iron-gall-inks (sample 12, sample 13) prepared according to different historical recipes

Ingredients

gum Arabic, alum, iron, gallic acid

Preparation Steps

Original Recipe Text

Two iron-gall inks were prepared. Ink 12 contained gum Arabic, whereas Ink 13 substituted gum Arabic with alum (p. 91). Alum in Ink 13 acted as an acidifying agent, lowering the pH significantly (p. 91).

Evidence

"The reason for this might be due to the presence of gum Arabic in ink 12 besides; ink 13 contained alum instead of gum Arabic."

Remarks

Sample 13 degraded more drastically than Sample 12 after ageing (p. 91). This is attributed to the fact that gum Arabic helps maintain a constant pH, whereas alum decreases the pH of the medium, accelerating cellulose degradation (p. 91). Sample 13 showed more significant changes at the 1713 and 1727 cm-1 bands (p. 91).