New hydrogel could preserve waterlogged wood from shipwrecks
From the Titanic to the Endurance, shipwrecks provide us with valuable windows into the past, but they are deteriorating rapidly. Conservators slowly dry marine wooden artifacts to preserve them, but doing so can cause damage. To better care for delicate marine artifacts, researchers ACS Sustainable Chemistry and Engineering A new hydrogel has been developed that can quickly neutralize harmful acids and stabilize waterlogged wood from an 800-year-old shipwreck.
The wooden artifacts in the wrecks were soaked with seawater, an environment that allowed acid-producing bacteria and wood-eating fungi to thrive. To prevent acid and microbial damage, conservators often remove moisture from these artifacts through freeze-drying or a process that uses high-pressure carbon dioxide or viscous polymers instead of water. However, these processes can take months and can increase brittleness or deformation of the workpiece. A newer alternative is to coat damp historic wood with a gel that acts like a face mask, infusing the wood with acid-neutralizing or antimicrobial compounds. But removing the mask later may damage the surface of the item. So Xiaohang Sun and Qiang Chen set out to develop a hydrogel that could disperse acid-resistant and antimicrobial compounds into wood and gradually dissolve them over time to avoid surface damage.
The researchers first mixed the two polymers with potassium bicarbonate (an acid-neutralizing compound) and silver nitrate to form antimicrobial nanoparticles that linked the polymers together to form a gel. By adjusting the amount of silver nitrate, they were able to create hydrogels with varying staying power. Gels containing less silver liquefied after 3-5 days, while gels containing more silver remained a viscous solid.
As a proof-of-concept approach, the team attached hydrogels containing varying amounts of silver to 800-year-old wood from the Nanhai-1 shipwreck found off the coast of southern China. They found that each gel neutralized acid to a depth of 1 centimeter after 10 days, but the dissolving gel containing less silver neutralized faster after 1 day. The team also found that artifacts treated with liquefied gel retained their cellular structure better and were less fragile than artifacts treated with solid gel. The researchers say their new hydrogel could be used to preserve and strengthen wood from shipwrecks without causing additional damage, increasing the ability to unravel mysteries of the past.
The authors thank the National Natural Science Foundation of China and the Guangdong Basic and Applied Basic Research Fund for funding.
2024-12-03 20:43:37