Seite - 17 - in The Vienna Genesis - Material analysis and conservation of a Late Antique illuminated manuscript on purple parchment

Christa Hofmann, Sophie Rabitsch 17 could not be delivered. To enforce the seizure the Italians took three of the most valuable objects of the library, one of them the Vienna Genesis, as security. After tedious nego- tiations and a special contract with Italy, the three manuscripts were returned in March 1921. Prior to their transport to Italy the surface of the glass plates that housed the folios of the Vienna Genesis had been glued with paper adhesive tapes, which served as protec- tion against breaking of the glass. Following their return, the removal of the tape was not completely possible, as the glue had damaged the glass surface. The glue was analysed by the “Landwirtschaftliche-chemische Bundesversuchsanstalt” (agricultural-chemical federal research institute). Director Otto Dafert summarised the findings in a report to the Na- tional Library24. The glue contained hydrofluoric acid, which damaged and roughened the surface of the glass. During analysis of the glue, a coating covering the inner surface of the glass plates was discovered. It was described as oily droplets with a tendency to crystalliz- ation. Investigations revealed that the coating consisted of sodium acetate, but free acetic acid was not detected. Dafert assumed in his report that the glue which was used to hold the glass plates together in the late 19th century contained acetic acid, which later led to the observed coating. A fading of the purple dye was observed since Chmelarz’s encapsulation between glass plates. In his report, Dafert states that the glue containing acetic acid could have caused this phenomenon. The library’s director general Donabaum wrote to the federal minister for interior and education to ask for the financial means to buy new glass plates. He refers to the bad condition of the folios and to the frequent use: “… a different storage than between glass plates is not possible considering the bad condition of the folios and the frequent use of the manuscript.”25 The Italian government was asked to pay for 52 new glass plates (2.5 mm thick, 46.5 x 34.5 cm, all four edges polished). The director general’s argument was that foreign visitors wanted to the see the manuscript almost daily. The request was granted and the folios were rehoused between new glass plates. A second facsimile edition was produced in 1931 with a commentary volume by Hans Gerstinger. Kunstanstalt Max Jaffé reproduced the folios as colour collotypes. In the com- mentary, Gerstinger described different shades of purple on the folios and attributed them to chemical changes and fading of the colorants26. These observations led him to the con- clusion that the colorant was “artificial purple” rather than shellfish purple, a reasonable assumption as shellfish purple is known to be a rather lightfast natural dye, see chapter on purple parchment. A sample was taken to identify the colorant but without result27. Ger- 24 Dafert, Austrian National Library Archive, record 775/21, 1921. 25 Donabaum, Austrian National Library Archive, record 775/21, 1921. 26 Gerstinger, 1931, p. 29. 27 Gerstinger, 1931, p. 187. Open-Access-Publikation im Sinne der CC-Lizenz BY 4.0