iron-gall-ink

Ingredients

gallic acid, ferrous sulphate, copper (II) sulphate, saffron, gum Arabic, alum, NaCl, oak galls

Preparation Steps

Original Recipe Text

The iron-gall inks were prepared in seven groups to test different parameters. Group 1 studied iron to gallic acid mole ratios: 0.17 (ink 3), 1.5 (ink 2), and 3.6 (ink 1) (p. 52). Group 2 investigated copper to iron mole ratios: 0.01 (ink 6), 0.4 (ink 4), and 0.8 (ink 5) (p. 55). Group 3 examined saffron to iron weight ratios: 0.03 (ink 11), 0.17 (ink 9), and 1 (ink 10) (p. 57). Group 4 combined copper and saffron (p. 59). Group 5 used historical recipes: ink 12 contained gum Arabic, while ink 13 used oak galls instead of gallic acid and contained KAl(SO4)2.12H2O, NaCl, and gum Arabic (p. 61).

Evidence

"In groups 1, 2, 5 and 6 considerable color changes were observed after ageing. This change may be attributed to the increase in the oxygen containing groups such as carbonyls and carboxylic acid formed in the cellulose due to degradation."

Remarks

UV-Vis spectra of iron-gall complexes exhibited wide maxima between 560 and 600 nm (p. 52). Maximum absorbance and wavelength increase as the Fe/Ga ratio increases (p. 55). In Group 5, the presence of alum in ink 13 may act as an acidifying agent, while gum Arabic in ink 12 helps adjust and stabilize the pH (p. 61). The darkening of samples after ageing is quantified by a decrease in L* values, likely due to the formation of degradation products like purpurogallin and ellagic acid (p. 66).