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Making pigments from local materials (2): oak galls

On Friday we drove the southwestern flanks of the Santa Rita Mountains to the hamlet of Patagonia ~ we stayed roughly above 4,000 feet elevation, and I had plenty of opportunity to look for oak galls to try the recipe for oak gall pigment in Gwen Diehn's Decorated Journal. Oak galls are the leftover baby wasp 'housings'; worldwide there are thousands of tiny wasp species (some no bigger than the nib on a pen), which are obligate to one species of oak. On this oak they inject a hormone that triggers the oak to form this structure . . . in which the wasp lays its eggs, which then develop, nicely protected, in the gall. Some are tiny, some are large. All are produced entirely by the plant, and are tannin-rich (and thus can produce nice inks and pigments; galls in Europe have been used for centuries as inks; tannins also are used for curing leather ~ the origin of "tanning"). The holes in the galls indicate where the young wasps emerge.

I finally found some nice big ones, on a Mexican gray oak (Quercus grisea), and collected five.

Back home, I followed the Medieval recipe: 

Grind the galls to powder ~

Boil them in rainwater for as long as it takes to recite the Pater Noster three times ~

Add drops of a mild acid (vinegar or lemon juice) until the liquid turns from rich brown to deep black.

Results are inconclusive as well as enticing. While the majority of the liquid never turned beyond a rich, reddish brown (see the leaves in the drawing above, of the oak galls ~ these are painted with the gall pigment; the oaks there were very stressed, with dried leaves; did this contribute to tannin-poor galls?), I laid down a silver-plated spoon, on which were bits of the ground gall and liquid, on the counter; half an hour later, a tiny puddle under the spoon was a rich, dark black. I tried many other experiments - boiling further (to reduce), adding more lemon, adding vinegar, but was never able to reproduce that one teeny black smudge.

So, my experiments will continue  . . .

1 comment:

  1. During my research so far today, I've learned that you need to add iron to your gall inks. Iron supplement tablets or soaking rusty bits in a vinegar-water solution


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