Lecture Summary by
Austin Plann Curley
Conservation Intern at the Folger Shakespeare Library

Evaluating Storage Materials: Alternatives to the Oddy Test

Eric Breiting spoke October 2 on his ongoing work at Library of Congress to develop an alternative to the traditional Oddy Test better suited to paper-based collections. This WCG-sponsored event was held at the Holocaust Memorial Museum and drew a full audience of students and professionals from conservation and other cultural heritage professions.

The traditional Oddy Test uses coupons of copper, lead, and silver as sensors to evaluate suitability of materials for use in contact or proximity to collection objects such as mounts for display or storage enclosures. Under controlled conditions, a coupon that tarnishes in proximity to the test material suggests off gassing from the test material. Based on a visual analysis of the tarnished coupons, materials are placed in one of three categories: unsuitable, suitable for temporary contact, and suitable for permanent contact.

Breiting, a senior scientist at Library of Congress, began his research by asking what types of gasses are detected by the traditional Oddy Test. He performed the Oddy Test on a variety of common housing materials – binder’s board, foams, adhesives – and analyzed the corrosion products using X-ray Diffraction (XRD). The products, in all cases, suggested mechanisms involving acids – presumably volatilized from test materials – and water, which is present in monolayers at the metal surface.

Breiting posed the question: Are metal coupons good surrogates for paper based collections? The LOC test developed by Breiting and his colleagues used 100% cellulose Whatman filter paper as a sensor, enclosed with two grams of test material at controlled relative humidity and temperature. The paper sensor is then extracted into water and the extract is analyzed using Ion Chromatography-Mass Spectroscopy (IC-MS). Degradation to the cellulose is gauged by comparing peak heights at key points on the y-axis. Similar to the Oddy Test, materials can be characterized as unsuitable, suitable for temporary contact, or suitable for permanent contact. The Oddy Test and Breiting’s alternative do not always give confirming results, though the variations cannot be generalized.

In the end Breiting did not dismiss the Oddy Test completely, but rather characterized it as sufficient for catching “the worst actors” in terms of materials. Furthermore, he felt it was more appropriate for metal-based collections than for paper-based collections. Whatman filter paper, on the other hand, was proven to be an effective sensor for measuring damage to cellulose, the downside being cost and limited access to IC-MS. For conservation labs without access to IC-MS, a UV-vis spectrometer – equipment with a considerably lower price tag – is an alternative option for analysis.

Panel Summary by
Allison Rabent and Adam Wiener
Conservation Interns at The United States Holocaust Memorial Museum

Panel Discussion
Participants:
Eric Breitung, Senior Conservation Scientist, Library of Congress
Christopher Maines, Senior Conservation Scientist, National Gallery of Art
Robyn Hodgkins, Conservation Science Fellow at the National Gallery of Art
Elena Torok, Project Conservator in Objects Conservation, Yale University Art Gallery
Jennifer Bosworth, Exhibits Conservator, Freer and Sackler Galleries of Art

Question: If the Oddy test primary detects acids, is there a simple way to test for acids with a pH meter or strips?
Panelists identified several obstacles to testing materials in this way, such as the difficulty in testing a solid material, and the inability to account for degradation over time. Christopher Maines pointed out that SPME can be used as an alternative to the Oddy with successful results, but requires highly specialized equipment.  Elena Torok also discussed her work surveying 43 institutions on their methods of Oddy testing. 31 do their own testing, and among them were 19 different variations on the two published methods of testing (Bamberger, 1999 and Robinett and Thickett, 2003). Several institutions claimed to be using one of these two procedures, but the steps they described differed from the published methods.

Question: Is there any control for Oddy testing?
Panelists explained the different procedures at their institutions, using positive and negative controls. Ultimately, the best way to get consistent results within an institution is to have the same person run the test each time.

Question [for Robyn Hodgkins]: Did you make any modifications to the test when working with extra sensitive materials, such as daguerreotypes?
Hodgkins explained that she made her own silver nanofilms which were much more sensitive and gave visually discernible results.
(Robyn’s paper that includes the details of the silver films with testing results can be downloaded for free here: http://www.morana-rtd.com/e-preservationscience/2013/Hodgkins-06-02-2013.pdf)

Question: For institutions that have Ocean Optics equipment to do UV-Vis testing, but could not afford more specialized (IC) equipment, could UV-Vis work in tandem with the Oddy test?
Breitung felt that the Oddy test did not have a significant relationship to the UV-Vis results.

Question: Have there been any instances when a material passed the Oddy test, but then caused problems later down the line?
Maines had encountered this issue in the past, but not in the last fifteen years. It is always possible for a material to be harmful even if an object shows no damage, especially if it is only exposed for a short period of time.