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Analysis of historical impregnations with carbolineum as the basis for conservational decontamination and model-based testing of new decontamination technologies

The aim of the project is to find a compatible solution for the reduction of hazardous oily residues on ecclesiastical wooden objects that were treated in the past with carbolineum.

Carbolineum is made of a mixture of different tar oils, which are derived from the distillation of coal tar. It works both as an insecticide and a fungicide and can therefore help to prevent wood from rotting even when exposed to extreme weather conditions. Today, carbolineum is classified as carcinogenic because it contains polycyclic aromatic hydrocarbons, and its use is prohibited.

The tar oils in question belong to the group of non-drying oils, so it must be assumed that they are continuing to cause damage even today. The porosity of wood and the mobility of carbolineum results in discoloration and the deterioration of the original polychromy. Microscopic analyses frequently reveal a layer of carbolineum with a viscous or hard, elastic consistency between the original and later coats of paint. At times, the carbolineum may be sweated out, forming small droplets on the surface of the object. No scientific studies on how to conserve and treat such objects have been published to date.

The proposed project aims to research possibilities for reducing the level of carbolineum contamination in selected historical wooden objects.

The success of prior attempts at restoration has only been short-lived despite the removal of the base coat and other layers of paint impregnated with carbolineum as well as the additional application of an insulating sealant to the underlying substratum. The project thus aims to advance knowledge and provide valuable insights into the ageing process of historical applications of carbolineum that have migrated for more than a century, and to open up possibilities for reducing and breaking down the constituents of carbolineum.

Project sponsor: Deutsche Bundesstiftung Umwelt (DBU)
Project coordinator: Rathgen-Forschungslabor
Project partners: Hochschule für Bildende Künste Dresden, Bundesanstalt für Materialforschung und -prüfung Berlin, Landesamt für Denkmalpflege Schleswig-Holstein, Nordelbisches Kirchenamt, Markus Freitag (consulting conservator)
Funding: supported by the DBU
Duration: 2013 to 2014