The proper name is “oak galls ” or “gall nuts”, but tree pearls describes very well what they are: a tiny (harmless) wasp lays its eggs inside the bark of oak trees, and the tree in reaction generates a ball of solid, tannin-rich wood around the intruder. These start showing up in summer and for thousands of years have been one of the best-known sources of making ink. This was still the case up to WW2, so it’s remarkable that they’ve been so completely forgotten.
All of the galls above came from a single, unhappy oak no taller than I am (unhappy because it grew beside a busy road and was never going to be healthy, which probably made it more vulnerable. Also, it was too small to put out acorns, and I think that’s a factor because a large oak busy growing acorns has little energy to spare to make gall nuts). I spotted them while they were still green, and returned to harvest them weeks later, when they would have browned and a hole appeared, signaling that the wasp had hatched safely! In case I pick up an unhatched one, I leave the lot in a bowl by the window for a few weeks, so any hatchlings can escape. They are very cute and well-mannered, so their brief presence in my kitchen doesn’t bother me at all.
When I was ready to make some ink, I pounded all my galls roughly, just to break them up a bit, and then placed them in water to soak for at least a week. A faster way of working is to grind them to dust and then boil them, but why consume energy if there’s no rush? This is an exercise in sustainability. After only two hours the water already looked like this:
A week or so of daily stirring later, I strained out the solids and ended up with a pure tannin solution. This has uses of its own, so I set some aside, and prepared to turn the rest into calligraphy ink.
One might ask, since this is about the tannin, can’t the same result be attained with acorns? Apparently, acorns can achieve a good result, but the tannin is more concentrated in the galls. Also and more importantly, acorns are the oak’s progeny as well as food for a multitude of forest creatures. It’s not right to seize that for our own purposes when the galls are sitting there useless to beast or tree once the wasp has hatched. If left alone, they don’t fall off but slowly decompose on the branch. Even a handful of galls will yield enough ink to last any calligrapher until the next season.
The next step in making the ink is adding an iron mordant, which instantly turns the solution a deep black. Then, for it to be a usable ink, I added gum arabic (pounded from the crystals below and dissolved in warm water).
Now I’m experimenting with different amounts of it, and also with adding a little honey to make it even thicker. Too much gum arabic can make the ink flaky when it dries, but this hasn’t happened so far, probably because I’m working on paper, which absorbs the ink. The real test would be vellum, which was the original surface for this ink, and I have a scrap somewhere so now’s a good time to unearth it.