Seite - 92 - in The Vienna Genesis - Material analysis and conservation of a Late Antique illuminated manuscript on purple parchment

92 Purple dyeing of parchment cause the suspended particles have sunk to the bottom of the container (Fig. 17). The vat has to be kept warm and in a double boiler during the whole process. It is im- portant to constantly protect the vat from larger amounts of oxygen (for example through stirring) and sunlight. If wool or other textiles are dyed, the vat’s temper- ature of 45–48 °C is perfect, but for dyeing parchment, the vat should be at maximum 25 °C. The vats for these experiments con- sisted of snail glands with some adher- ent flesh, rainwater and putrid urine. No other chemicals, such as sodium hydrox- ide or sodium dithionite, were used. With the use of such chemicals, the reduction would be achieved in one hour, whereas the old-style vat takes about a week to produce quality results. Two vats were pre- pared, one made of frozen glands and one made of fresh glands. Each vat contained about 1.5–2 litres of liquid. Application Different types of parchment were dyed: Late Antique style lamb parchment by Jiří Vnouček as well as lamb, adult sheep, hare, calf and deer of unknown origin. To make handling of the pieces easier, cotton strings were attached, so that they could be moved easily inside the vat. Before immersing the parchment into the vat, it was soaked in a mild mixture of vinegar and water to ease the absorption of the dye. To obtain even results, it is important to make sure that the pieces of parchment are not folded or sticking together when immersed in the vat. The parchments were left for about one hour inside the vat, which has to be protected from oxygen and light in this stage. After removing the parch- ments from the vat, they were soaked in vinegar water again. The oxidation process can be observed within a few minutes (Fig. 18). The samples of parchment were dried stretched, using pins on a polystyrene board (Fig. 19). The colours turned out intense and even and ranged from an almost pinkish Fig. 17: Vat ready to dye in a double boiler. Open-Access-Publikation im Sinne der CC-Lizenz BY 4.0