insoluble precipitate

Ingredients

gum arabic, distilled water, tannic acid, ferrous sulfate, Aleppo galls, vitriol

Preparation Steps

Original Recipe Text

The experiment compared several ink types. The lab-grade ink (p. 55-56) was prepared by dissolving 0.787 grams of gum arabic in 9.2 mL of distilled water. Separately, 1.23 grams of pure lab-grade tannic acid was dissolved in 25 mL of distilled water, followed by the addition of 1.05 grams of ferrous sulfate. The gum arabic solution was then combined and stirred for 30 minutes. The Aleppo gall-based ink (p. 56) involved crushing five Aleppo galls (1.89 grams) into fine granules, which were added to 25 mL of distilled water. This solution was fermented for nine days (one set in direct sunlight, another in complete darkness). After fermentation and gravity filtration (3 hours), the solution was diluted to 25 mL, combined with a 0.787g gum arabic/9.2mL water solution, and mixed with 1.05 grams of ferrous sulfate.

Evidence

"I hypothesized that recipes made from Aleppo galls produce inks of a higher quality than those made from lab-grade tannic acid."

Remarks

The study found that gall-based inks possessed a more homogeneous nature and a richer black pigment compared to lab-grade variants, which appeared translucent and exhibited 'dark globular precipitates' (p. 57-58). Over a 41-day observation period, lab-grade ink became 'tremendously faint and practically invisible' when applied, whereas Aleppo gall-based inks maintained their quality and color intensity (p. 59-60). The author notes that the presence of tannin acylhydrolase, an enzyme produced during gall fermentation, is critical for converting gallotannic acid to the desired gallic acid necessary for quality ink production (p. 54).