Preventive Conservation Dilemmas for Artworks Exhibiting Soft and Dripping Paint – The Impact of Changes in Relative Humidity on Soft oil Paint in Paintings by Karel Appel and Asger Jorn

In response to the recent trend of implementing less stringent climate control practices for museum exhibition and storage areas, issues related to the conservation of soft and dripping paints need to be addressed. Soft and dripping paint has been documented in paintings created by more than 30 Western artists between 1917 and 2008, with the majority executed in the twentieth century. For conservators, it is important to recognize the condition issues as they indicate several kinds of sensitivities to high relative humidity, transportation, vibration, touch, and solvents. Risks connected to soft oil paint are an understudied area. Through novel nanoindentation testing of micro samples, performed in a climatic chamber, a correlation has been established between increased relative humidity and increasing softening for soft bone black paints identified in oil paintings by Asger Jorn (1914–1973) and Karel Appel (1921–2006). These paints were also tested for dynamic vapor sorption (DVS) to determine their moisture sorption isotherms. This paper will discuss what these new nanoindentation findings can mean for preventive conservation of paintings composed of soft and dripping paints.