Hydrogels in Heritage Conservation: A Comparative Evaluation on Composite Objects

Ethnographic collections often incorporate composite objects consisting of various materials, including wood, textiles and metals. These objects are vulnerable to deterioration when iron fastenings corrode under humid environments, and their removal is therefore essential for the long-term preservation of artifacts. This study investigates the efficacy of the chelating agents Desferrioxamine B (DFO-B) and ethylenediaminetetraacetic acid (EDTA), applied in different gel formulations, in cleaning wooden and textile mock-ups stained with iron corrosion products. Three gel types were explored: xanthan gum, agarose and Nanorestore extra-dry gel with medium water retention (nano-MWR). The results indicated that xanthan gum exhibited the highest cleaning effectiveness but posed risks of residue deposition and surface damage due to the required clearance process. Agarose and nano-MWR gels proved to be less effective but showed potential for achieving high chelator efficacy with repeated applications. Agarose enhanced the chelators' efficacy on textiles, while nano-MWR gel performed better on even wooden surfaces. No chemical damage was detected for either substrate across gel applications. The study concludes that a single gel formulation does not achieve equivalent cleaning efficacy on the two substrates of composite objects with a defined number of applications. Agarose in a semi-rigid state enhances the efficacy of textile treatment and may achieve comparable results on wood after repeated applications. Alternatively, a combined approach using agarose for textiles and nano-MWR gel for wood may optimize chelator performance on composite artifacts.