Page - 143 - in The Vienna Genesis - Material analysis and conservation of a Late Antique illuminated manuscript on purple parchment

Rabitsch, Malissa, Hradil, Erlach, Uhlir, Griesser, Hofmann 143 XRD analysis was by chipping, the calcite can be assigned most likely to the parchment. The main corrosion product of the ink is silver chloride consistent also with the XRF an- alysis of the chemical elements. No crystalline copper compounds were detected on the original Vienna Genesis samples by XRD. A selection of reference silver inks, unaged and artificially aged, were analysed with the µ-X-ray diffraction phase analysis. The analysis of samples from the reference inks ST1 and ST2 are illustrated in figure 24 and 25, respectively. Besides the pure silver phase (ST1, ST2) and the hair copper phase used within the ink mixture for ST1, we found a con- siderable amount of calcite and/or dolomite phase, which also explains the high calcium content within the XRF analysis. It can be assigned most likely to the sample preparation procedures or the treatment of the parchment, for example grinding of silver in a mortar or preparing the animal’s skin with lime. We can find a tiny amount of a corrosion product for both ink samples, i. e. silver chloride (AgCl; chlorargyrite) even in the unaged and un- treated sample. The aging procedures and the different treatments yielded additional cor- rosion products as silver oxide (Ag2O) and silver chlorate (AgClO3). Their relative amounts vary considerably in the different samples. Based on presence of chlorargyrite as the main corrosion product and the assumption of a contact with seawater for the parchment, in- situ ageing experiments within a reaction chamber using seawater aerosols and temper- atures up to 300 °C were performed during the XRD measurements to follow the phase development during these treatments. The details of the analysis of the aged reference inks and the in-situ investigations are discussed in a further publication48. Analysis of the silver ink with SEM/EDX Energy dispersive X-ray analysis in the scanning electron microscope (SEM/EDX)49 was employed for additional characterisation of the silver ink. Micro-samples of silver ink from Vienna Genesis and the reference ink ST1 from the alteration study were investigated by SEM/EDX. The samples are listed in Table 2 (chronological order as provided for analysis). Samples T2, T5, T6 and T11 were taken by slightly scratching the surface of inked areas on the Vienna Genesis with a scalpel. Sample T17 was taken as one cross-section from an inked area on folio 22 with a loss. The samples contain ink and parchment. Sample Pe1 was taken from parchment without ink on the inner edge of folio 22. For comparison, samples were taken from reference ink ST1, unaged and aged. ST1 is a silver ink which contains sodium chloride and copper(1)oxide, see chapter on the alteration study. 48 Hradil et al., to be published. 49 SEM/EDX analysis was carried out by Rudolf Erlach. Open-Access-Publikation im Sinne der CC-Lizenz BY 4.0