Nedfästning av oljemåleri på puts. En fallstudie från salongen på Mostorps slott i Halland

Abstract

This thesis, designed as a case study, is about complications concerning conservation of a decorative oil paint on lime plaster from the drawing-room in Mostorp castle sited in the county of Halland in south-west of Sweden. The building was built 1878-80 with an exterior of granite. The interior walls were made of clay bricks, lime mortar and lime plaster. The oil paint is applied to a layer of putty. The combination of different materials, which are organic and inorganic, affects the movement caused by internal and external stress. In the end this might result in cracks in the weakest layer, that is, in the layer of putty.

The aim of the thesis was to investigate reasons for the difficulty with the fixation of the oil paint with a layer of putty underneath. Studies were carried out on the different materials of the wall and also on the effects on material due to environmental and inherent reasons. Through discussion with master painters knowledge were gained about the way of work with the layers between the oil paint and lime plaster.

Test samples were taken from the wall to find out if the reason of the difficulty with the fixation could bee seen in microscope. Two tests were casted into cross-sections. One test was analysed after a Biuret-test to find out if the sample contained protein. No reaction was detected. The next test was with Rhodamin-B to find out if the material contained dried oil. In this case a positive result was given. The cross-section showed in which of the wall layers the split was located, namely the layer of putty.

Plextol D528 and Acronal 300D are dispersions of synthetic adhesive and were used in the conservation of material in this case study. A study of physical facts about these two adhesives was carried out. Acronal and Plextol have similar characteristics and it is therefore difficult to motivate why Plextol gave reduced fixation of the oil paint to the putty layer. Hypothetically, the reason could be that Acronal has less surface tension and a lower viscosity and achives therefore a higher degree of absorption. A heat-spatula was used when the adhesive did not fix to the layer underneath. Still there were parts with loose oil paint; however, Acronal was used to overcome this problem.