Seite - 163 - in The Vienna Genesis - Material analysis and conservation of a Late Antique illuminated manuscript on purple parchment

Sophie Rabitsch, Antonia Malissa, Katharina Uhlir, Martina Griesser, Christa Hofmann 163 The third process to obtain fine silver powder is by the formation of silver amalgam14. Silver leaves or chips are ground with mercury in a porcelain bowl while being slightly heated. When the temperature is raised, mercury evaporates while a fine silver powder remains. In the course of the sample preparation, silver chips were ground with mercury in a porcelain mortar while being heated with a Bunsen burner15(Fig. 6). After one hour of grinding the silver powder seemed to be fine enough and the silver amalgam was further heated for 30 minutes. After the refinement of the silver, the required amount of silver powder was transferred into a small glass bottle (Fig. 7) and mixed with the additives and a liquid binder, im- mediately before the application of the inks on the parchment samples. Different types of parchment were used, which is explained below. Parchment was dyed purple with orchil (obtained from Roccella tinctoria) and cut to a sample size of between 2.5 x 2.5 cm and 3 x 3 cm in sub study 1 and 5 x 4 cm in sub study 216. For writing, hand carved bamboo pens17, replicating the Late Antique calamus, were used, see chapter on the silver ink (Fig. 8). In order to avoid contaminations of the inks by each other, individual pens were used for each ink. Greek letters were written on the purple parchment samples. During the final step of the sample preparation, the silver inks were burnished with an agate polishing stone under low pressure18. In the course of the experimental preparation of the reference inks some of the recipes taken from Trost’s book had to be modified in order to improve their usability. The in- gredients and the qualities of the 14 reference inks are described below. Sub study 1: ST1–ST9 Reference ink ST1 For the production of ST1, recipe CL N 3–13 (variation V, model 40)19 by Trost was used. The recipe originates from the Lucca manuscript and therefore can be dated to the 7th or 8th century. The reference ink is categorised as a silver ink with metallic and non-metallic 14 Schreiner and Oltrogge, 2011, p. 137. 15 This part of the experiments was executed under the fume hood in the laboratory, considering the required safety measures. 16 The samples were larger in sub study 2, as more parchment was available at that time. 17 The technique was kindly demonstrated by Cahit Karadana. 18 In the literature, hematite, sardonyx, wolf or dog teeth are mentioned. One could also put a piece of textile like silk for protection in between. Schreiner and Oltrogge, 2011, p. 111. 19 Trost, 1991, p. 117. Open-Access-Publikation im Sinne der CC-Lizenz BY 4.0