Master – thesis abstracts 2017
Franziska Jakobi. Wheat starch paste variations: adherence in reference to modification and mixture. The strength of several adhesives preparations was tested at 11 different aqueous dilutions (1:2–1:40): wheat starch paste, mechanically stressed wheat starch paste, pure amylopectin paste, hydroxyethylcellulose (Tylose) and mixtures of wheat starch paste and hydroxyethylcellulose. The adhesives iodine-potassium iodide stained, photographed at 500x; they were applied to paper and air-dried, employed in lining test papers and peel-tested. Except for the amylopectin which failed, the other adhesives provided sufficient strength for adhesions.
Benjamin Kirschner. LED as a source for artificial light bleaching. Testing in comparison with other artificial light bleaching methods. Light emitting diodes (LED) are the most energy efficient and brightest light sources currently available. The present investigation tries to evaluate their properties for the application in artificial light bleaching treatments by comparing them with the well- established HID lamps. Although these lamps are suitable for light bleaching their application is limited to a quite far distance from the object due to their heat emission. The light intensity on the object is significantly reduced. LED show various properties enabling them to be positioned in a closer distance. For the investigation two industrial LED modules with 4000 K and 6500 K light temperature are chosen and installed in a test device. Samples of two naturally aged rag papers are bleached in immersion bath for 2 h and 4 h in a distance of 10 cm and 20 cm. The results are compared with samples bleached by HID in a distance of 60 cm and 120 cm for the same time. The colour of all paper samples is determined before and after treatments with a spectrophotometer in the L*a*b colour space. The colour change is calculated based on CIE76 and CIE2000. The light intensity measured by a photometer lies between 50.000 lx and 300.000 lx. No significant amount of UV radiation can be identified. The most intense bleaching by LED takes place at the highest luminous intensity after 2 h of treatment. The speed of bleaching by the LED is notably faster than the one observed at the HID lamps. To verify the test results a mid 1940ies original etching is treated with 200.000 lx for 4 h. Results show that the heavy discolouration can be removed almost completely. In conclusion, the presented results show that the tested LED are able to improve the efficiency of light bleaching treatments and should be considered for further research. Publication: submitted to Restaurator Dec. 2018.