Seite - 115 - in The Vienna Genesis - Material analysis and conservation of a Late Antique illuminated manuscript on purple parchment
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Maurizio Aceto, Maria João Melo, Elisa Calà, Paula Nabais, Rita Araújo 115
the transformate F(R) = (1-R)2/2R. The Kubelka-Munk function allows appreciating dif-
ferences due to the concentration of the absorbing species, orchil in this case. It can be
seen that, despite the differences in tone of the respective folios, all FORS spectra show
the same features, that is two maxima at approx. 542 and 586 nm, typical to orchil. The
differences in the spectra can be explained in terms of residual concentration of the dye on
parchment.
After considering the differences potentially introduced by the action of artisans, the ef-
fects of the environment must be considered. Orchil is not a lightfast but rather a fugitive
dye, i. e. it can fade due to the action of light. In addition, its hue is strongly dependent
on pH16 and redox conditions. Exposure to light, contact with chemical substances (from
cleaning products to any kind of chemically active substrate, such as wine, vinegar, etc.)
and proliferation of microorganisms are all possible causes for the occurrence of darker and
paler areas. A further element of variation could be the preparation of orchil from lichens.
As mentioned earlier, this dye was extracted from several species by soaking lichen scraps
16 Consider that a polymeric form of orchil, the so-called litmus, is nowadays exploited in litmus
paper.
Fig. 10: FORS spectra in F(R) coordinates of light, medium and dark purple folios of the Vienna Genesis.
Open-Access-Publikation im Sinne der CC-Lizenz BY 4.0
The Vienna Genesis
Material analysis and conservation of a Late Antique illuminated manuscript on purple parchment
- Titel
- The Vienna Genesis
- Untertitel
- Material analysis and conservation of a Late Antique illuminated manuscript on purple parchment
- Herausgeber
- Christa Hofmann
- Verlag
- Böhlau Verlag
- Ort
- Wien
- Datum
- 2020
- Sprache
- englisch
- Lizenz
- CC BY 4.0
- ISBN
- 978-3-205-21058-0
- Abmessungen
- 17.3 x 24.5 cm
- Seiten
- 348