Philine Schneider. Investigation and conservation of an exemplary pieces of arsenic-contaminated historical wallpaper from the brewery Schwemme in Halle/Saale.

During the reconstruction of the baroque brewery “Brauhaus zum Pelikan” in Halle/Saale, a fragmented wallpaper from the first half of the 19th century had to be dismounted permanently. The society in charge of the brewery wanted to keep parts of this and another underlying wallpaper, both still adhered in strips to wooden slats from the former room partition, for documentation. The project initially focused on a microorganism contamination, especially dry rot (serpula lacrymans, wood-decaying fungus), scarcely studied for its impact on the decontaminated building. Investigating the fungus constituted one part of the project. However, the project’s focus turned out to be a heavy arsenic contamination that was identified via x-ray fluorescence of selected wallpaper fragments. Scanning electron microscopy of cross sections coupled with EDX allowed stratigraphic mapping: It appears that the arsenic was part of a biocide applied to the first wallpaper layer before the second wallpaper was adhered on top of it. Arsenic quantification by inductively coupled plasma mass spectrometry (ICP-MS) indicated a significant amount of toxic arsenic previously already suspected by semiquantitative colorimetric tests. The arsenic contamination determined the treatment which centered on the preservation of a small set of adjoining wallpaper strips. This involved cleaning and gluing back detached parts of the blue wallpaper in a glove box followed by mounting in a sealed frame for future display. Indispensable was the intensive and repeated exchange with experts in the field of contaminated cultural heritage that made this project possible and provides guidance for the brewery in dealing with any remaining wallpaper parts.

Presentation information: Philine Schneider, Ute Henniges, Irene Brückle, Stephanie Dietz. Thinking Outside the Box: Securing Contaminated Wallpaper Fragments. Presented at the IADA 15th Congress, October 17, 2023, iada-home.org/conference/about-the-conference/.

Philine Venus. Ammonium citrate as a washing additive for paper.

Major goals of aqueous treatment in paper conservation concern reducing unwanted discoloration and improving paper permanence. Both goals are met in most established washing treatments that involve the use of mildly alkaline (deacidification) solutions with calcium compounds. Further brightening may be achieved by bleaching, though this more invasive treatment carries the risk of cellulose damage. Lately, ammonium citrate is being used by practitioners as another method of “enhanced washing”, viewed as a more powerful brightening agent than washing and less aggressive than bleaching. However, there are few studies backed with analytical data to clarify the chemical effects of ammonium citrate on paper’s cellulosic backbone. Some publications reveal the astonishing cleaning effect, while others warn against stripping calcium carbonate from paper, compromising its stability. We designed an experiment with two historic papers and one laboratory filter paper that were immersed in solutions of 3% ammonium citrate (pH 5.5 and pH 8.5), and, for comparison, 3% citric acid (pH 2.5), ammonium hydroxide (pH 9.0), and calcium hydroxide (pH 9.0). One set of papers was washed exclusively in these solutions, the other subsequently received an alkaline reserve (calcium hydrogencarbonate). We determined the CIE L*a*b* values for all samples before and after the treatment and after accelerated aging (heat-moist aging at 80°C and 65% RH for three weeks) to capture color changes. A selection of 36 samples underwent molar mass determination by GPC-MALLS-RI.  Testing revealed clear differences between the samples in contact with citric acid and ammonium citrate compared to the other treatment solutions. Specifically: Both historic papers brightened and maintained their brightness after accelerated aging. One historic paper sample and the filter paper underwent molar mass determination (the other historic paper was already too degraded for this analysis). The molar mass data clearly indicate that both the filter paper and the historic paper degraded in the aging conditions chosen for this experiment. The other significant finding shows that deacidification following the treatments helped to maintain the molar mass of the two tested papers during the harsh aging conditions. The test treatments themselves did not cause differences on a molecular level. In conclusion, our findings show that the application of ammonium citrate may be considered as a method of enhanced washing, and the mildly acid variant (pH 5.5) brightens the papers tested in our study without compromising its molecular integrity as long as the treatment solution is thoroughly washed out and an alkaline reserve is added. We noted that, as with other washing treatments, the hue of the treated papers changed and this color change should be taken into consideration. For long-term stability, it is crucial to rinse the treated papers and remove the substances used for enhanced washing and to add an alkaline reserve.

Presentation information: Philine Venus, Ute Henniges, Irene Brückle, Crystal Maitland, Theresa J. Smith, Antje Potthast. Ammonium citrate for enhanced washing of paper. Presented at the 51st Anual Meeting of the American Institute for Conservation, Jacksonville, Florida, May 18, 2023; aic51stannualmeeting2023.sched.com/book-and-paper-ammonium-citrate-as-a-washing-additive-for-paper.