Oct 23 2020
Researchers at the Institut Laue-Langevin (ILL) in collaboration with a group from the University of L’Aquila (Italy), have found a new way of protecting wooden objects, such as shipwrecks, preserved for hundreds of years under our waters, but vulnerable to decay as soon as they are brought to land.
The finding will enable the preservation of priceless waterlogged artefacts, ensuring extremely rare fragments of our past can be kept for the study of archaeology, anthropology, and human history.
To preserve wooden treasures from the seafloor, it is critical to halt the degradation process as soon as excavation begins. Yet, a satisfactory solution for the deacidification of ancient wood on a large-scale had not been found. One of the world’s most famous shipwrecks, the 400-year old Vasa ship in Stockholm, was partially eaten by sulphuric acid in the early 2000s due to the ferociousness of the process – when exposed to oxygen and air humidity, an ‘infection’ can spread and make the entire structure crumble.
New research published in Nanomaterials demonstrates a ground-breaking new answer for curing the acidification ‘disease’ of ancient waterlogged wood once removed from water. While it is common to submerge wooden artefacts in a solution of polyethylene glycol (PEG) to replace the water in the structure and prevent cracking as the wood dries out – this treatment is not adapted to stop acidification, and corrosive chemicals can emerge on the wood years after treatment.
The new solution from a consortium of researchers in France and Italy uses nanoparticles which enter the pores of wood and generates a buffer to prevent the creation of acids. They used neutron scattering and X-ray diffraction to reveal the effectiveness of the treatment on a 2,000 year-old Gallo-Roman barge at the Lugdunum museum (Lyon, France) on loan from ARC-Nucléart (Grenoble, France), focused on the stability and safety of the nanoparticles in water.
Nanoparticle products have been of interest to cultural heritage research for some time, however existing solutions are very expensive and potentially damaging to humans and the environment. Many involve alcohol as a solvent – a very volatile and flammable chemical – and so when used on a large-scale (e.g. for shipwrecks which require 12 x 6m pools for submersion) they pose huge risk as well as an increasing cost. A new innovative solution found by researchers at the University of L’Aquila led by Prof. G. Taglieri, was able to produce and use nanoparticles directly in water – an inexpensive, accessible and safe solvent. An exciting, sustainable, scalable, eco-friendly and low-cost route, this solution has the potential to transform traditional conservation methods.
A technique called small angle neutron scattering (SANS) was applied at the Institut Laue-Langevin (ILL), the world’s flagship centre for neutron science, to examine and compare the suspension of calcium- and magnesium-hydroxide nanoparticles in water. This confirmed that the particles would be free to move into the wood and successfully deacidify. Several techniques, including atomic force microscopy (using the PSCM platform), electron microscopy and X-ray probing, were then used to study the structure of nanoparticles and evidence of degradation in the wood samples following the selection of preventative and curative treatments.
Neutrons are an important tool in cultural heritage studies, as they are non-destructive and can penetrate deep into solid or, uniquely, liquid materials to reveal what is happening at the atomic or molecular level. They can reveal metal manufacturing methods used on ancient swords, or improve the restoration processes used on centuries-old works of art.
The novel treatment is both curative and preventative of the acidification seen in wooden artefacts and can help to maintain the original structure and appearance of the relic. This research will open the doors to safe and sustainable preservation of human history in the form of sunken ships and bridges and enable future generations to learn from and appreciate the creations of ancient societies.
Claudia Mondelli, Scientist from the Consiglio Nazionale delle Ricerche at ILL, said “The findings from the combined neutron and X-ray techniques confirm the hugely exciting potential of nanotechnology in conservation science. These cutting-edge techniques are invaluable for helping us understand how we can alleviate and prevent damage to ancient objects, allowing us to extract information about how societies lived, worked, and constructed when the object was used, whilst preserving them for generations to come.”
Gilles Chaumat, Coordinator of Research Programs at ARC-Nucleart said “Finding affordable, sustainable, and effective treatments is a huge challenge in conservation of wooden objects, a field we specialise in. The advanced non-destructive analytical techniques used in this research help us understand what is safe to use on these precious artefacts and allow us to protect more of human history through our work.”
Sustainable Nanotechnologies for Curative and Preventive Wood Deacidification Treatments: An Eco-Friendly and Innovative Approach, G. Taglieri, V. Daniele, L. Macera, R Schweins, S. Zorzi, M. Capron, G. Chaumat, C. Mondelli [doi:10.3390/nano10091744]