J.CAC VOLUME 37 (2012)
A Comparison of Aqueous versus Ethanol Modified Calcium Phytate Solutions for the Treatment of Iron Gall Ink Inscribed Paper
While the calcium phytate/calcium bicarbonate treatment has proven to be effective in delaying iron gall ink corrosion on paper, this aqueous treatment cannot be used safely on documents with water soluble iron gall inks. This study explores the efficacy of ethanol diluted calcium phytate. Laboratory prepared iron gall ink with excess iron ions was applied to a nineteenth century ledger paper to create samples that were then treated with six variations of calcium phytate solution with and without ethanol modification, and with and without alkaline washing. They were subjected to accelerated heat aging at 90°C for 14 days. The unaged control and aged samples were tested with bathophenanthroline iron (II) test papers, zero-span tensile strength, pH and colour measurements, and inductively coupled plasma atomic emission spectrometry (ICP-AES) multi-element scan. Results after heat aging showed that all variations of phytate solution, without further deacidification, were able to reduce the loss of strength in paper with and without ink. Treatment with undiluted phytate (100%) with or without alkaline washing offered the best protection. Inks without alkaline washing retained more iron ions in the ink and as a result retained more phytate. Dilution of the aqueous phytate solutions with ethanol reduced its ability to remove acids, hence reducing its ability to protect paper from strength loss. Repeated applications of the ethanol modified solutions resulted in the accumulation of more phytate on the paper and ink, and delayed the recurrence of iron (II) ions.
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