Re-conservation of Wood from the Seventeenth-Century Swedish Warship the Vasa with Alkoxysilanes: A Re-treatment Study Applying Thermosetting Elastomers

The purpose of this study was to explore the feasibility of re-treating artifacts previously conserved by PEG impregnation with alkoxysilanes. The study tried to evaluate pros and cons of re-conserving artifacts with this type of silanes. A series of experiments were conducted focusing on small, wood samples from the Vasa Museum Collection, to test different re-conservation methods. Three different procedures involving alkoxysilanes were implemented in order to re-conserve the samples. The study revealed the techniques are an efficient re-conservation method in which highly satisfactory results can be achieved. The re-treated samples present minimal volumetric distortion without significant collapse or shrinkage of the wood structures. This minimal distortion is primarily produced by the transition from swollen waterlogged wood to a dry conserved wood, and not as a result of collapse or shrinkage during treatment. Due to the negligible thickness of the polymer coating (a few microns), the samples acquire physical properties extremely close to the original dry wood. Moreover, other physiochemical properties are obtained from the consolidation with alkoxysilanes; the re-conserved wood becomes hydrophobic, chemically inert, resistant to chemical attacks (e.g., acids or bases), and resistant to ultraviolet light. These newly acquired characteristics drastically reduce the preventive conservation measures needed in museum display cabinets or during transport. Despite the excellent results, the procedure is not reversible, thus does not comply with one of the main premises traditionally accepted in conservation. Therefore, a careful study assessing benefits and disadvantages in a case-by-case basis should be assessed by conservators, restorers, and curators before applying this method to waterlogged material culture