AIC's 53rd Annual Meeting

Recently, the National Archives and Records Administration (NARA) announced an intention to permanently display the Emancipation Proclamation (EP) to tell a more complete story of the nation’s road toward a more perfect union. The EP is a double-sided document with iron gall ink (IGI) on paper, as well as an original seal and silk ribbon remnants that once held the document as a folio. Its treatment and display history are complex and have resulted in variations in text density and substrate appearance across pages. To determine the exhibition specifications for this iconic document, NARA scientists and conservators engaged in intensive investigation to identify and reduce risks of long-term display. In the past, NARA has used sealed anoxic encasements for documents permanently displayed. However, recent research into IGI behavior in anoxia1 as well as material and structural differences between the EP and other treasured national records meant that the use of a low oxygen environment needed to be examined for the unique needs of this document. 

Scientist Bruce Ford previously demonstrated that IGI fading can revert in the dark, similar to Prussian blue, but that anoxia diminished this reversion potential. His experiments exposed ink to light levels equal to several decades of display 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 contemporaneous non-record samples and paused for reversion periods in the dark on the same spot, tracking the within test as well as overall change in color (ΔE00) and L*a*b* color space parameters. We 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 the EP. Treated ink required higher dosages 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 both reversion in air, but 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 requirements for the EP and other IGI 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.