Colourful wall hangings may be toxic
Traditional Swedish bonad paintings could contain toxic substances like arsenic, a new research has revealed.
In the research, painting conservator and conservation scientist Ingalill Nystrom from the University of Gothenburg's Department of Conservation analysed the paint and techniques used in the traditional painted wall hangings from southern Sweden.
Bonad paintings are painted wall hangings that tell a story, often with a biblical theme. However, there has, to date, been little information available about the paint and materials used.
"It's important to know about the materials used in these wall-hangings so that we can preserve them," Nystrom said.
"We need to know whether they run the risk of being bleached or broken down by different kinds of exposure, treatment or conservation method.
"It's also important for the people who handle them to know whether any of the substances in them could be harmful or toxic," she said.
Several toxic pigments have been found in the wall hangings studied, including orpiment and emerald green, which contain arsenic.
Orpiment was very common in yellow pigment in painted wall hangings throughout the 18th century and well into the 19th century too. Emerald green appears in some 19th century wall hangings.
"So it's important to be careful when handling them. Several of the pigments and dyes are also sensitive to light, and the binding agent in the hangings is sensitive to damp and moisture," she said.
Nystrom has examined more than 70 bonad paintings originating from southern Sweden between 1700 and 1870, and also 700 paint samples.