Interactions in iron gall inks

Abstract

Simple iron gall inks composed of gallic acid, ferrous sulfate, and gum arabic and in some cases also of copper(II) sulfate were prepared. The process of iron ion complex formation with gallic acid was investigated using UV-VIS spectroscopy, pH measurements, and by monitoring the concentration changes of Fe(II) ions. The admixture of Fe(II) ions to gallic acid induced a bathochromic shift of absorption bands at 215 nm and 265 nm in the UV-VIS spectra. Formation of a new absorbance band in the visible area was also observed and used to calculate the initial rate of complex formation. Concurrently, the pH values and the concentration of Fe(II) ions in the solution decreased. Gum arabic significantly enhanced the complex formation and its stability. On the contrary, the addition of Cu(II) ions to the solution decelerated the complex formation considerably.

Mahi:A Unique Traditional Herbal Ink of Early Assam

“…Quantitative estimation showed the presence of small amounts of GA compared to EG, with QC showing maximum value. Figure 3 shows the UV-visible spectra of M2 along with those spectra of its constituent polyphenols and their complexes with iron 6 . A flat absorbance of M2 in the visible region can be observed as expected from the black colour of the ink.…”

“…A carbon-based ink, Mashi, was popular in ancient India, except in the eastern part, especially Assam, where an herbal counterpart, called Mahi, was popular till early 20th century AD 5 . An herbal ink, known as gallotannate and iron gall ink (IGI), was widely used in Europe since ancient times till the late 20th century AD 6 . The major ingredients of IGI were tree galls, green vitriol or copperas, gum arabic and water; wine, beer, vinegar and boric acid were also used 6 .…”

“…An herbal ink, known as gallotannate and iron gall ink (IGI), was widely used in Europe since ancient times till the late 20th century AD 6 . The major ingredients of IGI were tree galls, green vitriol or copperas, gum arabic and water; wine, beer, vinegar and boric acid were also used 6 . A very low pH and excess iron of IGI degraded manuscripts written on paper through acid hydrolysis of the glycosidic bond and through hydroxyl radicals 4,6 .…”

“…The observed surface-active nature of Mahi can be attributed to glycosidic biosurfactants, viz. saponins, which act as solubilizer, stabilizer and binder in Mahi like the gum arabic or animal glue counterparts in other contemporary inks 4,6 . The total phenolic content in the water extract of lyophilized M2 was found to be 179.8  2.5 g gallic acid equivalents per gram of lyophilized sample (g GAE/g) from FolinCiocalteau method using gallic acid as the standard 17 .…”

“…The major ingredients of IGI were tree galls, green vitriol or copperas, gum arabic and water; wine, beer, vinegar and boric acid were also used 6 . A very low pH and excess iron of IGI degraded manuscripts written on paper through acid hydrolysis of the glycosidic bond and through hydroxyl radicals 4,6 . On the other hand, the nondestructive nature of Mahi is proven by tens of thousands of centuries old Sancipat 7 (a cellulosic folios made of bark of sanci tree, Aquilaria agallocha) manuscripts, a testimony of the rich literary and socio-cultural heritage, still existing in Assam without losing the glaze of the ink ( Figure 1 and Figure S1 (see Supplementary Information online)) 8 .…”