Examining the Use of Ozone Test Strips to Detect PVC Plastics in Museums

Mary Coughlin, Gwénaëlle Kavich, G. Asher Newsome, and Qiuhui Wang

Abstract

For the past 80 years, Poly(vinyl chloride) or PVC has been one of the most commonly used plastics in the world. PVC’s popularity means that it is found in the vast majority of museum whether as works of art, examples of contemporary material culture, or as storage and exhibition products. As some PVC degrades, plasticizer migration and/or the release of acids and oxidants such as chlorine may accelerate degradation of nearby materials. Therefore, it is advantageous to identify PVC in collections. However, identifying a specific type of plastic is not easy. In the past, identification has relied on visual clues, maker’s marks, and burn tests. More concrete analysis is possible with the use of analytical equipment such as pyrolysis gas chromatography – mass spectrometry (Py-GCMS), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. However, access to such equipment and expertise to use it is typically the domain of larger, well-funded museums. Since the majority of museums are small, understaffed, and underfunded institutions, access to scientific analysis is limited. Having an easy-to-use, inexpensive method of detecting chlorine that may be emitted from PVC would greatly benefit many museums because knowing if a plastic is emitting an oxidant could influence storage, display, and deaccessioning decisions. In spring 2018, Mary Coughlin, Assistant Professor in Museum Studies at The George Washington University, G. Asher Newsome, PhD, Physical Scientist at the Smithsonian Museum Conservation Institute, Gwénaëlle Kavich, Conservation Scientist at the Smithsonian Museum Conservation Institute, and Qiuhui Wang, graduate student in Environmental and Green Chemistry from The George Washington University, tested commercially available Ozone Test Strips that are marketed as detectors for the presence of ozone in the environment but, according to the instructions, can get a false positive for chlorine. This project aimed to determine if Ozone Test Strips could be repurposed to detect chlorine that may be emitted from PVC. The study found that The Ozone Test strips will react to chlorine, as demonstrated by testing with hydrochloric acid solution as well as testing with a chlorine gas wafer and a hydrochloric acid permeation tube in a dynacalibrator pollutant generator. The Ozone Strips reacted to severely degrading PVC samples and to a few PVC items that still looked to be in good condition (all identified with FTIR and XRF). However because the Ozone Test Strips reacted to one non-PVC item (acrylic identified with FTIR), questions are raised about how useful the Ozone Strips are for identifying PVC and whether it is enough to use them as an indicator for oxidants coming from plastics in general. More work is planned for the fall and winter in setting up low-tech testing of plastic samples in sealed glass beakers and monitoring with the Ozone Strips. The goal is to present results and to gather ideas for what the strips are reacting to in order to better understand the chemistry involved in these interactions and if these strips can be utilized in museum collections.

2019 | Uncasville | Volume 26