AIC's 53rd Annual Meeting

Preservation Programs at the National Archives and Records Administration (NARA) investigated the characteristics of iron gall ink (IGI) in low or no-oxygen environments. NARA has vast holdings of 18th,19th, and early 20th century documents with iron gall ink. With the 250th anniversary of the Declaration of Independence, conservators and scientists seek to understand more about long-term display of sensitive IGI documents. In the past, NARA has used sealed anoxic encasements for some permanently-displayed iron gall ink documents. However, recent research into IGI behavior in anoxia [1] as well as material and structural differences between the majority of paper-based documents in NARA's holdings and other treasured national records on parchment meant that the use of a low oxygen display environment needed to be examined. 

Scientist Bruce Ford previously demonstrated that fading of iron gall ink is somewhat reversible in the dark but that anoxia diminished this reversion potential. His experiments exposed ink to light levels equal to several decades of display exposure, followed by a period of darkness that allowed ink to revert overnight. We sought to conduct a similar experiment, but with a closer match between typical exposure and rest periods to exhibit conditions. Additionally, we wanted to know if IGI reversion potential could ever be exhausted or would change with past treatment history. Subsequently, we designed experiments using an automated LED MFT (2700K white LED, ~3.1Mlux) in an atypical manner. We repeatedly exposed 19th century, post U.S. Civil War era, non-record samples and paused for reversion periods in the dark on the same spot. We tracked incremental and overall change in color (ΔE00) and L*a*b* color space parameters. We also tracked and controlled temperature and humidity as much as possible to prevent movement during test periods (up to 1.5 weeks) and kept the dose for each exposure as low as possible (0.04-0.4 Mlux-hrs.), only inducing enough change required for reasonable signal to noise ratios. We performed mock de-silking and delamination treatments on historic samples to mimic the condition of many NARA holdings. Treated ink required higher dosages of light to induce the same amount of change as non-treated IGI. We conducted multiple cycles of low-dose MFT both in air and anoxia and were able to reproduce Ford’s result showing reversion in air, and significantly reduced reversion in anoxia. We investigated the nuances of reversion in each of L*, a* and b* under each condition. After several tests in anoxia, we reintroduced oxygen up to 2% concentration which showed a returned ability to revert. MFT results were also compared to an experiment with 2 klux LED lamps (up to 4.5Mlx-hrs) where no visible change was observed. This indicated reciprocal failure, however these results still have important implications for display design options for iron gall ink records.

Works Cited

1. Ford, B. 2014. “The accelerated light fading of iron gall inks in air, hypoxia and near-anoxia.” In ICOM-CC 17th Triennial Conference Preprints, Melbourne, 15–19 September 2014.