Page - 270 - in The Vienna Genesis - Material analysis and conservation of a Late Antique illuminated manuscript on purple parchment

270 Conservation of the Vienna Genesis and the new storage system KR4C coated with isinglass-Klucel G 5 %, 1:1 v/v und Klucel G 5 % (in water) gave the best results. Both show sufficient adhesion on the smooth and thin parchment. The coating with the isinglass-Klucel-mixture adheres better. Both remoistenable tissues have a closed surface after drying, while on the tissues coated with gelatine and isinglass alone, the surface is fibrous. Klucel is a hydroxypropyl cellulose ether that is soluble in water and ethanol38. Klucel G is of medium viscosity and adhesion strength and has been used in conservation for over 25 years. It is the second best film former among cellulose ethers39. The studies by Feller rated the adhesive as less stable than methylcellulose given the degree of yellowing ob- served upon ageing of the dry undissolved powder40, but the long-term stability is reason- able at low concentrations of dissolved Klucel G41. Ageing tests of remoistenable tissues coated with Klucel G showed good colour stability after ageing42. Isinglass-glue is made from the swim bladder of the sturgeon. It shows high adhesive strength and low viscosity43 and is a traditional conservation material for the consoli- dation of paint layers; the Paintings Conservation Department of the Kunsthistorisches Museum Vienna has long-term experience in its use. Isinglass is an elastic adhesive that is low in tension44 with a similar refractive index to parchment45, is soluble in water and according to Pataki, no more than 50 % v/v of ethanol should be used for reactivation of a coated tissue46. Sometimes a tendency for yellowing and embrittlement is described, but when the adhesive is of good quality, this should not occur47. As it is a natural prod- uct, the quality can vary. For this project isinglass was obtained from Störleimmanufak- tur48, a company which uses swim bladders of consistent quality from sturgeons raised in aqua-cultures in Germany. The adhesives which worked best on Cod. Ser. n. 2804 were tested on the inner mar- gin of folio 7, page 13, using KR4C and different methods of activation (Table 6). The small bridges of tissue were mechanically removed afterwards. Klucel G as well as the mix- ture of Klucel with isinglass seemed to be suitable for the mending of inked areas in the 38 Reuber, 2010, p. 30. 39 Pataki, 2006, p. 38. 40 Feller and Wilt, 1990, p. 93. 41 Pataki-Hundt, 2012, p. 157. 42 Hofmann et al., 2015, pp. 171–172. 43 Ritter and Masson, 2005, p. 27. 44 Fuchs et al., 2001, pp. 90–91. 45 Fuchs et al., 2001, p. 18. 46 Pataki, 2009, p. 56. 47 Wikarski, 2012, p. 81. 48 http://www.stoerleim-manufaktur.de/ (accessed 19 December 2018). Open-Access-Publikation im Sinne der CC-Lizenz BY 4.0