Evaluation of the effects of four consolidants on matte paint and their ageing

Sammanfattning: This research starts with the analysis of the funeral coat of arms of Pehr Stålhammar, dated 1701, as a case material of matte paint in need of consolidation. This study aims to assess the effect of four consolidants on matte paint and their ageing properties. The materials identified in the paint layer include smalt blue and lamp black as pigments and egg white as binder, and chalk and rabbit skin glue in the ground layer by microscopy and analysis with Fourier-transform infrared spectroscopy. Mock-ups were created as replicas of the blue and black paint layers with the information obtained by the analysis and literature on matte paint techniques, and artificially aged in a first cycle with indoor climate conditions. The mock-ups were consolidated with Lascaux’s Medium for Consolidation 100% and 25%, Aquazol 200 5%, sturgeon glue 3% and JunFunori 1% in water solutions, then exposed to a second cycle of artificial ageing in order to assess the reaction changes between the added consolidants and the paint. The physical properties studied were the changes in gloss with a gloss-meter, changes in color by the use of spectrophotometers, morphology and cohesion bonds by Scanning Electron Microscope and cohesion power by test tape. The chemical properties were studied by the use of Fourier-transform infrared spectroscopy. In the results, oxidation of the sturgeon glue after artificial ageing could be noticed. The magnified images of the aged JunFunori show an efficient performance in the bonds. The largest changes in gloss occur in the lamp black paint, and the most changing consolidant over time is the sturgeon glue which increases in gloss. The color measurements showed that lamp black is more affected by the consolidation than smalt blue and that the most darkening effect is caused by Aquazol 200, but showed minor differences after artificial ageing. In the cohesion test, all of the tested mixtures appear to consolidate efficiently the friable paint layer.