2025 Poster Session

Despite internal resistance to John James Audubon and his work, the American Philosophical Society possesses an original subscription copy of his rare double-elephant folio Birds of America (1827-1838). Each of the 435 hand-colored intaglio prints depicts North American birds at life size, and originally measured 39.5 by 28.5 inches. Thanks to the APS archives, we know the Society had its plates bound into four enormous volumes in 1840, when C. Carle & Co stab- and whip-stitched the cross-grained prints into sections for sewing over recessed cords. In 1897, after years of heavy use, the plates were trimmed, selectively lined, mended, hinged to stubs, and rebound into five volumes by the Philadelphia firm of Pawson and Nicholson. These bindings remain on the books today, and their inflexible stubs—which tend to nest together and stick that way, preventing the large, heavy volumes from opening flat—initially presented the greatest challenge for safe display.

In preparation for the APS Museum’s 2024 exhibition, Sketching Splendor, we noticed a more subtle problem. A strange purple haze obscured many of the prints' darker passages. Our efforts to diagnose the problem required consultation with colleagues in other specializations, engagement with the scientific literature, visits to sister institutions, and many rounds of testing. We discovered that the hazy material was unaffected by water and alcohols but readily removed with cosmetic sponges or white vinyl erasers, revealing saturated paint underneath. But what was it, and could we in good conscience remove it? Colleagues at Colonial Williamsburg and the Winterthur Scientific Research and Analytical Laboratory helped us to characterize samples of the material using polarized light microscopy (PLM), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy–energy dispersive spectroscopy (SEM-EDS), and gas chromatography-mass spectrometry (GCMS). Results suggested that the haze was a purely optical phenomenon resulting from desiccation of the watercolor and ink binders, which left a thin layer of loose pigment—primarily bone black—on the surface of the prints. Colleagues in paintings conservation also shared their knowledge of condition issues related to this pigment.

Developing a treatment protocol for the first volume required many more rounds of testing, followed by media consolidation on a massive scale. This challenge was compounded by the presence of ethanol-soluble gamboge and glazes throughout the Audubon prints, hydrophobic hand coloring that necessitated the use of ethanol, and managing the dwell time, viscosity, and sheen of the successful methyl cellulose consolidant mixtures. We will continue fine-tuning our approach as we treat the remaining four volumes in the series, and look forward to further collaboration with colleagues. Why this problem has developed in our copy of Birds of America and only one other, as far as we are aware, remains a mystery.