ferro-tannics

Ingredients

Acacia nilotica pods, iron water, iron salts, tannins, slag, rusty metal, gum Arabic

Preparation Steps

Original Recipe Text

Tsume (or yambari) is made by collecting slag and a lump of iron and putting them into cooking pots with the fruit of a gabaruwa (Acacia nilotica). Water is poured on them and left for three or four days until it gets black, then gum Arabic is added (p. 14). Another variation involves fermenting desert date (Balanites aegyptiaca) wine until it oxidizes into vinegar, adding rusty iron pieces, and combining with soaked Acacia senegal seed pods and marua gum (p. 19).

Evidence

"A minority of inks corrode the paper substrate... The simple fermentation of Acacia nilotica pods (BL28) in iron water resulted in a ferro-tanic dye where the iron salts turned black when exposed to the tannins in the nilotica pods."

Remarks

Iron tannate dyes are known to corrode cellulose (p. 19). Heavy additions of gum are noted as a mitigation strategy to protect paper from this degradation process (p. 19).