The ocean is an unforgiving environment for any shipwreck, but sunken wooden ships are particularly susceptible to the corrosive effects of salt water and high bacteria levels. The dangers of deterioration also do not end when the archaeological remains are recovered: conservation methods such as freeze or replacement drying can make artifacts more brittle, distort their overall shape and take months to complete. But a new hydrogel, developed by researchers in China, could provide a much safer option for eradicating harmful microbes and acids in waterlogged shipwreck wood.
The new material, detailed in a study published in ACS Sustainable Chemistry & Engineeringis the result of a collaboration between several Chinese institutions, including Sun-Yat Sen University and the Hong Kong University of Science and Technology. Experts already use certain hydrogels in similar artifact recovery projects, but they must peel off the coating after it has infused the wood with curing compounds – a potentially damaging procedure in itself. However, the new substance dissolves safely after a few days without the need for immediate physical removal.
To create their material, researchers combined precise amounts of acid-neutralizing potassium bicarbonate with antimicrobial, polymer-binding silver nitrates. The substance also relied on sodium alginate, a naturally occurring polysaccharide made from brown seaweed that is often used as a thickener by the food, cosmetic and pharmaceutical industries. Once mixed together, the team then tested the hydrogel’s capabilities in a proof-of-concept using a real shipwreck wood. In this case, the samples came from an 800-year-old sunken ship, courtesy of the Guangdong Maritime Silk Road Museum.
Reachers then analyzed the preservation options after applying multiple versions of the hydrogel coating to the saltwater-laden logs. According to one Announcement on December 3Each hydrogel blend neutralized acids up to 1 centimeter deep within 10 days of application. However, hydrogels containing less silver nitrate began removing harmful chemicals after just one day. Similarly, fewer silver nitrate gels become fully liquid after three to five days, while more silver nitrate causes a coating to remain a “sticky solid,” according to the study announcement. Overall, hydrogel-treated wood was ultimately less brittle than samples treated with more solid gels.
[Related: A hunk of coal from the Titanic could fetch $780 at auction.]
“… [T]The hydrogel system is integrated [silver nitrates] demonstrates remarkable preservation effects on wooden cultural relics, in terms of solubility, ductility and antibacterial properties,” researchers write in their conclusion of the studyadding that they hope the new material can “provide a timely and multi-functional solution for the conservation of wooden cultural heritage.”