Organosilicons of different molecular size and chemical structure as consolidants for waterlogged archaeological wood – a new reversible and retreatable method

Abstract

Ineffectiveness of the chemicals applied so far for waterlogged wood conservation created the need to develop new more, efficient and reliable agents. As an alternative, a new method with the use of organosilicon compounds differing in chemical composition and molecular weight has been investigated. The results obtained show the potential of organosilicons as consolidants in waterlogged wood conservation able to effectively stabilise wood dimensions upon drying. The best wood stabilisers were low-molecular organosilicons enable to penetrate the cell wall as well as chemicals with functional groups capable of interacting with wood polymers and forming stabilising coatings on the cell wall surface. The best anti-shrink efficiency values were obtained for (3-Mercaptopropyl)trimethoxysilane, (3-Aminopropyl)triethoxysilane, 1,3-Bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, reaching 98, 91 and 91%, respectively. Most of the applied organosilicons reduced wood hygroscopicity, which limits the risk of further dimensional changes of wood exposed to a variable air moisture content and potentially reduces wood biodegradation. In the light of our studies, the proposed method of waterlogged wood conservation with organosilicons is potentially reversible in the case of siloxanes and amino-silanes as well as retreatable, which complies with the requirements of the conservation ethics.

Interactions between Different Organosilicons and Archaeological Waterlogged Wood Evaluated by Infrared Spectroscopy

“…The samples of wood treated with silane 2 (A2) present most informative bands at 1340 (8) and 1308 (8) cm −1 assigned to deformation of -CH 2 groups present in the spectra due to existence of a larger number of these groups in the solid network. Furthermore, similarly to A1, were observed bands at 1187 (10), 1130 (11), 1030 (14), 1004 (14), 918 (16), 861 (17), 807 (19), 768 (20), 692 (21), and 474 (22) cm −1 (see assignments in Table 1).…”

“…The results of the research by Broda et al [21,22] clearly showed that the stabilisation effect on waterlogged wood depends mainly on the type of an organic group attached to a silicon atom in organosilicons. Great dimensional stabilisation of waterlogged wood was obtained among other things due to methyltrimethoxysilane (MTMS), (3-mercaptopropyl) trimethoxysilane (MPTES) and 1,3-bis(diethylamino)-3-propoxypropanol)-1,1,3,3tetramethyldisiloxane (DEAPTMDS) treatment, reaching anti-shrink efficiency values of about 81%, 98% and 90%, respectively.…”

“…They have also proved to penetrate and bulk the cell wall, forming a three-dimensional network of polysiloxane and wood polymers which improves dimensional wood stability [8,13,18]. Therefore, they were also tried for archaeological waterlogged wood conservation, and some of them proved effective in stabilisation of wood dimensions upon drying, which is one of the most crucial issues related to conservation of this type of wood [19][20][21][22]. However, the method still requires further study, e.g., on the mechanical properties of the treated wood, the influence of the chemicals on wood colour, gloss and texture, or their long-term effect on wood before it could be proposed as a reliable conservation method.…”

The effect of the drying method on the cell wall structure and sorption properties of waterlogged archaeological wood

“…), excavated from debris of the mediaeval "Poznań" bridge at the bottom of the Lednica Lake (the Wielkopolska Region, Poland), was used for the study. The elm log consisted only of heartwood, and although apparently well-preserved in appearance, it proved to be severely degraded, with the loss of wood substance (LWS) estimated at 70-80% and significantly reduced hemicelluloses and cellulose content (Broda et al 2020;Spear and Broda 2020).…”

Pickering Emulsions Based on Wax and Halloysite Nanotubes: An Ecofriendly Protocol for the Treatment of Archeological Woods

“… 4 , 5 Consequently, the main concern related to the drying process is the loss of the original structure and, therefore, the loss of the historical artwork itself. 6 New protocols have been developed for the conservation of cultural heritage. 7 , 8 Colloidal engineering has become a deeply investigated research domain, and many synthetic routes have been proposed for chemists and materials scientists.…”