of a poem in Arabic written about 900AD (Dark Ages). The first of these additions I tested was vitriol. I first tried copper sulphate, half as much as walnut water, and found that it darkens the color a little. It also makes the combination a bit thicker thought the ink is still watery. Darkness is hardly better than the walnut water alone, but it looks OK to me. Copper sulphate is an antimicrobial, so even without changing the color, I imagined this was a worthwhile addition. I also tried adding iron sulphate. This makes the ink slightly blacker, perhaps, but not thicker, and I have less confidence about its antimicrobial properties. There were reports that iron vitriol could harm a parchment over time. I committed to tests to see if one grows lasts longer; these tests are on-going with no noticeable difference so far.

The next ingredient to add was soot. It’s used to make the ink darker, and perhaps thicker. Traditional soot is made from burning olive oil, though some folks have used wood ash. I had some soot in my lab from MER corp, a leftover from making buckminsterfullerene. I added as much soot as vitriol, as in the poem below. As expected, adding soot increased the blackness of the ink, but it also changed the texture, making it gritty and hard to write with. I had trouble dissolving the soot into the ink too, and apparently, I’m not the first to have this trouble. Some suggested heating, and some suggested honey. Heating helped, honey hardly did. Perhaps these ingredients act as emulsifiers, helping when you mix the ink. As a side experiment, I tried adding a drop of dish soap. The result, above left, was blacker than the original, but the writing is not professional grade, IMHO. The ink does not write well, and it still doesn’t cover 100%. I moved on to the next ingredient, gum Arabica.

The mixing ratios in this poem are not exactly clear. The amount of soot is the same as of vitriol, and half that of gall, but is this the weight of the gall nuts, or volume, or the weight of the dried extract, perhaps. I used volume. Even so, it’s quite a lot of soot; soot is messy and hard to dissolve.

The final ingredient is gum Arabic, the gum of the acacia tree. This seems to be used as a thickener, and my expectation was that it might also make the ink darker, and that it might help dissolve the soot. Gum Arabic is available in the US, on Amazon as an edible “candy”, so I bought some. It wasn’t expensive, but took about 10 days to get here. In the meantime, I tried honey as a thickener. It appears in some ancient recipes, but didn’t really help here, and left the page sort of sticky. Gum arabic is solider, so I hoped for for lasting product. When the Gum Arabic came, I found that it was solid, crystalline, with has hardly any taste. Maybe Arabs add sugar? I figure there might be a mystical advantage to gum Arabic since it comes from the Acacia tree, the type of tree used to make the Ark of the Covenant.

As it happens, gum Arabic doesn’t dissolve in cold water. But it did dissolve if I mixed it in, then heated and stirred for 5 minutes. The gum helped dissolve the soot too; honey seemed to help in this too, but gum Arabic seemed to do a better job. Once the gum ink dried it was nice and solid, with the dried letters standing off the page a bit; they’re raised letters, and I really like that. The ink was still sort of grainy, perhaps from the walnut bits. My understanding is that it’s kosher for STAM, but as a follow-up experiment, I’m carrying some inked parchment in my breast pocket to see if it rots or fades. So far, no change. Some samples of writing with the final product are at left. The upper words are with the iron-vitriol version (iron sulphate), the lower with the copper vitriol (copper sulphate).

Robert Buxbaum, December 22, 2024. I should mention the choice of pen. Scribes of 2000 years ago used wooden pens, as feather quills hadn’t been invented, it seems. I made a wood pen by caring a popsicle stick. This pen was used a wood for some of the samples above. The better-looking letters, and longer passages, were written with a metal, calligraphy “quill.”