Restaurator, Vol. 33, p. 249–273 © De Gruyter Saur 2012 An Evaluation of Historical Bleaching with Chlorine Dioxide Gas, Sodium Hypochlorite, and Chloramine-T at the Fogg Art Museum by Theresa Smith Abstract: In the mid-twentieth century, drawings by Jean-Auguste-Dominique Ingres at the Fogg Art Museum were treated with chemical bleaches such as chlorine dioxide gas, sodium hypochlorite, and chloramine-T. Fifty years later, the darkened condition of the drawings was attributed to bleach- ing with chlorine dioxide gas. This paper discusses the three methods developed by Rutherford John Gettens to generate chlorine dioxide gas from sodium chlorite, formaldehyde and formic acid, examines the use of these bleaching methods to treat Ingres drawings at the Fogg, and discusses the sodium hypochlorite and chloramine-T bleaching methods also in use at the time. The treatments of two Ingres drawings are compared and evaluated in light of later bleaching studies and the cur- rent condition of each drawing. All of these historical bleaching methods, as practiced on the works studied, contributed to the darkening and colour/brightness reversion of drawings. Zusammenfassung/résumé at end of article received: 01.07.2011 revised: 16.05.2012 249 DOI: 10.1515/res-2012-0012 1. Brief history of conservation at the Fogg Art Museum The Fogg Art Museum at Harvard University (now the Harvard Art Museums) was instrumental in establishing scientific conservation practices in the Unites States. Mu- seum director Edward Waldo Forbes and his assistant Paul J. Sachs were committed not only to collecting art, but to understanding the techniques and materials used in the creation of artworks as well as the factors affecting their deterioration. Under their leadership, the Fogg Museum was envisioned to be a “laboratory for art” and the De- partment of Technical Studies was created to support research in these areas (Bewer 2010). Forbes hired two staff members for the new department: art historian and conservator George Stout and chemist Rutherford John Gettens. In the early 1930s, Minna Horwitz and Evelyn Ehrlich began volunteering in the Department of Techni- cal Studies and assisted Gettens and Stout on a variety of research projects, such as studying the moisture permeability of different surface coatings for paintings, prevent- ing mould growth in adhesives, transferring Asian wall paintings to new supports, and studying the oxidative bleaching of cellulose (Fig. 1). Under Stout and Gettens’s supervision, Ehrlich and Horwitz were primarily responsible for the conservation of