Decontamination and “deconsolidation” of historical wood preservatives and wood consolidants in cultural heritage

In the past, wood artifacts were treated with a variety of wood preservatives formulated on the basis of inorganic and organic biocides. Most of these biocides have a high human toxic potential and pollute the environment. Some of them even cause damage to the objects they were meant to preserve. This poses a considerable challenge to the handling, exhibition, storage and restoration of such wooden works of art. In addition, biocide-containing structural wood members in historic buildings pollute the indoor-air, and represent a permanent health risk. Wood artifacts previously damaged by organisms and subsequently preserved and consolidated with mixtures of vegetable oils and natural resins now show characteristics of renewed deterioration. An important condition for the re-treatment of such objects is the exact detection of the substances originally utilized for their conservation. Non-destructive and in situ-measurements have priority among the listed analytical methods. The various decontamination procedures currently used are classified in regard to their mode of operation. Preferred methods include mechanical cleaning, thermo desorption, washing with water and detoxicants, and leaching as well as extraction with liquid or supercritical carbon dioxide. The masking with various sealers to prevent biocide evaporation into the indoor-air is limited to application to structural wood members. Leaching of degraded natural consolidants in wood artifacts is currently undertaken in a testing plant.