DELAMINATING PAINT IN AN 18TH CENTURY CANVAS WALL PAINTING A Case Study at the von Echstedt Manor

Abstract

This study investigates the cause and progression of the ongoing deterioration in a canvas wall painting from the 1760s in the Green Chamber at the von Echstedt manor. In an area approximately 170 x 170 cm on the south wall, the paint is severely delaminating despite several attempt to consolidate it. In the same area the paint is also significantly darkened. The painting is examined in situ and documented in UV-light, raking light and with a usb-microscope. Samples are collected for microscopy and material analysis. Cross sections are made from the paint samples. Two cross sections are analysed with SEM-EDS for pigment identification. The pigment used for the ground layer is identified as chalk. The prevailing pigments in the paint layers are identified as lead white and malachite, other pigments present seem to be carbon black and verdigris. Signs of lead soap formation are seen in the SEM-EDS analysis together with the SEM-BSE images. Samples of paints and varnish are analysed with FTIR-ATR to determine their molecular composition. The binder used in the ground is probably an animal glue, and in the paint layers the binder is identified as an oil. A varnish applied in the 1950s is a mastic varnish. The unregulated indoor climate of the Green Chamber is monitored over six months (Oct – Apr) and show an RH up to 88%, with daily fluctuations around 10% and a temperature down to -8 °C. Archival records are searched for information on previous treatments. A photograph from wallpaper removal during a restoration in the 1950s show extensive paint losses in the area of the painting that today is suffering from delamination. It is concluded that the paint losses from the 1950s wallpaper removal have created an area of the painting that is more sensitive to both climatically induced deterioration and lead soap formation.