Chemistry meets art: How are chemicals used in art restoration?

Students from four schools from across Europe learned about the exciting topic of how chemicals are used in art restoration in the French-speaking Xperimania online chat on 5 February 2009. The chat expert Mrs Myriam Serck-Dewaide, Director General of the Belgian Royal Institute for Cultural Heritage, explained to the students how chemistry helps to preserve the world’s artistic and cultural heritage.

Students from Belgium, Slovenia and Romania had prepared several interesting – and not so easy-to-answer – questions for the chat expert. The Institut Saint-Sépulcre, in Liège, Belgium, opened the chat. To set the scene, Myriam Serck-Dewaide explained that petrochemicals, such as solvents, are used extensively in art restoration, to remove touch-up areas or deteriorated varnish on painting and polychrome sculptures.

One of the Belgian students wanted to know since when petrochemistry has been used in art restoration. Myriam Serck-Dewaide replied that it started in the early 60s with synthethic products used in cleaning, consolidation and pasting processes.

The pupils from the Technical College Dimitrie Ghika, in Comenesti, Romania, asked how the physical and chemical characteristics of materials in a work of art are identified. The chat expert described the process:

“The first step in studying the materials of a work of art is to examine them under a microscope. If necessary a microscopic sample of the material can be taken and fixed on a plexiglass plate to examine it under a scanning microscope. This will help to identify the pigments that constitute the colours of an ancient painting, for example.”

Myriam Serck-Dewaide also said that works of art can survive a large amount of restoration without losing their originality:

“Works of art have been restored and preserved since Antiquity. Proper treatment doesn’t damage the work. Nevertheless, some amateurs have spoiled some works.”

It is therefore important that any mixture be previously and carefully tested.

The students from Gimnazija Poljane in Ljubljana, Slovenia, were concerned about the durability of the works of art after using polymers, and the impact of heat, ultraviolet rays and humidity on them.
 
“Normally, the resins chosen must be stable for a minimum of 100 years,” explained the chat expert.

“The stability of resins is determined according to laboratory rules and aging tests. Nevertheless, some products don’t withstand time and must be removed. Heat, ultraviolet rays and humidity damage the original materials and the chemicals added to works of art. This is why it is important to keep works of art in a stable and controlled environment.”

The students from the Colegiul Technique "Dorin Pavel", in Alba Iulia, Romania asked for more specific information, such as whether a wooden icon painting can be cleaned with ammonia. Myriam Serck-Dewaide explained that one or two drops of ammonia should be mixed with water to clean the varnish, but ammonia should not be used directly on the painting.

The students of Institut St Sépulchre in Liege were also interested in replacing petrochemicals with natural products in art restoration. The chat expert pointed out that natural and synthetic products are very often used together to create mixtures of substances that are suitable for particular works.

After the one hour chat, the students had learned a lot about how two seemingly very distant fields such as art and chemistry are coming closer to each other, and what to do - or not to do - when you want to preserve a work of art for future generations.

Download the chat transcript here (pdf, in French).

Background article

Gimnazija Poljane, Slovenia 
Teacher: Breda Policar
Chat expert Myriam Serck-Dewaide discusses the answers with Ann Whent, Appe, and Pierre de Kettenis, Cefic/ Appe.
Chat expert Myriam Serck-Dewaide and Pierre de Kettenis, Cefic/ Appe. Ann Whent, Appe, helps with the typing.